WO2017029629A1

WO2017029629A1 - Improvements to electrically operable resuscitators

Info

Publication number: WO2017029629A1
Application number: PCT/IB2016/054939
Authority: WO
Inventors: Gilbert Jacobus Kuypers; Richard Anthony Mcculloch
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-08-18
Filing date: 2016-08-18
Publication date: 2017-02-23
Anticipated expiration: 2018-02-18

Abstract

The invention relates to a resuscitator method and apparatus that receives one or more patient details, and controls a motor to move a piston to deliver an initial tidal volume during an initial respiratory cycle that is smaller than a best practice tidal volume associated with said one or more patient details, and controls the motor to move the piston to deliver an incrementally increased tidal volume in subsequent respiratory cycles, until the delivered tidal volume in a respiratory cycle is equal to the best practice tidal volume.

Description

IMPROVEMENTS TO ELECTRICALLY OPERABLE RESUSCITATORS

FIELD OF THE INVENTION

The present invention relates to improvements to resuscitators. More particularly but not exclusively it relates to electrically controlled resuscitators.

BACKGROUND TO THE INVENTION

Resuscitators that can supply pressurised air or oxygen to a patient are well-known. Examples include bag or bellows type resuscitators and pump-like resuscitators and pressure-limited resuscitators. However, there are limitations in certain resuscitators.

For example, there is a risk of overinflating a patient's lungs by delivering a volume of air that is greater than desirable. There is also a risk the pressure of the air or oxygen delivered may be at undesirably high levels. Such undesirable characteristics of the air being delivered to the patient can have adverse affects on the patient. If a patient's airway passage is or becomes blocked and air is delivered by the known devices then undesirable pressures may be reached. Further such increased pressure may cause sudden dislodgement of the blockage and may lead to serious consequences for the patient. Known devices do not readily lend themselves to predetermination of airway pressures and volumes to which the lungs of the patient are being subjected by the operator of the device. The operator may feel a resistance when they are applying a force to the device to deliver air or oxygen. The operator may increase the force to overcome the blockage. However, when the blockage clears there is a risk of over- pressurising or overfilling the lungs, thereby causing barotrauma or volutrauma or both.

Eliminating human operation of a resuscitator for delivering air to a patient is advantageous. By eliminating the operator the risk of delivering too great a volume of air into the patient and overinflating the patient's lungs, causing volutrauma, is reduced. By eliminating the operator the risk of delivering too great a pressure of air into the patient and therefore over pressurising the patient's lungs, causing barotrauma, is reduced. In resuscitation it is desirable to start at the lowest risk procedure to the patient. The lowest risk procedure is volume resuscitation rather than pressure-limited resuscitation or manual-controlled resuscitation.

In known devices there is the risk that an operator may displace too great a volume of air into the patient and therefore overinflate the patient's lungs. There is also the risk of applying a pressure that is too great or insufficient for the patient's lungs. For example, when the airway passage is blocked, prior art systems do not signal that the operator should stop and remove the blockage.

It would therefore be an advantage to provide improvements to resuscitators that address or go at least some way towards addressing at least some of the abovementioned disadvantages and/or addresses at least some of the abovementioned advantages or that will at least provide the public or industry or both with a useful choice. SUMMARY OF THE INVENTION

In a first aspect the present invention consists in a pump for a

resuscitation device comprising :

• a rigid cylinder including at least one gas inlet and at least one gas outlet,

• a piston movable in said cylinder in a reciprocating manner in at least a first stroke direction and a second stroke direction, and

• at least one valve assembly configured for allowing gas to be drawn into said cylinder through said at least one gas inlet when the piston is moving in a first stroke direction in said cylinder, and for allowing gas to be displaced through said at least one gas outlet when the piston is moving in a second stroke direction;

• an accurate positional control motor operatively connected to said piston to move said piston in said cylinder;

• a controller comprising digital storage media for storing digital instructions and configured for controlling the motor to control the position of the piston in the cylinder to thereby control

• the tidal volume of the gas delivered to a patient; and

• the pressure of the gas delivered to the patient; according to

established medical best practices for a patient.

In one embodiment, the controller is configured for receiving data inputs relating to the patient.

In one embodiment, the controller is configured for receiving inputs including one or more selected from

• the age of the patient,

• the length of the patient and

• the weight of the patient.

In one embodiment, the pump comprises at least one receiver for receiving input signals from a transducer.

In one embodiment, the pump comprises at least one receiver for receiving input signals from one or more selected from

• a pressure transducer;

• a distance transducer;

• a flow sensor; • a carbon dioxide sensor;

• a resistance detector;

• a voltage detector; and

• a current detector.

In one embodiment, the pump comprises at least one receiver for receiving input signals from a pressure transducer measuring the pressure in a patient interface.

In one embodiment, the receiver is configured for receiving updated instructions, including updated best practice tidal volumes, respiratory rates and gas pressures for a group of patients.

In one embodiment, the pump comprises a transmitter for sending output signals including treatment details of a patient.

In one embodiment, the details of treatment include one or more selected from :

• the patients name;

• the patients weight;

· the patient's age;

• the respiratory rate delivered over time;

• maximum and/or minimum respiratory rates;

• the tidal volumes delivered over time;

• maximum and/or minimum tidal volumes

· the pressure fluctuations in the patient interface and/or piston over time; and

• maximum and/or minimum pressures.

In one embodiment, the instructions are configured for directing the controller to control the position of the motor in response to detected pressures from the pressure transducer.

In another aspect the present invention consists in a pump for a

resuscitation device comprising :

• a primary gas displacement device configured for displacing gas towards a patient interface at intermittent compression cycles;

· a secondary pressurisation device configured for providing a pressurised gas at a constant pressure to a patient interface;

• wherein the primary gas displacement device and the secondary pressurisation device are connected or connectable to a patient interface in a manner whereby the constant pressure provided by the secondary pressurisation device is made available to the patient between the intermittent compression cycles of the primary gas displacement device. In one embodiment, the primary gas displacement device is controllable to vary one or more selected from the tidal volume, the pressure and the respiratory rate of gas delivered to a patient in at least each inspiratory cycle.

In one embodiment, the primary gas displacement device comprises

· a rigid cylinder including at least one gas inlet and at least one gas outlet,

· a controller configured for controlling the motor to control the position of the piston in the cylinder to thereby control

• the tidal volume of the gas delivered to a patient; and

• the pressure of the gas delivered to the patient;

• wherein the primary gas displacement device is engaged or engageable in fluid communication with a patient interface suitable for ducting gas to a patient;

In one embodiment, the secondary pressurisation device is a blower.

In one embodiment, the secondary pressurisation device is configured to receive gas from a gas source. In one embodiment, the gas source is an oxygen tank. In one embodiment, the instructions are configured for directing the controller to carry out the steps of:

• receiving a tidal volume signal indicative of the tidal volume of gas required to be delivered to a patient; and

• determining the number and/or length of strokes and/or proportion of strokes of the piston required to provide the required tidal volume to the patient.

In one embodiment, the instructions are configured for directing the controller to carry out the steps of:

• stopping movement of the linear motor during an exhalation period of the patient.

In one embodiment, the instructions are configured for directing the controller to carry out the steps of: • controlling the linear motor to move the piston in an opposite direction to the direction the piston moved during the inhalation stroke.

· receiving a pressure signal indicative of the pressure in the patient interface; and

• controlling movement of the linear motor to control movement of the piston to keep a minimum pressure in the patient interface above a predetermined threshold.

• controlling movement of the linear motor to control movement of the piston to keep a minimum pressure in the patient interface above a predetermined threshold for a predetermined time period.

• comparing the received pressure signal over time to determine whether the pressure reduces in the patient interface.

• if the result of the determination is that the initially generated pressure was not released by a predetermined period, controlling the motor to accelerate the piston to generate an incrementally higher pressure in the patient interface.

• if the pressure of the gas in the patient interface has been released with a predetermined period, controlling the motor to move the piston to sustain a delivery of gas at one or more selected from a predetermined pressure, a predetermined tidal volume and a predetermined volume flow rate, until the set maximum piston stroke length has been reached, after which the piston is stopped.

· comparing the rate of change of pressure in the patient interface to

predetermined thresholds.

In one embodiment, the instructions are configured for directing the control ler to carry out the steps of: • detecting whether the initial pressure or subsequent incremental pressures of the gas in the patient interface are released by inflation of the patients lungs within a predetermined period, and

• if the initially generated pressure of the gas in the patient interface has been released, controlling the motor to move the piston to sustain a delivery of gas at one or more selected from a predetermined pressure, a predetermined tidal volume and a predetermined volume flow rate, until the pressure of the gas in the patient interface rises to a predetermined threshold, after which the piston is stopped.

• detecting whether the initial pressure or subsequent incrementally higher pressures of the gas in the patient interface are released by inflation of the patients lungs within a predetermined period, and

· if the initially generated pressure of the gas in the patient interface has been released, controlling the motor to move the piston to sustain a delivery of gas at one or more selected from a predetermined pressure, a predetermined tidal volume and a predetermined volume flow rate, until the pressure of the gas in the patient interface rises to a predetermined threshold, after which the piston is stopped.

• determining the rate of release of pressure in the patient interface over time;

· comparing the rate of release of pressure in the patient interface with

predetermined thresholds.

• controlling the motor to move the piston to sustain a delivery of at one or more selected from a predetermined pressure, a predetermined tidal volume and a predetermined volume flow rate in accordance with the comparison of the of the rate of release of pressure in the patient interface with predetermined thresholds.

• controlling the motor to move the piston to sustain a delivery of gas at one or more selected from a predetermined pressure, a predetermined tidal volume and a predetermined volume flow rate in accordance with the maximum pressure exerted before the pressure was released.

· controlling the motor to move the piston to sustain a delivery of gas to a predetermined maximum tidal volume in accordance with the comparison of the rate of release of pressure in the patient interface with predetermined thresholds.

In one embodiment, the predetermined thresholds for tidal volumes, pressures and respiratory rates are predetermined according to best practice.

In one embodiment, the predetermined thresholds for tidal volume, respiratory rate and pressure are determined by the controller as directed by the instructions in accordance with received patient details.

• receiving patient details relating to one or more selected from the patient's age, weight or length

· interrogating a data store using the received patient

• receiving an initial predetermined tidal volume signal indicative of an initial predetermined tidal volume to be delivered to the patient from a data store as a result of the interrogation.

• receiving a maximum best practice pressure signal indicative of a

maximum best practice pressure from a data store as a result of the interrogation, and

• setting a maximum best practice pressure in the patient interface from the maximum best practice pressure signal .

• receiving a best practice tidal volume signal indicative of a best practice total volume from a data store as a result of the interrogation.

• receiving a tidal volume increment signal from a data store as a result of the interrogation. In one embodiment, the instructions are configured for directing the controller to carry out the steps of:

• receiving a subsequent pressure signal indicative of one or more selected from the pressure in the patient interface and the pressure in the patient airways after delivery of the initial tidal volume.

• comparing the patient pressure signal and the maximum best practice

pressure signal.

• generating an alert signal if the comparison indicates that the patient

pressure signal is equal or exceeds the maximum best practice pressure signal.

• comparing the best practice tidal volume to the subsequent tidal volume. In one embodiment, the instructions are configured for directing the controller to carry out the steps of:

• if the subsequent tidal volume is equal to and/or within a predetermined range of best practice tidal volume, and the patient pressure does not exceed the maximum best practice pressure, delivering a subsequent tidal volume at the best practice tidal volume.

• if the maximum best practice pressure has been exceeded and the best last delivered subsequent tidal volume is not equal to or within a predetermined range of the best practice tidal volume, presenting an operator with an option of allowing a manual override of the maximum best practice pressure to a manual pressure.

• controlling movement of the linear motor to move the piston to deliver one or more inspiratory cycles at a the manual pressure set by the operator.

In one embodiment, the number of inspiratory cycles delivered at the manual pressure is predetermined, after which the controller starts delivering subsequent tidal volumes at the maximum best practice pressure again. In one embodiment, the instructions are configured for directing the controller to carry out the steps of:

• controlling movement of the motor to move the piston to deliver a tidal volume to a patient at a constant target pressure.

• delivering an initial tidal volume to a patient during an initial respiratory cycle;

• delivering a subsequent tidal volume to a patient during a subsequent

respiratory cycle;

• receiving an initial airway pressure signal and a subsequent airway pressure signal indicative of the initial airway pressure in the patient's airway after delivery of the initial tidal volume and the subsequent airway pressure after delivery of the subsequent tidal volume respectively; and

· determining the airway pressure difference between the initial airway

pressure and the subsequent airway pressure.

• receiving a target pressure signal indicative of the target pressure.

• interrogating a data store for a target pressure.

In one embodiment, the step of interrogating a data store for a target pressure comprises the step of:

· transmitting one or more selected from

o the initial airway pressure

o the subsequent airway pressure

o the airway pressure difference.

In one embodiment, the instructions are configured for directing the controller to carry out the step of:

• controlling movement of the motor to control movement of the piston to stop delivery of further gas to the patient if patient airway pressure exceeds a maximum pressure threshold.

• retrieving an initial predetermined tidal volume setting from a data store. In one embodiment, the instructions are configured for directing the controller to carry out the steps of: • receiving an initial pressure signal indicative of one or more selected from the pressure in the patient interface and the pressure in the patient airways; and

• controlling movement of the linear motor to move the piston to deliver an initial tidal volume.

In one embodiment, the delivered initial tidal volume is the initially predetermined tidal volume.

· receiving a subsequent pressure signal indicative of one or more selected from the pressure in the patient interface and the pressure in the patient airways after delivery of the initial tidal volume.

· comparing the initial pressure signal and the subsequent pressure signal.

In one embodiment, the step of comparing the initial pressure signal and the subsequent pressure signal may include determining the rate of change of pressure.

· determining a tidal volume increment in accordance with the comparison of the initial pressure signal and the subsequent pressure signal.

In one embodiment, the determination of the tidal volume increment is by interrogating a data store using the comparison of the initial pressure signal and the subsequent pressure signal.

• interrogating a data store for a tidal volume corresponding to the

comparison of the initial pressure signal and the subsequent pressure signal.

In one embodiment, the step of determining the tidal volume increment is by retrieving a tidal volume increment from a data store

• determining a subsequent tidal volume to be delivered to a patient.

In one embodiment, the subsequent tidal volume is the initial tidal volume plus the tidal volume increment.

In one embodiment, the instructions are configured for directing the controller to carry out the step of: • controlling movement of the motor to move the piston to deliver a subsequent tidal volume.

· controlling movement of the motor to move the piston to move at a

relatively high respiratory rate and a relatively low tidal volume;

• controlling the movement of the linear motor to incrementally increase the tidal volume delivered via the patient interface.

• receiving a pressure signal indicative of the pressure in the patient interface. In one embodiment, the instructions are configured for directing the controller to carry out the steps of:

• controlling movement of the motor to decelerate or stop the piston when the pressure signal reaches a predetermined threshold pressure.

• controlling movement of the motor to deliver the same tidal volume during an inspiratory cycle of the patient as was delivered before the

predetermined threshold pressure was reached.

• transmitting an alert signal in order to alert an operator that a

predetermined threshold pressure has been reached.

In one embodiment, the alert signal is displayed on a screen instructions are configured for directing the controller to carry out the steps of:

• providing a manual override option to an operator, whereby one or more selected from the tidal volume, the inspiratory pressure being delivered by the pump and the respiratory rate is manually settable..

• determining a rate of change of pressure signal indicative of the rate of change of the pressure in the patient interface from the pressure signal.

• controlling movement of the motor to decelerate or stop the piston when the rate of change of pressure signal in the patient interface reaches a predetermined threshold.

In one embodiment, the instructions are configured for directing the controller to carry out the steps of: • receiving a best practice initial respiratory rate signal indicative of a best practice initial respiratory rate from a data store.

• receiving a best practice initial respiratory rate signal indicative of a best practice initial respiratory rate from a data store.

• controlling movement of the motor to move the piston to deliver consecutive tidal volumes at an initial respiratory rate.

• receiving a patient pressure signal from a pressure transducer indicative of the pressure in the patient interface and/or patient airway at the end of an expiratory cycle.

• interrogating a data store for a best practice ramping pressure signal.

• receiving a best practice ramping pressure signal from a data store. In one embodiment, the instructions are configured for directing the controller to carry out the steps of:

• comparing the patient pressure to a threshold ramping pressure.

• retrieving a respiratory rate increment signal indicative of a best practice change of respiratory rate, from a data store.

In one embodiment, the step of retrieving the respiratory rate increment signal is carried out by interrogating a data store using one or more selected from :

• the rate of change of pressure,

• the pressure difference

• determining a subsequent respiratory rate. In one embodiment, the instructions are configured for directing the controller to carry out the steps of:

• determining a subsequent respiratory rate using the respiratory rate

increment signal.

In one embodiment, the step of determining the subsequent respiratory rate is by subtracting the respiratory rate increment from the last respiratory rate.

• controlling the motor to move the piston to move at the subsequent

respiratory rate

• receiving a predetermined ramping pressure signal from a data store.

• receiving a pressure signal from a pressure sensor in one or more selected from the patient interface and the patient's airway.

· controlling movement of the motor to move the piston to deliver an initial tidal volume during an inspiratory phase of a patient.

• controlling movement of the motor to move the piston to stop or retract during an expiratory phase of the patient.

• comparing the received pressure signal from the pressure sensor to the ramping pressure signal.

• timing the expiratory cycle as a time signal.

· retrieving an expiratory cycle time threshold signal indicative of the

maximum time limit of the expiratory cycle of a patient.

In one embodiment, the instructions are configured for directing the controller to carry out the steps of: • determining an expiratory cycle time threshold signal indicative of the maximum time limit of the expiratory cycle of a patient.

• comparing the time of the expiratory cycle to the expiratory cycle time

threshold signal.

• generating an alert signal if the time of the expiratory cycle exceeds the expiratory cycle time threshold signal.

• controlling movement of the motor to move the piston to move the piston to deliver a subsequent tidal volume during an inspiratory phase of a patient, if the received pressure signal has dropped to a level equal to or below the received ramping pressure signal.

In one embodiment, the instructions are configured for directing the controller to determine a signal indicative of the pressure in the patient interface.

In one embodiment, the signal indicative of the pressure in the patient interface is determined using signals indicative of one or more of

• the voltage across at least part of the linear motor;

• the current through at least part of the linear motor;

• the power being used by the linear motor.

In one embodiment, the instructions are configured for directing the controller to control the pressure generated by the piston by controlling one or more selected from

• the power of the linear motor,

• the voltage provided to at least a part of the linear motor, and

• the current supplied to at least a part of the linear motor.

In one embodiment, the instructions are configured for directing the controller to control the maximum pressure exertable by the piston by limiting one or more selected from

• the power of the linear motor,

• the voltage provided to at least a part of the linear motor, and

• the current supplied to at least a part of the linear motor.

• controlling the movement of the motor to move the piston in at least one direction at a controlled average velocity, while accelerating and decelerating the piston to provide a series of pressure pulses as the piston moves along at the said controlled average velocity.

· receiving a patient pressure signal indicative of the pressure of the gas at or about one or more selected from the patient interface and the patient's airways.

· receiving a maximum pressure signal from a data store.

In one embodiment, the received maximum pressure signal is received in response to an interrogation of the data store for a maximum pressure signal corresponding to input patient's details.

• interrogating a data store for a maximum pressure signal corresponding to input patient's details.

· comparing the patient pressure signal to the received maximum pressure signal.

• controlling the motor to control movement of the piston to ensure that the patient pressure signal including the pressure pulses, does not exceed the received maximum pressure signal.

• receiving an inlet pressure signal indicative of the pressure of the gas at or about the inlet.

• determining or retrieving a tidal volume to be delivered to the patient at ambient pressure.

• determining a compensated tidal volume to be delivered at the inlet

pressure, and; • controlling movement of the motor to accelerate the piston to deliver the compensated tidal volume to one or more selected from a patients airways and the patient interface.

In one embodiment, the step of determining a compensated tidal volume comprises the step of interrogating a data store for one or more selected from

• calculating a compensation factor from a set of associated parameters; and

• a compensated tidal volume from a set of associated parameters.

· a compensation factor associated with the inlet pressure signal; and

• a compensated tidal volume.

In one embodiment, the step of interrogating the data store comprises transmitting a set of associated parameters to retrieve an associated

• a compensation factor associated with the inlet pressure signal; and

· a compensated tidal volume.

In one embodiment, the associated parameters may comprise one or more of

• inlet pressure,

• best practice tidal volume to be delivered,

• ambient pressure,

· ambient temperature,

• temperature at the inlet;

• flow velocity at the inlet,

• or the like.

In one embodiment, the patient interface comprises a flow sensor.

In one embodiment, the flow sensor is configured for sending a flow signal indicative of the flow arte through the patient interface.

In one embodiment, the controller is configured for receiving the flow signal.

· receiving a flow signal from a flow transducer.

• integrating the flow sensor readings over time to determine a volume.

• integrating the flow sensor readings from the start of the inspiration cycle of a patient to the end of the inspiration cycle of a patient to determine a patient tidal volume. In one embodiment, the instructions are configured for directing the controller to carry out the steps of:

• determining the volume of gas delivered by the piston to the patient

interface as a pumped volume.

• comparing the pumped volume to the patient tidal volume.

· transmitting an alert signal in the vent that the patient tidal volume and the pumped volume do not coincide with each other.

• determining the difference between the pumped volume and the patient tidal volume.

• controlling the motor to control movement of the piston to increase or decrease the pumped tidal volume in accordance with the determination of the difference between the pumped volume and the patient tidal volume.

• receiving an initial patient pressure signal indicative of the pressure in one or more of the patient interface and the patient's airways during an expiratory cycle of the patient.

• receiving a subsequent patient pressure signal indicative of the pressure in one or more of the patient interface and the patient's airways during an expiratory cycle of the patient.

In one embodiment, the instructions are configured for directing the controller to carry out the steps of: • comparing the initial patient pressure signal and the subsequent patient pressure signal.

· determining if the subsequent patient pressure signal has dropped below the initial patient pressure signal by a predetermined amount.

• actuating movement of the motor to move the piston to pump gas to the patient to start an inspiratory cycle of the patient if the subsequent patient pressure signal has dropped below the initial patient pressure signal by a predetermined amount.

· receiving an initial patient flow rate signal indicative of the gas flow rate in one or more of the patient interface and the patient's airways during an expiratory cycle of the patient.

· receiving a subsequent patient flow rate signal indicative of the flow rate in one or more of the patient interface and the patient's airways during an expiratory cycle of the patient.

· comparing the initial patient flow rate signal and the subsequent patient flow rate signal.

• determining if the subsequent patient flow rate signal has changed relative to the initial patient flow rate signal by a predetermined amount, or changed direction.

In one embodiment, the instructions are configured for directing the controller to carry out the steps of retrieving the predetermined amount from a data store.

• actuating movement of the motor to move the piston to pump gas to the patient to start an inspiratory cycle of the patient if the subsequent patient flow rate signal has changed relative to the initial patient flow rate signal by a predetermined amount, or changed direction.

• determining the rate of change of the pressure over time between the initial pressure signal and the subsequent pressure signal; and

• controlling movement of the motor to move the piston based on the

determination of the rate of change of pressure over time.

• determining the length of time that the expiratory cycle has been ongoing. In one embodiment, the instructions are configured for directing the controller to carry out the steps of:

• comparing the time that the expiratory cycle has been ongoing and the predetermined maximum expiratory time.

• generating an alert signal if the length of the expiratory cycle is equal to or exceeds predetermined maximum expiratory time..

• actuating movement of the motor to move the piston to pump gas to the patient to start an inspiratory cycle of the patient if the expiratory cycle is equal to or exceeds predetermined maximum expiratory time.

In one embodiment, the patient interface comprises a gas level sensor.

In one embodiment, the controller is configured to receive a gas level signal from a gas level sensor.

• receiving a gas level signal from a gas level sensor.

• receiving a predetermined best practice gas level range from a data store. In one embodiment, the instructions are configured for directing the controller to carry out the steps of:

• interrogating a data store based on input patient's details for one or more selected from a best practice gas level range and a best practice gas level. In one embodiment, the instructions are configured for directing the controller to carry out the steps of:

• comparing one selected from the received gas level signal and the said one or more selected from best practice gas level range and the best practice gas level signal.

In one embodiment, the instructions are configured for directing the controller to carry out one or more selected from the steps of:

• transmitting an alert signal if the received gas level signal does not fall within the best practice gas level range; and

· transmitting an alert signal if the received gas level signal does not

substantially correlate with the best practice gas level signal.

In one embodiment, the gas level sensor is one or more selected from a :

• carbon dioxide sensor;

• carbon monoxide sensor;

· nitrogen sensor;

• or the like

In one embodiment, the pump comprises a blower arrangement for providing a minimum CPAP pressure.

In one embodiment, the pump and the blower are configured to cooperate together in operation to ensure that a minimum predetermined pressure is always provided to one or more selected from the patient interface and the patient.

Preferably wherein intermediate of the patient interface and the at least one outlet of the cylinder and in said ducted fluid connection therewith is a gas flow controller.

Preferably the gas flow controller includes a one way valve that allows gas to be displaced from the outlet of the cylinder towards the patient interface and prevents gas from flowing through the one way valve in the opposite direction.

Preferably the gas flow controller includes a valved exhaust port via which gas can exhaust to relieve pressure at the patient interface.

Preferably said valved exhaust port assumes a closed condition when the piston is moving in a direction to displace gas towards the patient interface and assumes an open condition when the piston is moving in the opposite direction to allow gas due to exhalation of or by the patient to pass through the exhaust port.

Preferably said valved exhaust port includes at least one opening closable by a valve, said valve mounted on or to or in operative association with an actuator to actively control the movement of the valve relative the opening.

Preferably said valved exhaust port includes at least one opening closable by a valve, said valve mounted for movement relative the opening in a passive manner under the influence of pressure differential in the gas from controller and/or between the gas flow controller and ambient gas pressure.

Preferably said valved exhaust port is moved to a closed condition when gas is to be displaced into said patient and to an open condition to allow gas due to exhalation of or by the patient to pass through the exhaust port.

Preferably said valved exhaust port includes at least one opening closable by a valve, said valve mounted on or to or in operative association with an actuator to actively control the movement of the valve relative to the opening.

Preferably, the actuator is a voice coil actuator.

Preferably when the valved exhaust port is in the open condition, said motor stops or reduces the velocity of the piston.

Preferably a controller is coupled to said motor to control at least the velocity and position of the motor to thereby control movement of the piston in the cylinder.

Preferably said controller is coupled to said actuator to move said actuator preferably in a manner in synchronicity with control of said motor.

Preferably said source of electricity is connected or connectable to said motor via said controller.

Preferably via an interface, the controller can be instructed to operate the device in a suitable manner.

Preferably the interface allows for patient-related information to be entered into the controller, the information including at least one selected from a patient's age, length and weight.

Preferably the controller receives data from other parts of the device, including at least one of gas pressure at the patient interface and tidal volume delivery at the patient interface.

Preferably a display is provided to display operating conditions of said device.

Preferably the operating conditions displayed may include

• inlet gas pressure,

• outlet gas pressure,

• patient airway gas pressure,

· patient interface gas pressure,

• tidal volume delivery,

• piston stroke rate,

• piston stroke length, • battery power,

• flow rates in any one or more selected form the patient interface, patient airway, and outlet;

• carbon dioxide sensor readings in any one or more selected from the patient interface, patient airway, and outlet;

• duration of operation.

Preferably the operating conditions may also be recorded for subsequent reference.

Preferably fluid connection between said outlet of said cylinder and the patient interface is defined in part by a flexible conduit.

Preferably fluid connection between said outlet of said cylinder and the patient interface is defined in part by a flexible conduit and said flow controller is located more proximate said patient interface than said cylinder.

Preferably the ducted fluid connection and/or the patient interface includes a pressure relief valve to allow pressure reduction of gas in said patient interface.

Preferably the pressure relief valve becomes operative to relieve pressure when the pressure in said patient interface reaches a certain threshold.

Preferably said pump includes an inlet volute.

Preferably the inlet volute includes an opening to allow pressure relief of said inlet volute to occur.

Preferably said inlet volute includes a one way valve to allow pressure relief to occur into the inlet volute.

Preferably the said inlet volute includes a pressure relief valve to allow pressure relief to occur out of said inlet volute.

Preferably said inlet of said cylinder is in fluid connection with a supplementary gas supply to allow supplementary gas from said supplementary gas supply to pass into said cylinder for subsequent delivery to the patient. More preferably, the supplementary gas is oxygen.

Preferably said cylinder is split into two zones by said piston, a first zone being on one side of said piston and a second zone being on the other side of said piston and wherein said gas inlet(s) are provided to allow gas into the first zone and said gas outlet(s) are provided to allow gas out of said second zone, wherein a one way pump valve is provided to allow gas to transfer from said first zone to said second zone and that restricts flow in the opposite direction.

Preferably the one way pump valve is carried by the piston to operate on a passage through the piston.

Preferably gas in said first zone, is or becomes pressurised sufficiently to, upon the movement of the piston in its first stroke direction, allow some of the gas to displace through the one way pump valve into the second zone. Preferably the one way pump valve is a passive one way valve that moves between an open and closed condition dependent on pressure differential across the one way pump valve.

Preferably a one way valve (inlet one way valve) may be provided to allow gas to be drawn into the first zone upon the movement of the piston in its second stroke direction and that restricts flow of gas in the opposite direction through said inlet one way valve upon the movement of the piston in the first stroke direction.

Preferably the inlet one way valve is a passive one way valve that moves between an open and closed condition dependent on pressure differential across the inlet one way valve.

Preferably one or each of the one way valves mentioned are valves under active control to be in the open and closed conditions in correspondence with the direction of movement of the piston.

Preferably the cylinder and piston stroke length are of a size to allow a sufficient volume of gas to be displaced from said cylinder through said gas outlet(s) during said second direction of movement of the piston to deliver a desired volume and flow rate of gas for a single inhalation to a neonatal patient for resuscitation purposes.

Preferably said cylinder is split into two zones by said piston, a first zone being on one side of said piston and a second zone being on the other side of said piston, and wherein the pump is a double acting pump that includes:

* a first one way valve to

® allow gas to enter into the first zone via a said gas inlet (herein after "first gas inlet") of said cylinder during movement of the piston in its second direction of movement, and

» restrict gas flow in the opposite direction through said first gas inlet during movement of the piston in the first direction of movement

* a second one way valve to

® allow gas to exit the first zone via a said gas outlet (herein after "first gas outlet") of said cylinder during movement of the piston in its first direction of movement, and

® restrict gas flow in the opposite direction through said first gas outlet during movement of the piston in the second direction of movement

* a third one way valve to

® allow gas to enter into the second zone via a said gas inlet (herein after "second gas inlet") of said cylinder during movement of the piston in its first direction of movement, and ® restrict gas flow in the opposite direction through said second gas inlet during movement of the piston in the second direction of movement

* a fourth one way valve to

® allow gas to exit the second zone via a said gas outlet (herein after "second gas outlet") of said cylinder during movement of the piston in its second direction of movement, and

• restrict gas flow in the opposite direction through said second gas outlet during movement of the piston in the first direction of movement

® a manifold or ducting to duct gas from said first and second outlets to said patient interface.

Preferably each of at least one of the first to fourth one way valves are either actively controlling or passive in moving between their open and closed conditions.

Preferably the cylinder and piston stroke length are of a size, and the motor is able to move and be controlled, to allow a sufficient volume of gas to be displaced from said cylinder through said gas outlet(s) during multiple oscillations of the piston to deliver a desired volume and flow rate of gas for a single inhalation to a patient for resuscitation purposes or ventilation purposes or both.

Preferably the pump is a double acting pump and the motor is of a sufficient speed to, in multiple stokes of the piston, deliver a single tidal volume of gas for a single inhalation to a patient for ventilation and/or resuscitation purposes.

Preferably the device is portable.

Preferably at least one of the pump and patient interface and motor are portable and preferably unitary and preferably able to be held in one hand by a user.

Preferably at least one of the controller and power supply and display are also portable and preferably unitary and preferably able to be held in one hand by a user.

Preferably communication to and from the controller may be wireless.

Preferably, the pump comprises a plurality of pumping assemblies, with each pumping assembly comprising a piston movable within a cylinder in a reciprocating fashion.

In one embodiment, the plurality of pistons are connected to the motor.

In one embodiment, each pumping assembly comprises a first one way valve and a second one way valve.

In one embodiment, the first one way valve is configured for allowing air into a compression zone in the corresponding cylinder when the piston is moving in one direction, and the second one way valve is for allowing compressed gas to exit from the compression zone for guidance towards a patient interface when the piston is moving in an opposite direction. In one embodiment, the pistons define one or more selected from an aperture and a recess for facilitating flow of gas into the compression zone.

Alternately, the cylinder defines one or more selected from an aperture and a recess for facilitating flow of gas into the compression zone.

In one embodiment, the first one way valve is located on the piston, and facilitates flow of gas through said one or more selected from an aperture and a recess.

In one embodiment, each of the second one way valves is disposed at an outlet to their corresponding cylinders.

In one embodiment, the motor is a linear motor, and the pumping assemblies are disposed at opposite ends of the linear motor.

In one embodiment, the pistons are each coupled to the linear motor.

In one embodiment, the pump comprises at least one or more bypass valves by which the fluid communication of at least one pumping assembly with the patient interface can be at least partially restricted.

In one embodiment, the pump comprises at least one or more bypass valves by which the fluid communication of at least one pumping assembly with the patient interface can be at least partially restricted to change said pump from acting as a double acting pump to acting as a single acting pump.

In one embodiment, the at least one or more bypass valves are controlled or controllable by the controller.

In one embodiment, the at least one or more bypass valve can be actuated to vent compressed gas from at least one of the pump assemblies to atmosphere.

In another aspect, the invention may be said to consist in a method of controlling a resuscitator device, the method comprising the steps of

· receiving a tidal volume signal indicative of the tidal volume of gas required to be delivered to a patient; and

• determining the number and/or length of strokes and/or proportion of

strokes of the piston required to provide the required tidal volume to the patient.

In one embodiment, the method comprises the steps of:

• controlling the linear motor to move the piston for the required distance and/or determined number of strokes to provide a required tidal volume to the patient.

In one embodiment, the method comprises the steps of:

· stopping movement of the linear motor during an exhalation period of the patient.

In one embodiment, the method comprises the steps of: • controlling the linear motor to move the piston in an opposite direction to the direction the piston moved during the inhalation stroke.

In one embodiment, the method comprises the steps of:

• receiving a distance signal from a distance transducer; and

· determining a velocity signal indicative of the speed of movement of the linear motor and hence piston.

In one embodiment, the method comprises the steps of:

• receiving a pressure signal indicative of the pressure in the patient interface; and

· controlling movement of the linear motor to control movement of the piston to keep a minimum pressure in the patient interface above a predetermined threshold.

In one embodiment, the method comprises the steps of:

• determining a maximum piston stroke length limit corresponding to

maximum tidal volume to be delivered;

· controlling the motor to accelerate the piston to create an initial pressure in the patient interface; and

• receiving a pressure signal from a pressure transducer indicative of the

pressure in the patient interface.

In one embodiment, the method comprises the steps of:

· comparing the received pressure signal over time to determine whether the pressure reduces in the patient interface.

In one embodiment, the method comprises the steps of:

• timing the period over which the initial pressure is sustained in the patient interface.

In one embodiment, the method comprises the steps of:

· determining the rate of change of pressure in the patient interface over time.

In one embodiment, the method comprises the steps of:

• comparing the rate of change of pressure in the patient interface to

predetermined thresholds.

In one embodiment, the method comprises the steps of:

• determining one or more selected from the incremental pressure increase and the predetermined pressure and/or a predetermined volume flow rate depending on the result of the comparison of the rate of change of pressure to the predetermined thresholds.

In one embodiment, the method comprises the steps of:

• detecting whether the initial pressure or subsequent incremental pressures of the gas in the patient interface are released by inflation of the patients lungs within a predetermined period, and

• if the initially generated pressure of the gas in the patient interface has been released, controlling the motor to move the piston to sustain a delivery of gas at one or more selected from a predetermined pressure, a

predetermined tidal volume and a predetermined volume flow rate, until the pressure of the gas in the patient interface rises to a predetermined threshold, after which the piston is stopped.

In one embodiment, the method comprises the steps of:

• determining the rate of release of pressure in the patient interface over time; • comparing the rate of release of pressure in the patient interface with predetermined thresholds.

In one embodiment, the method comprises the steps of:

• controlling the motor to move the piston to sustain a delivery of gas at one or more selected from a predetermined pressure, a predetermined tidal volume and a predetermined volume flow rate in accordance with the comparison of the of the rate of release of pressure in the patient interface with predetermined thresholds.

In one embodiment, the method comprises the steps of:

· controlling the motor to move the piston to sustain a delivery of gas at one or more selected from a predetermined pressure, a predetermined tidal volume and a predetermined volume flow rate in accordance with the maximum pressure exerted before the pressure was released. In one embodiment, the method comprises the steps of:

In one embodiment, the pressure created by the piston is controlled by controlling one or more selected from the voltage and the current to the motor.

In one embodiment, the motor is a linear motor.

In one embodiment, the motor is a linear servomotor.

In one embodiment, control of the motor is by feedback loop control.

In one embodiment, control of the motor is by feedback loop control based on feedback received from a pressure transducer.

Alternatively, in one embodiment, control of the motor is by open loop control.

In one embodiment, the method comprises the steps of:

In one embodiment, the patient details are input by an operator and are one or more selected from the patient's age, weight and length.

In one embodiment, the method comprises the steps of:

• interrogating a data store using the received patient details In one embodiment, the method comprises the steps of:

• receiving an initial predetermined tidal volume signal indicative of an initial predetermine tidal volume to be delivered to the patient from a data store as a result of the interrogation.

In one embodiment, the method comprises the steps of:

• receiving a maximum best practice pressure signal indicative of a maximum best practice pressure from a data store as a result of the interrogation.

In one embodiment, the method comprises the steps of:

• receiving a best practice tidal volume signal indicative of a best practice tidal volume from a data store as a result of the interrogation.

In one embodiment, the method comprises the steps of:

• setting a maximum best practice pressure in the patient interface from the maximum best practice pressure signal.

In one embodiment, the method comprises the steps of:

· receiving a tidal volume increment signal from a data store as a result of the interrogation.

In one embodiment, the method comprises the steps of:

• receiving an initial predetermined tidal volume setting from a data store as a result of the interrogation..

In one embodiment, the method comprises the steps of:

• receiving a patient pressure signal indicative of one or more selected from the pressure in the patient interface and the pressure in the patient airways.

In one embodiment, the method comprises the steps of:

• controlling movement of the linear motor to move the piston to deliver a subsequent tidal volume determined from the initial tidal volume signal and the tidal volume increment signal.

In one embodiment, the method comprises the steps of:

· generating an alert signal if the comparison indicates that the patient

pressure signal is equal or exceeds the maximum best practice pressure signal.

In one embodiment, the method comprises the steps of: • comparing the best practice tidal volume to the subsequent tidal volume. In one embodiment, the method comprises the steps of:

In one embodiment, the method comprises the steps of:

In one embodiment, the method comprises delivering a predetermined number of inspiratory cycles at the manual pressure, and thereafter starts delivering subsequent tidal volumes at the maximum best practice pressure.

In one embodiment, the method comprises the steps of:

· controlling movement of the motor to move the piston to deliver a tidal volume to a patient at a constant target pressure.

In one embodiment, the method comprises the steps of:

· delivering a subsequent tidal volume to a patient during a subsequent

respiratory cycle;

• determining the airway pressure difference between the initial airway

pressure and the subsequent airway pressure.

In one embodiment, the method comprises the steps of:

• receiving a target pressure signal indicative of the target pressure.

In one embodiment, the method comprises the steps of:

• interrogating a data store for a target pressure.

In one embodiment, the method comprises the steps of:

• transmitting one or more selected from o the initial airway pressure

o the subsequent airway pressure

o the airway pressure difference.

In one embodiment, the method comprises the steps of:

· controlling movement of the motor to control movement of the piston to stop delivery of further gas to the patient if patient airway pressure exceeds a maximum pressure threshold.

In one embodiment, the method comprises the steps of:

• retrieving an initial predetermined tidal volume setting from a data store. In one embodiment, the method comprises the steps of:

• receiving an initial pressure signal indicative of one or more selected from the pressure in the patient interface and the pressure in the patient airways; and

In one embodiment, the method comprises the steps of:

• comparing the initial pressure signal and the subsequent pressure signal. In one embodiment, the step of comparing the initial pressure signal and the subsequent pressure signal includes the step of determining the rate of change of pressure.

In one embodiment, the method comprises the steps of:

• determining a tidal volume increment in accordance with the comparison of the initial pressure signal and the subsequent pressure signal.

In one embodiment, the method comprises the steps of:

• interrogating a data store for a tidal volume corresponding to the

comparison of the initial pressure signal and the subsequent pressure signal.

In one embodiment, the step of determining the tidal volume increment includes the step of retrieving a tidal volume increment from a data store

In one embodiment, the method comprises the steps of: • determining a subsequent tidal volume to be delivered to a patient.

In one embodiment, the method comprises the steps of:

· controlling movement of the motor to move the piston to deliver a

subsequent tidal volume.

In one embodiment, the method comprises the steps of:

• controlling movement of the motor to move the piston to move at a

relatively high respiratory rate and a relatively low tidal volume; · controlling the movement of the linear motor to incrementally increase the tidal volume delivered via the patient interface.

In one embodiment, the method comprises the steps of:

• receiving a pressure signal indicative of the pressure in the patient interface. In one embodiment, the method comprises the steps of:

· controlling movement of the motor to decelerate or stop the piston when the pressure signal reaches a predetermined threshold pressure.

In one embodiment, the method comprises the steps of:

predetermined threshold pressure was reached.

In one embodiment, the method comprises the steps of:

• transmitting an alert signal in order to alert an operator that a

predetermined threshold pressure has been reached.

In one embodiment, the method comprises the steps of:

· providing a manual override option to an operator, whereby one or more selected from the tidal volume, the inspiratory pressure being delivered by the pump and the respiratory rate is manually settable..

In one embodiment, the method comprises the steps of:

· receiving a best practice initial respiratory rate signal indicative of a best practice initial respiratory rate from a data store.

In one embodiment, the method comprises the steps of: • receiving a best practice initial respiratory rate signal indicative of a best practice initial respiratory rate from a data store.

In one embodiment, the method comprises the steps of:

• interrogating a data store for a best practice ramping pressure signal.

In one embodiment, the method comprises the steps of:

• comparing the patient pressure to a threshold ramping pressure.

In one embodiment, the method comprises the steps of:

In one embodiment, the step of retrieving the respiratory rate increment signal is rried out by interrogating a data store using one or more selected from:

• the rate of change of pressure,

• the pressure difference

In one embodiment, the method comprises the steps of:

• determining a subsequent respiratory rate.

In one embodiment, the method comprises the steps of:

• determining a subsequent respiratory rate using the respiratory rate

increment signal.

In one embodiment, the step of determining the subsequent respiratory rate is by btracting the respiratory rate increment from the last respiratory rate.

In one embodiment, the method comprises the steps of:

• controlling the motor to move the piston to move at the subsequent

respiratory rate

In one embodiment, the method comprises the steps of:

• receiving a predetermined ramping pressure signal from a data store.

In one embodiment, the method comprises the steps of: • receiving a pressure signal from a pressure sensor in one or more selected from the patient interface and the patient's airway.

In one embodiment, the method comprises the steps of:

• controlling movement of the motor to move the piston to deliver an initial tidal volume during an inspiratory phase of a patient.

In one embodiment, the method comprises the steps of:

· comparing the received pressure signal from the pressure sensor to the ramping pressure signal.

In one embodiment, the method comprises the steps of:

• timing the expiratory cycle as a time signal.

In one embodiment, the method comprises the steps of:

· retrieving an expiratory cycle time threshold signal indicative of the

maximum time limit of the expiratory cycle of a patient.

In one embodiment, the method comprises the steps of:

• determining an expiratory cycle time threshold signal indicative of the

maximum time limit of the expiratory cycle of a patient.

In one embodiment, the method comprises the steps of:

• comparing the time of the expiratory cycle to the expiratory cycle time

threshold signal.

In one embodiment, the method comprises the steps of:

· the voltage across at least part of the linear motor;

• the current through at least part of the linear motor;

• the power being used by the linear motor. In one embodiment, the instructions are configured for directing the controller to control the pressure generated by the piston by controlling one or more selected from

• the power of the linear motor,

• the voltage provided to at least a part of the linear motor, and

· the current supplied to at least a part of the linear motor.

• the power of the linear motor,

· the voltage provided to at least a part of the linear motor, and

• the current supplied to at least a part of the linear motor.

In one embodiment, the method comprises the steps of:

• receiving a patient pressure signal indicative of the pressure of the gas at or about one or more selected from the patient interface and the patient's airways.

In one embodiment, the method comprises the steps of:

• receiving a maximum pressure signal from a data store.

In one embodiment, the received maximum pressure signal is received in response to an interrogation of the data store for a maximum pressure signal corresponding to input patients details.

In one embodiment, the method comprises the steps of:

• receiving an inlet pressure signal indicative of the pressure of the gas at or about the inlet. In one embodiment, the method comprises the steps of:

• determining a compensated tidal volume to be provided at ambient pressure to a patient;

• controlling movement of the motor to accelerate the piston to provide a compensated tidal volume to one or more selected from a patients airways and the patient interface.

In one embodiment, the step of determining a compensated tidal volume comprises the step of interrogating a data store for a compensation factor associated with the inlet pressure signal.

• calculating a compensation factor from a set of associated parameters; and

• calculating a compensated tidal volume from a set of associated parameters. In one embodiment, the step of determining a compensated tidal volume comprises the step of interrogating a data store for one or more selected from

• a compensation factor associated with the inlet pressure signal; and

• a compensated tidal volume.

· a compensation factor associated with the inlet pressure signal; and

• a compensated tidal volume.

In one embodiment, the associated parameters comprise one or more of

• inlet pressure,

• best practice tidal volume to be delivered,

· ambient pressure,

• ambient temperature,

• temperature at the inlet;

• flow velocity at the inlet,

• or the like.

In one embodiment, the patient interface comprises a flow sensor.

In one embodiment, the controller is configured for receiving the flow signal.

In one embodiment, the method comprises the steps of:

· receiving a flow signal from a flow transducer.

In one embodiment, the method comprises the steps of:

• integrating the flow sensor readings over time to determine a volume.

In one embodiment, the method comprises the steps of: • integrating the flow sensor readings from the start of the inspiration cycle of a patient to the end of the inspiration cycle of a patient to determine a patient tidal volume.

In one embodiment, the method comprises the steps of:

· determining the volume of gas delivered by the piston to the patient

interface as a pumped volume.

In one embodiment, the method comprises the steps of:

• comparing the pumped volume to the patient tidal volume.

In one embodiment, the method comprises the steps of:

• controlling the motor to control movement of the piston to increase or

decrease the pumped tidal volume in accordance with the determination of the difference between the pumped volume and the patient tidal volume.

In one embodiment, the method comprises the steps of:

· receiving an initial patient pressure signal indicative of the pressure in one or more of the patient interface and the patient's airways during an expiratory cycle of the patient.

In one embodiment, the method comprises the steps of:

• comparing the initial patient pressure signal and the subsequent patient pressure signal.

In one embodiment, the method comprises the steps of:

• determining if the subsequent patient pressure signal has dropped below the initial patient pressure signal by a predetermined amount.

In one embodiment, the method comprises the steps of:

In one embodiment, the method comprises the steps of: • receiving an initial patient flow rate signal indicative of the gas flow rate in one or more of the patient interface and the patient's airways during an expiratory cycle of the patient.

In one embodiment, the method comprises the steps of:

• comparing the initial patient flow rate signal and the subsequent patient flow rate signal.

In one embodiment, the method comprises the steps of:

• retrieving the predetermined amount from a data store.

In one embodiment, the method comprises the steps of:

· controlling movement of the motor to move the piston based on the

determination of the rate of change of pressure over time.

In one embodiment, the method comprises the steps of:

• determining the length of time that the expiratory cycle has been ongoing. In one embodiment, the method comprises the steps of:

· comparing the time that the expiratory cycle has been ongoing and the predetermined maximum expiratory time.

In one embodiment, the method comprises the steps of:

• actuating movement of the motor to move the piston to pump gas to the patient to start an inspiratory cycle of the patient if the expiratory cycle is equal to or exceeds predetermined maximum expiratory time. In one embodiment, the patient interface comprises a gas level sensor.

In one embodiment, the method comprises the steps of:

· receiving a gas level signal from a gas level sensor.

In one embodiment, the method comprises the steps of:

• receiving a predetermined best practice gas level range from a data store. In one embodiment, the method comprises the steps of:

• interrogating a data store based on input patient's details for one or more selected from a best practice gas level range and a best practice gas level.

In one embodiment, the method comprises the steps of:

• transmitting an alert signal if the received gas level signal does not

substantially correlate with the best practice gas level signal.

In one embodiment, the gas level sensor is one or more selected from a :

• carbon dioxide sensor;

• carbon monoxide sensor;

• nitrogen sensor;

• or the like

In a further aspect the present invention consists in a resuscitator as herein before described and as herein described with reference to the accompanying drawings.

In a further aspect the present invention consists in a resuscitator as herein described with reference to the accompanying drawings.

In a further aspect the present invention consists in a pump for a resuscitator as herein before described and as herein described with reference to the accompanying drawings.

In a further aspect the present invention consists in a pump for a resuscitator as herein described with reference to the accompanying drawings.

According to another aspect the present invention comprises a method of controlling a resuscitator device, to be carried out by a controller, the method comprising the steps of

a. receiving one or more patient details; b. receiving a best practice tidal volume signal associated with a best practice tidal volume to be delivered to a patient associated with the said one or more patient details;

c. controlling the motor to move the piston to deliver an initial tidal volume during an initial respiratory cycle that is smaller than the best practice tidal volume; d. controlling the motor to move the piston to deliver an incrementally increased tidal volume in subsequent respiratory cycles, until the delivered tidal volume in a respiratory cycle is equal to the best practice tidal volume.

According to another aspect, wherein the method comprises the step of:

a. receiving an airway pressure signal indicative of the patient airway pressure.

According to another aspect, wherein the method comprises the step of:

a. receiving a best practice maximum pressure signal associated with a best practice maximum pressure for a respiratory cycle to be delivered to a patient associated with the patient details.

According to another aspect, wherein the method comprises the step of:

a. comparing the patient airway pressure to the best practice maximum pressure.

According to another aspect, wherein step of controlling the motor to move the piston to deliver an incrementally increased tidal volume is carried out only if the last delivered tidal volume is lower than the best practice tidal volume and the patient pressure does not exceed the best practice maximum pressure.

According to another aspect, wherein the step of step of controlling the motor to move the piston to deliver incrementally increased subsequent tidal volume includes the steps of:

a. comparing the last delivered tidal volume to the best practice tidal volume; and

b. controlling movement of the motor and the piston to stop further delivery of gas to the patient during a respiratory cycle if the delivered tidal volume exceeds a threshold tidal volume associated with the best practice tidal volume.

According to another aspect, wherein the step of receiving an airway pressure signal indicative of the patient airway pressure includes the step of determining the patient pressure in one or more selected from a patient's airway and a patient interface.

According to another aspect, wherein the step of determining the patient pressure comprises one or more of the steps selected from :

a. receiving said airway pressure signal from a pressure transducer in a patient interface; and b. determining the pressure being applied by the piston from one or more selected from

i. the power across the motor;

ii. the voltage across the motor; and

iii. the current across the motor.

According to another aspect, wherein the method comprises the steps of:

a. comparing the patient airway pressure to a threshold maximum pressure associated with the best practice maximum pressure; and

b. controlling movement of motor and the piston to stop further delivery of gas to the patient during a respiratory cycle if the patient airway pressure exceeds the threshold maximum pressure associated with the best practice maximum pressure.

According to another aspect, wherein the method comprises the step of:

a. controlling movement of the motor and the piston to control the respiratory rate.

According to another aspect, wherein the method comprises the step of:

a. receiving a best practice respiratory rate signal associated with a best practice respiratory rate for the patient.

According to another aspect, wherein the method comprises the step of:

a. controlling movement of the motor and the piston to initially deliver gas to the patent at the best practice respiratory rate.

According to another aspect, wherein the method comprises the step of:

a. controlling movement of motor and the piston to control the ratio of the period of the inspiratory cycle to the period of the expiratory cycle (hereinafter " the I: E ratio") in a respiratory cycle.

According to another aspect, wherein the method comprises the step of:

a. receiving a best practice I: E ratio signal indicative of the best practice I: E ratio for said patient.

According to another aspect, wherein the method comprises the step of:

a. controlling movement of the motor and the piston to initially deliver a respiratory cycle to the patent at the best practice I: E ratio for said patient.

According to another aspect, wherein the method comprises the step of:

a. receiving one or more selected from

i. a carbon dioxide signal indicative of the levels of carbon dioxide in the patient's airways;

ii. an oxygen signal indicative of the levels of oxygen in the patient's bloodstream;

iii. a temperature signal indicative of the temperature of gas in the patients airways; and iv. a flow signal indicative of one or more selected from

1. the speed of gas flow through the patient interface; and

2. the direction of gas flow through the patient interface.

According to another aspect, wherein the method comprises the step of:

a. interrogating a data store, in the event of the delivered tidal volume being lower than the best practice tidal volume, to retrieve said one or more selected from

i. a tidal volume increment signal, indicative of an incremental increase in tidal volume to be delivered in a subsequent respiratory cycle,

ii. a tidal volume signal indicative of the increased tidal volume to be delivered in a subsequent respiratory cycle,

iii. a respiratory rate signal indicative of the respiratory rate at which subsequent respiratory cycles are to be delivered,

iv. a respiratory rate increment signal indicative of the increment by which the current respiratory rate is to be changed, and

v. a best practice I: E ratio for said patient.

According to another aspect, wherein the method comprises the step of:

a. receiving, in the event of the airway pressure being lower than the best practice maximum pressure, one or more selected from :

i. a tidal volume increment signal, indicative of an incremental increase in tidal volume to be delivered in a subsequent respiratory cycle;

ii. a tidal volume signal indicative of the increased tidal volume to be delivered in a subsequent respiratory cycle;

iii. a respiratory rate signal indicative of the respiratory rate at which subsequent respiratory cycles are to be delivered; and

iv. a respiratory rate increment signal indicative of the increment by which the current respiratory rate is to be changed.

According to another aspect, wherein the step of controlling the motor to move the piston to deliver an incrementally increased tidal volume, includes the step of delivering said incrementally increased tidal volume at a respiratory rate that is incrementally increased or decreased.

According to another aspect, wherein the method comprises the step of:

a. determining the respiratory rate at which the incrementally increased tidal volume is to be delivered using one or more selected from

i. the respiratory rate signal, and

ii. the respiratory rate increment signal.

According to another aspect, wherein the method comprises the step of:

a. determining an incrementally increased tidal volume to be delivered using one or more selected from i. the tidal volume increment signal, and

ii. the tidal volume signal.

According to another aspect, wherein the method comprises the step of:

a. controlling the motor to move the piston to deliver an incrementally increased tidal volume to said patient that is incrementally larger than the previous delivered tidal volume an amount associated with the tidal volume increment signal received from the data store.

According to another aspect, wherein the method comprises the step of:

a. generating an alert signal in the event of the airway pressure being greater than a threshold maximum pressure associated with the best practice maximum pressure.

According to another aspect, wherein the alert signal includes one or more steps selected from:

a. presenting an operator with an option for allowing a manual override of one or more selected from

i. the maximum best practice pressure,

ii. the tidal volume to be delivered to the patient, and

iii. the respiratory rate at which gas is to be delivered to the patient;

b. displaying a message on a monitor,

c. actuating another control process, and

d. generating an audio or visual alarm.

According to another aspect, wherein the step of controlling movement of motor and hence the piston to stop further delivery of gas to the patients comprises one or more selected from the steps of:

a. stopping movement of the motor to stop movement of the piston; and b. controlling movement of the motor to prevent movement of the piston in a direction to deliver gas to said patient.

According to another aspect, wherein the method comprises the step of:

a. controlling the motor to move the piston to deliver a reduced subsequent tidal volume during a subsequent respiratory cycle in the event that the patent airway pressure exceeds the threshold maximum pressure.

According to another aspect, wherein the method comprises the step of:

a. moving the motor to move the piston at a reduced respiratory rate in the event that the patent airway pressure exceeds the threshold maximum pressure.

According to another aspect, wherein the method comprises the steps of:

a. interrogating a data store in the event that the threshold maximum pressure is exceeded by the patients airway pressure; and b. receiving from a data store as a result of the interrogation, one or more selected from

i. a tidal volume increment signal, indicative of an incremental decrease in tidal volume to be delivered in a subsequent respiratory cycle;

ii. a tidal volume signal indicative of the decreased tidal volume to be delivered in a subsequent respiratory cycle;

According to another aspect, wherein the reduced subsequent tidal volume is determined from the tidal volume delivered during the last inspiratory cycle and the tidal volume increment signal.

According to another aspect, wherein the step of interrogating the data store comprises the step of transmitting treatment details to a data store.

According to another aspect, wherein step of interrogating the data store comprises the step of transmitting treatment details for indexing against one or more selected from a. an index,

b. patient data,

c. an algorithm,

d. a formula,

e. data tables or

f. instructions

According to another aspect, wherein the treatment details are any one or more selected from:

a. the levels of carbon monoxide in the patient's airways or bloodstream during any current or prior respiratory cycle;

b. the levels of carbon dioxide in the patient's airways or bloodstream during any current or prior respiratory cycle;

c. the levels of oxygen in the patient's airways or bloodstream during any current or prior respiratory cycle;

d. the received patient details;

e. the tidal volume delivered during any current or prior respiratory cycle. f. the patients airway pressure at any point during any current or prior respiratory cycle;

g. the difference between the patient airway pressure at the end of an initial respiratory cycle and the patient airway pressure at the end of a subsequent respiratory cycle; h. rate of change of pressure in the patient's airways from one respiratory cycle to the next for any current or prior respiratory cycle;

i. I: E ratio for any current or prior respiratory cycle;

j . respiratory rate for any current or prior respiratory cycle.

According to another aspect, wherein the input patient details relate to one or more selected from the patient's age, weight or length.

According to another aspect, wherein the method comprises the step of:

a. controlling movement of the motor to move the piston to deliver one or more subsequent inspiratory cycles at one or more selected from:

i. a manual override maximum pressure set by the operator;

ii. a manual override tidal volume set by the operator; and

iii. a manual override respiratory rate set by the operator.

According to another aspect, wherein the method comprises the steps of:

a. controlling movement of the motor and piston to deliver a predetermined number of inspiratory cycles at one or more selected from

i. the manual override maximum pressure,

ii. manual override tidal volume, and

iii. manual override respiratory rate set by the operator.

b. controlling movement of the motor and piston to deliver subsequent tidal volumes at the values they were at prior to the manual override.

According to another aspect the present invention comprises a resuscitation device for delivering gas to a patient in respiratory cycles comprising alternating respiratory and expiratory cycles, said resuscitation device comprising :

a. a rigid cylinder including at least one gas inlet and at least one gas outlet, b. a piston movable in said cylinder in a reciprocating manner in at least a first stroke direction and a second stroke direction, and

c. at least one valve assembly configured for allowing gas to be drawn into said cylinder through said at least one gas inlet when the piston is moving in a first stroke direction in said cylinder, and for allowing gas to be displaced through said at least one gas outlet when the piston is moving in a second stroke direction;

d. an accurate positionally controllable motor operatively connected to said piston to move said piston in said cylinder;

e. a controller configured for controlling the motor to control the position of the piston in the cylinder,

i. the controller comprising digital storage media for storing digital instructions, ii. wherein the instructions are configured for carrying out the method according to any one of claims 1 to 35. According to another aspect the present invention comprises a method of controlling a resuscitator device, to be carried out by a controller, the method comprising the steps of

a. receiving an initial tidal volume signal indicative of a tidal volume to be initially delivered to a patient ;

b. receiving a threshold maximum pressure signal indicative of a threshold maximum pressure allowable in a patients airways during an inspiration cycle;

c. controlling movement of the motor to move the piston to deliver an initial tidal volume corresponding to the predetermined initial tidal volume signal;

d. receiving an airway pressure signal indicative of the patient airway pressure,

e. comparing the patient airway pressure to the maximum pressure; and f. delivering an increased subsequent tidal volume if the patient airway pressure does not exceed a threshold maximum pressure associated with the maximum pressure.

According to another aspect, wherein the method comprises the step of:

a. receiving an initial respiratory rate signal indicative of the respiratory rate at which the respiratory cycle is to be initially delivered to a patient.

According to another aspect, wherein the method comprises the step of:

a. receiving and/or determining patient feedback signals from transducers relating to the state of the patient.

According to another aspect, wherein the patient feedback signals are one or more selected from:

a. a carbon monoxide signal indicative of the levels of carbon monoxide in the patient's airways or bloodstream during any current or prior respiratory cycle;

b. a carbon dioxide signal indicative of the levels of carbon dioxide in the patient's airways or bloodstream during any current or prior respiratory cycle;

c. an oxygen signal indicative of the levels of oxygen in the patient's airways or bloodstream during any current or prior respiratory cycle;

d. a tidal volume feedback signal indicative of the tidal volume delivered during any current or prior respiratory cycle.

e. a patient airway pressure signal indicative of the patients airway pressure at any point during any current or prior respiratory cycle;

f. a patient airway pressure difference signal indicative of the difference between the patient airway pressure at the end of an initial respiratory cycle and the patient airway pressure at the end of a subsequent respiratory cycle;

g. a rate of change of pressure signal indicative of the rate of change of pressure in the patient's airways from one respiratory cycle to the next for any current or prior respiratory cycle; h. an I: E ratio signal indicative of the I: E ratio for any current or prior respiratory cycle of the patient;

i. a respiratory rate signal indicative of the respiratory rate for any current or prior respiratory cycle.

According to another aspect, wherein the method comprises the step of a. determining a pressure difference signal indicative of the pressure difference in the patients airways from one inspiratory cycle to the next.

According to another aspect, wherein the pressure difference signal is indicative of the pressure difference in the patient's airways from the end of the last inspiratory cycle to the end of the current inspiratory cycle.

According to another aspect, wherein the method comprises the step of:

a. interrogating a data store using one or more selected from the pressure difference signal, the pressure difference, and the patient feedback signals to retrieve one or more selected from

i. a subsequent tidal volume signal indicative of a subsequent tidal volume to be delivered to the patient in a subsequent respiratory cycle;

ii. a subsequent respiratory rate signal indicative of a respiratory rate at which a subsequent respiratory cycle is to be delivered to a patient;

iii. a subsequent I: E ratio indicative of the I: E ratio at which a subsequent respiratory cycle is to be delivered to a patient;

iv. a subsequent maximum pressure signal indicative of the maximum pressure at which a subsequent inspiratory cycle is to be delivered to a patient.

According to another aspect, wherein the step of delivering an increased subsequent tidal volume is delivered at one or more selected from

i. a subsequent tidal volume according to the received subsequent tidal volume signal;

ii. a subsequent respiratory rate according to the received subsequent respiratory rate signal;

iii. a subsequent I: E ratio according to the received subsequent I: E ratio signal; and

iv. a subsequent maximum pressure according to the received subsequent pressure signal.

According to another aspect, wherein the step of interrogating the data store comprises the step of transmitting treatment details for indexing against one or more selected from:

a. an index.

b. patient data,

c. an algorithm, d. a formula,

e. data tables or

f. instructions

According to another aspect, wherein the predetermined initial tidal volume signal is a default signal.

According to another aspect, wherein the method comprises the step of:

a. generating an alert signal in the event of the airway pressure being greater than the threshold maximum pressure.

According to another aspect, wherein the alert signal includes one or more selected from:

. the maximum best practice pressure,

i. the tidal volume to be delivered to the patient,

iii. the I: E ratio of the tidal volume to be delivered to the patient; and v. the respiratory rate at which gas is to be delivered to the patient; b. displaying a message on a monitor,

c. actuating another control process, and

d. generating an audio or visual alarm.

According to another aspect, wherein the step of controlling movement of motor and hence the piston to stop further delivery of gas to the patients comprises one or more selected from the steps of

a. stopping movement of the motor to stop movement of the piston; and b. controlling movement of the motor to move the piston in said first stroke direction.

According to another aspect, wherein the method comprises the step of:

a. moving the motor to move the piston at a reduced respiratory rate in the event that the patient airway pressure exceeds the threshold maximum pressure.

According to another aspect, wherein the method comprises the step of:

a. controlling movement of the motor to move the piston to deliver one or more subsequent respiratory cycles at one or more selected from:

. a manual override maximum pressure set by the operator;

i. a manual override tidal volume set by the operator;

ii. a manual override I: E ratio set by the operator; and iv. a manual override respiratory rate set by the operator;

According to another aspect, wherein the method comprises the step of:

i. the manual override maximum pressure,

ii. manual override tidal volume, and

iii. manual override respiratory rate set by the operator,

According to another aspect, wherein the method comprises one or more steps selected from:

a. determining the subsequent tidal volume to be delivered to the patient from the subsequent tidal volume signal;

b. determining the subsequent respiratory rate to be delivered to the patient from the subsequent respiratory rate signal;

c. determining the subsequent I: E ratio of the subsequent respiratory cycle to be delivered to the patient from the subsequent I: E ratio signal; and

d. determining the subsequent maximum pressure of the subsequent inspiratory cycle to be delivered to the patient from the subsequent maximum pressure signal.

According to another aspect, wherein the method comprises the step of

a. setting the subsequent maximum pressure as the threshold maximum pressure that is not to be exceeded during delivery of the increased subsequent tidal volume.

According to another aspect, wherein the step of delivering an increased

subsequent tidal volume includes the steps of delivering the increased subsequent tidal volume at one or more selected from

a. the determined subsequent respiratory rate;

b. the determined subsequent I: E ratio.

According to another aspect the present invention comprises a resuscitation device for delivering gas to a patient in respiratory cycles comprising alternating inspiratory and expiratory cycles, said resuscitation device comprising :

i. the controller being configured for receiving direction from instructions;

wherein the instructions are configured for directing the controller to carry out the steps of the method of any one of claims 37 to 56.

This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known

equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

As used herein the term "and/or" means "and" or "or", or both.

As used herein "(s)" following a noun means the plural and/or singular forms of the noun.

The term "comprising" as used in this specification means "consisting at least in part of". When interpreting statements in this specification which include that term, the features, prefaced by that term in each statement, all need to be present but other features can also be present. Related terms such as "comprise" and "comprised" are to be interpreted in the same manner.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred form of the present invention will now be described with reference to the accompanying drawings in which,

Figure 1 is a schematic view of a resuscitator and is shown to describe it being in the inhalation phase,

Figure 2 is a schematic view of a resuscitator and is shown to describe it in the exhalation phase,

Figure 3 shows the resuscitator in a CPAP mode wherein a supplementary gas is supplied to the resuscitator,

Figure 4 is a schematic view of a variation of the resuscitator shown in Figures 1-3, also in a CPAP mode and wherein a flexible conduit extends between parts of the resuscitator to provide to some extent, independence of movement of the face mask relative some of the other components of the resuscitator, Figure 5 is a schematic view of a variation of the resuscitator shown in an exhalation phase with reference to Figures 1-4,

Figure 6 is a schematic view of the resuscitator of Figure 5 shown in operation, moving in an inhalation phase,

Figure 7 is a schematic view of the resuscitator of Figure 5 shown in an inhalation phase,

Figure 8 shows the resuscitator of Figure 5 in an inhalation mode and wherein an oxygen supply is provided to allow the operation of the resuscitator in a CPAP mode,

Figure 9 illustrates the resuscitator of Figure 5, wherein a flexible conduit is provided intermediate of certain parts of the resuscitator to provide, to a certain extent, independence of movement of the face mask relative to some of the other components of the resuscitator,

Figure 10 is a sectional view of the face mask shown to include a flow and tidal volume sensor wherein the gas flow is shown in an inhalation direction, and

Figure 11 is a variation to that shown in Figure 10 wherein it is shown in an exhalation condition.

Figure 12 shows a schematic view of inserted single acting resuscitator pump, with a separate CPAP blower and CPAP gas bypass conduit;

Figure 13 shows a schematic view of a double acting resuscitator;

Figure 14 is a flow chart showing control of the maximum tidal volume to be delivered to a patent;

Figure 15 is a flow chart showing how acceleration of a piston may be determined;

Figure 16 is a flow chart showing how the maximum pressure in the patient interface may be controlled;

Figure 17 is a flow chart showing how the rate of change of pressure may be monitored and used to control the resuscitator;

Figure 18 is a piston displacement v time graph of an inspiratory cycle;

Figure 19 shows a pressure-time graph of an inspiratory cycle;

Figure 20 is a flow chart showing one embodiment of how pressure created by the piston may be increased in increments, while being maintained under a maximum tidal volume;

Figure 21 is a pressure v time graph of an inspiratory cycle;

Figure 22 is a flow chart showing how delivery of an initial tidal volume may be increased in increments while maintaining pressure under a best practice threshold pressure;

Figure 23 is a flow chart showing a control sequence to prevent ramping;

Figure 24 is a flow chart showing a control sequence for compensating for pre- pressurisation of gas at CPAP pressures; and Figure 25 is a flow chart showing a control sequence for detecting and

compensation for leakage;

Figure 26 is a graph of tidal volume versus time and airway pressure versus time showing a series of typical respiratory cycles;

Figure 27 is a graph of tidal volume versus time and airway pressure versus time showing a series of respiratory cycles in which the patient's airways are blocked;

Figure 28 is a graph of tidal volume versus time and airway pressure versus time showing a series of respiratory cycles where a minimum CPAP pressure is maintained;

Figure 29 is a graph of tidal volume versus time and airway pressure versus time showing how ramping occurs in a series of respiratory cycles;

Figure 30 is a graph of tidal volume versus time and airway pressure versus time illustrating a time period after an initial respiratory cycle after which triggering mode can become actuated;

Figure 31 is a graph of tidal volume versus time and airway pressure versus time illustrating best practice delivery mode;

Figure 32 is a graph of total volume versus time and airway pressure versus time illustrating auto mode;

Figure 33 is a flow chart showing an embodiment of a control sequence for the best practice delivery mode;

Figure 34 is a flow chart showing an embodiment of a control sequence for auto mode; and

Figure 35 is a graph of tidal volume versus time and airway pressure versus time showing how an operator can override a control process. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to Figure 1, there is shown a resuscitator 1. The resuscitator 1 consists of a resuscitator body 2. It may also include associated hardware such as a controller 3, a display 4 and power supply 5 connected to each other and/or the resuscitator body 2.

The resuscitator body 2 consists of a pump unit 6, a flow control unit 7 and preferably a patient interface 8.

Broadly speaking the pump unit 6 includes a pump that will deliver air to the flow control unit 7. The flow control unit 7 will control the flow of gas between the patient interface and the flow control unit 7 in conjunction with or without the pump unit 6 depending on the status of operation of the resuscitator 1.

In the most preferred form the pump unit 6 and flow control unit 7 are part of the same body as for example shown in Figure 1. A conduit 9 extending between the flow control unit 7 and the patient interface 8 facilitates the flow of gas between the interface and the flow control unit 7.

In the examples shown in the accompanying drawings, the interface is preferably a face mask. However, alternatively, the interface may be an endotracheal tube or naso- tube that extends partly into the patient's airway.

The pump unit 6 consists of a piston 10 that locates in a cylinder 11 to displace gas through an outlet 12 of the cylinder and to the flow control unit 7. The piston and cylinder are a complementary shape and make sure that a sufficiently tight seal exists between the piston and cylinder for the purposes of positively displacing gas through the outlet 12.

The cylinder 11 may be cylindrical in cross-section or may be any other shape in cross-section.

The piston is actuated via its connection rod 14, by a motor 13. In the most preferred form the motor is an actuator preferably a linear motor. In an alternative form the actuator may be a servomotor, stepper motor or similar device.

Preferably the motor comprises a feedback mechanism operable, in conjunction with a processing device, to allow accurate control of the piston displacement. Preferably the processing device is a microcontroller, digital signal processor or similar device capable of receiving a signal indicative of displacement and making decisions based on stored or formulaic data. The feedback mechanism and processing device preferably act in a closed loop. That is, changes in sensor readings are measured by the processing device and the processing device outputs a signal to control movement of the motor based on that reading.

The feedback mechanism preferably comprises a device for transferring energy associated with piston movement or piston position into electrical energy for sensing by the processing device. Such devices include optical, capacitive or inductive sensors sensitive to the proximity between a moveable component of or on the motor and the sensor, a resistive sensor which typically has a resistive wiper arm, or may comprise other sensory methods such as measurement of the back electromotive force generated following energising of the motor.

Fine control of the motor displacement is a function of the resolution of the processing device and sensor used, and the commutation step resolution of the motor itself. However, a step-less motor may be used. In preferred embodiments, a Hall effect sensor is implemented to detect small changes in displacement of a ferrous component of the motor. The Hall sensor generates small voltages in response to a change in displacement that the processing device can sense and act on accordingly.

The connection rod 14 must be the reactor to operate in conjunction with the motor 13 for the purposes of displacing the piston. The connection rod 14 may be the reactor to operate in conjunction with the motor 13 for the purposes of displacing the piston 10 in the cylinder 11 in an oscillating or reciprocating manner. Alternatively the connection rod 14 may carry a reactor plate or surface in conjunction with the motor 13. In the figures, the connection rod 14 is acted upon directly by the motor 13. The reactor plate may also be incorporated as part of the piston to be integral therewith. No connection rod need then be provided.

Alternative mechanisms may be employed where such action is indirect via a linkage mechanism. Such linkage may include a rotor and crank and connection rod. It will be appreciated that regardless of which part of a linear motor the piston is attached to, it is the relative movement between the at least two parts that is used to create relative movement between the piston and the cylinder.

In the most preferred form the motor 13 is a linear motor or any other motor that has accurate and rapid positional control capabilities. The controller 3 via a connection 15 with the motor 13 will operate the motor in a manner so that the desired delivery or respiratory rate, flow rate, tidal volume and pressures are being delivered through the outlet opening 12.

The flow control unit 7 consists of an inlet that may coincide with or define the outlet 12 of the pump unit. The flow control unit includes an outlet 20 and a passage extending between the inlet and outlet. The passage allows the transmission of gas being displaced from the pump unit 6 to the outlet 20. The outlet 20, preferably via a conduit 9, allows the delivery of this gas to the patient interface 8.

Intermediate of the inlet and outlet of the flow control unit is a one-way valve 21. The one-way valve allows for gas to travel from the inlet towards the outlet via the passage but prevents flow of gas from the outlet to the inlet.

The valve 21 may be mounted in a fixed manner to the housing 22 of the flow control unit 7 or alternatively and as shown in Figure 1, may be mounted to a movable mount 23 to move the valve mount.

In the preferred form the movable mount 23 forms part of a voice coil actuator 24 that can displace the movable mount 23 between two positions. The first position is as shown in Figure 1 and the second position is as shown in Figure 2. This creates a valve referred to herein as the exhalation or exhaust valve. In Figure 1 the moveable mount 23 is located in a position so that at least on the outlet 20 side of the valve 21, no other opening to the passage of the flow control unit 7 is created. All gas that is displaced by the pump unit 6 is captured for flow towards the patient interface 8.

In the second position of the mount as shown in Figure 2, an opening 27 is created between part of the housing 22 of the flow control unit 7 and the moveable mount 23. In this position gas can escape from that part of the passage of the flow control unit 7 intermediate of the valve 21 and the flow control unit outlet 20. In this position of the moveable mount 23, gas that may be exhaled from the patient can travel through the opening 27 for example towards the surrounding atmosphere through opening 29. The opening 27 may be an annular opening that is created between a substantially disk shaped mount portion and a circular shaped seat 30 of the housing 22 of the flow control unit 7.

As a consequence of a pressure differential between the patient side and pump side of the one-way valve 21, the one-way valve 21 will assume a closed position as shown in Figure 2 during the exhalation operating phase of the resuscitator. This negative pressure differential may be established by one or more of a combination of the patient breathing out, the retraction of the piston in its cylinder away from the outlet 12 and the movement of the voice coil actuator 24 in a direction establishing the opening 27. In the most preferred form it is the voice coil actuator 24 that primarily establishes the open and closed condition between the opening 27 and that part of the passage of the flow control unit 7 between the flow control unit outlet 20 and the one-way valve 21.

However where a patient is breathing on their own and is able to create sufficient pressure, movement of the moveable mount 23 of the valve 21 to create the opening 27 may occur without assistance of the voice coil actuator. It will be appreciated that other actuators may be used. Actuators that move other components other than the valve 21 to create such an opening for exhaled gases to be discharged may be used.

In the exhalation operating phase of the resuscitator, the piston is withdrawn by the motor 13 preferably back to a predetermined start position. The piston retracts once it has travelled its full desired stroke during the inhalation operating phase and has delivered the required tidal volume or has timed out while holding the maximum airway pressure during the inhalation period. Control of the position or movement of the voice coil actuator 24 can occur by the controller 3 and is preferably synchronised with movement of the piston.

It is envisaged that the resuscitator 1 can operate in one or both of a Constant Positive Airway Pressure (CPAP) or a Positive End-Expiratory Pressure (PEEP) mode. In a CPAP mode, a constant minimum pressure is maintained throughout the entire breathing cycle of the patient.

In PEEP mode, a minimum pressure is maintained towards the end of the expiratory cycle of a patient, to ensure that sufficient pressure is maintained to ensure that the patient's lungs do not collapse.

It is generally accepted that providing CPAP ventilation is a better choice than PEEP ventilation, in case other anomalies in a patient's ventilation occur that may cause collapse of the patient's lungs during parts of their breathing cycle other than at the end of the expiratory phase. As shown in figure 12, in a preferred embodiment, a blower 200 is provided for providing a minimum or background CPAP pressure via a separate dedicated CPAP duct 205 to a CPAP check valve 206, which is a one way valve that allows CPAP pressurised air through from the blower to the patient when the pressure in the patient interface is lower than the CPAP pressure. This arrangement is the subject of an application

PCT/IB2010/054899 and associated applications by the same applicants, and is incorporated by reference. It is envisaged that this CPAP pressure may be controlled by the controller by controlling the blower to provide a constant CPAP pressure. Once the CPAP blower is set to the best practice CPAP pressure for a particular patient, it is envisaged that this pressure will remain constant. Pressure from the blower can be presented to the patient in a variety of ways. Such a blower could be fitted to any of the embodiments shown in figures 1-11 to feed into the primary inlet 17. Figure 26 shows a typical graphical reading of a respiratory cycle without CPAP (showing tidal volume and pressure over time). Figure 28 shows the same graph with CPAP pressure provided as a minimum pressure.

In one embodiment, for example as shown in figure 1 and 13, the one way valves of the pump may be sensitive enough to be opened by the CPAP pressure generated by the blower. When the pressure within the pump is lower than CPAP, then the CPAP pressure will enter the pump and thereafter the patient interface to maintain a CPAP pressure in the patient interface.

In the embodiment shown in figure 12, the resuscitator may be provided with a separate conduit in fluid communication with the patient interface. The fluid conduit is provided with a one way valve, preferably at an end closest to the patient, and more preferably at the mask.

When the pressure in the mask is above CPAP pressure, the one way valve is held closed. When the patient is in their expiratory cycle, pressure will be high enough to open an exhaust valve to allow expiration gases to flow out of the mask. Towards the end of the expiratory cycle, pressure in the mask would drop to ambient pressure, or even lower at the start of the inspiratory cycle. As soon as the pressure drops to below the CPAP pressure, the CPAP pressure will cause the one way valve to open, and maintain pressure within the mask at CPAP pressure.

In this way, and as will be explained below, the inspiratory parameters of tidal volume, pressures and respiratory (breath) rates can be controlled against a background minimum CPAP pressure.

Alternately or in addition, CPAP or PEEP pressure can be maintained throughout the breathing cycle by controlling movement of the piston as will be explained below.

In a "PEEP" mode (positive end expiratory pressure) parameters can be preset by using the controller or the display panel PEEP so that the minimum pressure at the end of the expiratory cycle is controlled by the voice coil actuator and /or the controller controlling movement of the motor and piston as will be described below . In one embodiment, the voice coil actuator 24 will exert a closing force to the exhalation valve to close it when the end expiratory pressure has dropped to the predetermined PEEP pressure. The PEEP pressure is measured by the airway pressure sensor 31. The controller 3 will activate the voice coil actuator 24 when the expiratory airway pressure has reached the predetermined level.

In operation of the resuscitator shown in Figures 1 and 2, the tidal volume delivered to the patient can be preset by the controller 3 or the display panel 4. The tidal volume is controlled by the stroke length of the piston 10. Tidal volume is delivered to the patient on the delivery stroke of the piston 10. In one embodiment, it is envisaged that and exhalation for the patient may be facilitated during the retraction stroke of the piston 10, although this is not generally regarded as best practice. Accordingly one inhale and exhale of the patient may occur during a movement of the piston 10 from one starting point to its opposite end travel and back to the starting point. Alternately, for very small patients, several tidal volumes may be delivered during a single stroke of the piston, depending on the piston size and stroke length. For a given cylinder size, the longer the stroke of the piston, the greater the tidal volume that can be delivered in a single stroke.

Alternately, several delivery strokes of the piston may be used to deliver a single required tidal volume. In such a case, the piston will be accelerated from the end of its delivery stroke to the start of its delivery stroke as quickly as possible to try and provide a relatively seamless flow of gas. The controller 3 instructs the motor 13 to move the piston 10 a predetermined distance at a predetermined velocity.

Feedback from the airway pressure sensor 31 and a flow and tidal volume sensor

36 can provide further control. These sensors may vary normal operation of the piston 10 and/or voice coil actuator 24 from conditions of operation predetermined by an operator and instructed to the device via the display panel 4 and/or controller 3. The stroke length and position of the piston 10 may in addition be monitored by a sensor (a piston position sensor) of or associated with the motor 13 and/or piston 10. The operation of the resuscitator will control the breath rate and inhalation/exhalation ratio.

The breath /respiratory rate and inhalation/exhalation ratio can be preset by using the controller and/or display panel and may be controlled at least in part by a timer of the controller. Patient dependent parameters may also control operation. For example, input information into the controller 3 may include a patient's weight and age. Such control sequences are discussed in more detail below.

In a situation where the airway pressure sensor 31 senses that the maximum predetermined airway pressure has been reached, the controller 3 can instruct the motor 13 to slow (decelerate) or stop, while maintaining the same pressure. This can result in a maintaining of the maximum predetermined airway pressure for the duration of the inhalation time period. In the event of an overpressure or system failure, a safety valve 37 will be actuated to open and relieve pressure on the patient airway. The safety valve 37 may be a passive valve that has predetermined operating conditions. Alternatively it may be a safety valve connected with the controller 3 and controlled by the controller for operation. Alternative to the safety valve 37, the airway pressure sensor 31 and/or flow and tidal volume sensor 36 may communicate with the controller 3 to direct movement of the voice coil actuator in instances where undesirable conditions are being sensed to thereby relieve pressure and/or flow by exhausting gas through the opening 29.

This first form of resuscitator described as well as the form yet to be described allows for data from the airway pressure sensor 31, the piston position sensor, the flow and tidal volume sensor 36 and from a timer to be used to record operating data and performance. A graphical display on the display panel 4 can also be generated. The graphical display can be used by the operator to monitor performance and determine if leakage, blockage or further adj ustments are required to the resuscitator. The graph and/or related data can be stored to assist in the setup of other life support systems and for clinical analysis. Such statistical information may offer significant benefits to provide better best practice treatments for similar situations in the future.

The electrical connection 15 will ensure that the controller 3 can appropriately control the linear motor to thereby control the position and movement of the piston. The cylinder 11 has an inlet volute 16 that includes a primary inlet 17. It is through the primary inlet that ambient air may be drawing into the inlet volute as the piston displaces inside the cylinder towards the outlet 12. This direction of travel is shown in Figure 1. The piston 10 carries a one-way valve 18 that operates to be in a closed condition when the piston is travelling towards the outlet 12. This will result in a drawing of ambient air into the inlet volute 16. When the piston 10 travels in the opposite direction being a n exhalation direction of the resuscitator, the one-way valve 18 can open to allow for air in the inlet volute 16 to displace into the region between the piston 10 and the outlet 12 as for example shown in Figure 2. The primary inlet 17 may include a one-way valve to assist such displacement through the opening created by the one-way valve through the piston by preventing air in the inlet volute 16 from displacing back out through the primary inlet 17. The gas that has displaced into the space between the piston 10 and the outlet opening 12 can then on the return stroke during the inhalation phase of operation be displaced at least in part through the outlet opening 12 and to the flow control unit 7.

The resuscitator may (for example shown in Figure 3) operate in a supplementary oxygen and CPAP mode. A supplementary oxygen reservoir 40 (that may or may not be connected to supplementary supply via the inlet 41) can be engaged to the primary inlet 17 of the pump unit 6. Rather than drawing ambient air into the pump unit, the oxygen or other gas or gas mixture can be supplied to a patient via the resuscitator under pressure. This will allow the operator to control the delivery of an air/oxygen mixture by the use of for example an external blender. Supplementary gas such as oxygen may be delivered via the primary inlet 17 to the pump unit, under pressure, preferably best practice CPAP pressure. In the event of a failure or the gas supply exceeding the capabilities of the resuscitator, then a safety valve 42 may open to exhaust gas from at least part of the pump unit 6. A pressure sensor may be located in an appropriate location for these purposes. If a failure occurs with the supplementary gas supply or the primary inlet 17 becomes blocked then a safety valve 43 may open to allow for ambient air to be drawn into the pump unit 6 allowing ongoing operation of the resuscitator despite issues with the supply of supplementary gas.

In a PEEP mode operational conditions can be specified and preset by using the controller and/or display panel. Where the delivery rate and pressure to the

supplementary gas reservoir 40 is set at an appropriate flow level, the ventilator can operate in the CPAP mode. The motor 13 will stop operation and the flow from the supplementary oxygen reservoir 40 will pass through the one-way valve 18 through the one-way valve 21 to the patient interface 8. The airway pressure sensor 31, combined with the controller's control of the piston as described below, will determine the patient's airway pressure.

With reference to Figure 4 there is shown a variation to the resuscitator described with reference to Figures 1-3 wherein a flexible conduit 56 is provided to extend between the pump unit 6 and the flow control unit 7. The flexible conduit 56 may be fitted between the pump unit and the flow control unit to allow for delivery for gas displaced by the piston 10 towards the patient interface 8. Having the flow control unit 7 and airway pressure sensors and tidal volume sensors as well as the safety valve 37 close to the patient's airway, ensures a more accurate tidal volume and pressure delivery. Also the controller can make adjustments for the compliance in the patient mask. Also possible but less advantageous is to provide a conduit 9 that is of a desired length to allow for more distal location between the patient interface 8 and the pump unit 6. However this has the disadvantage of dead space between the features of the flow control unit 7 and the patient interface 8.

The resuscitator of Figures 1-4, wherein the piston is single acting, lends itself particularly to resuscitation and ventilation of neonatal patients. A manageable sized pump unit can be provided wherein in one stroke of the piston a sufficient tidal volume of air can be delivered to a neonatal patient for inhalation. It is desirable for the unit to be relatively portable and therefore size can be a design constraint. However where size is not an issue, the pump unit 6 can be scaled up so that single delivery stroke of the piston can deliver a sufficient tidal volume of gas to larger patients. However this will increase at least the size of the pump unit 6 making it less convenient for portability purposes.

An alternative configuration of resuscitator may be utilised where size can be smaller. This resuscitator is shown for example in Figure 5. The resuscitator 101 preferably includes a patient interface 108, flow control unit 107 and related components that are preferably the same as those described with reference to the resuscitator of Figures 1-4.

This alternative form of resuscitator also includes a pump unit 106. The pump unit 106 varies to the pump unit 6 described with reference to Figures 1-4. There is provided a motor 113 such as a linear motor or servo motor controlled by a controller 103 that may be engaged with a display panel 104. The linear motor operates a piston 110 via a connection such as a connection rod 114 that operates in a cylinder 111. The pump unit 106 includes an inlet volute 116. The inlet volute via a primary inlet 117 can draw air or supplementary gas supply therethrough as a result of the action of the piston and into the inlet volute 116.

The cylinder includes two openings capable of being in communication with the inlet volute 116. A first opening 160 is provided on the extension side of the piston 110. A second opening 161 is provided on the retraction side of the piston 110. The opening 160 is closable by a one-way valve 162. The opening 161 is closable by a one-way valve 163. The one-way valve 162 is able to assume an opening condition during the retraction stroke of the piston and is in a closed condition during the extension stroke of the piston. The one-way valve 163 is able to assume an open position during the extension stroke of the piston and is in a closed condition when the piston is retracting. On the extension side of the piston 110 is an outlet opening 164 of the cylinder 111. The outlet opening is closable by a one-way valve 165. The one-way valve 165 is in a closed condition during the retraction stroke of the piston and is able to assume an open condition during the extension stroke of the piston. The one-way valve 165 hence essentially works in an opposite mode to the one-way valve 162 to the cylinder. The outlet opening 164 is able to create a fluid connection of that part of the cylinder on the compression side of the piston with an outlet volute 166. The outlet volute 166 includes an outlet opening 112 through which gas displaced by the piston can pass to the flow control unit 7. The outlet volute 166 is separated from the inlet volute 116. The housing of the pump unit 106 may include both the inlet volute 116 and outlet volute 166 and partitions 167 and the cylinder 111 may separate the volutes. On the retraction side of the piston 110 the cylinder includes an opening 168 to the outlet volute 166. The opening 168 includes a one-way valve 169. The one-way valve is positioned so that during the retraction stroke of the piston, gas can displace on the retraction side of the cylinder through the one-way valve 169 into the outlet volute 166. The one-way valve 169 will assume a closed condition during the extension stroke of the piston 110.

In operation during the extension stroke of the piston as shown in Figure 6, the one way valve 163 opens allowing for air to be drawn into the retraction side of the cylinder. Air on the extension side of the piston during the extension stroke can be displaced through the one-way valve 165 to be delivered into the outlet volute. One-way valve 169 will be closed thereby only offering one outlet to the outlet volute 166 being the outlet 112. During the extension stroke of the piston the retraction side of the cylinder is charged with gas being drawn through the one-way valve 163. When the piston travels in its retraction stroke as shown in Figure 7, gas that has been drawn into the retraction side of the cylinder may then be displaced through the one-way valve 169 into the outlet volute 166. The one-way valve 163 will close during the retraction stroke thereby creating only one outlet from the cylinder on its retraction side, namely the opening to discharge the gas into the outlet volute 166. During the retraction stroke the one-way valve 165 is closed thereby offering only one outlet for gas being delivered into the outlet volute, namely being the outlet opening 112. During the retraction stroke the extension side of the cylinder is charged with gas from the inlet volute 116 via the one-way valve 162 that is in that condition opened. As can be seen the pump unit 106 hence operates in a double acting manner. Both during the extension and retraction stroke of the piston gas is displaced towards the opening 112 for delivery towards the patient. With the use of a linear motor or servo motor having high frequency capabilities and accurate and immediate start and stop timing, a high frequency operating piston can deliver gas to the patient in effectively a continuous manner during both the retraction and extension strokes. Each tidal volume delivered to the patient may involve a high number of strokes of the piston. This allows for a compact and preferably portable unit to be provided. Upon exhalation of the patient the flow control unit 107 may be operated to open the exhaust valve to allow for exhalation to occur may coincide with the linear motor stopping operation. Alternatively the linear motor may continue oscillating the piston but where a waste valve may be opened to discharge displaced air from the piston from reaching the flow control valve. Alternatively such wasting may occur via the exhaust valve of the flow control.

With reference to Figure 8 the resuscitator described with reference to Figures 5-7 is also capable of operating in a supplementary gas and/or CPAP mode. This is shown for example in Figure 8. Furthermore an extension conduit 156 may be utilised as shown in Figure 9.

The number of oscillations that the piston may run through can be predetermined. The oscillations determine the tidal volume that is delivered to the patient. An operator may interact with the control unit and/or display to set parameters of operation of the resuscitator. Like the resuscitator described with reference to Figures 1-4 stroke length and position of the piston as well as airway pressures and tidal volume flow and volume sensing may occur and be recorded and displayed.

Figure 13 shows another embodiment of a double acting pump that allows for the pumping of large gas volumes via a single linear motor, with high accuracy and control of the gas pressures, respiratory rates and tidal volumes.

The pump show in figure 13 comprises a plurality of pumping assemblies. Each pumping assembly comprising a piston movable within a cylinder in a reciprocating fashion. Each pumping assembly further comprises a first one way valve and a second one way valve.

The first one way valve is configured for allowing air into a compression zone in its associated cylinder when the piston is moving in one direction, and the second one way valve is configured for allowing movement of compressed gas to exit from the

compression zone for guidance towards a patient interface when the piston is moving in an opposite direction. The pistons each define an aperture for facilitating flow of gas into the compression zone via the first one way valve (although the aperture could also be a recess in the side of the piston. In an alternative embodiment, the aperture could also be located in the side of the cylinder. Each of the second one way valves is disposed at an outlet to their corresponding associated cylinders.

In use the pistons move through a retraction stroke in which a fresh charge of gasses is received into the compression zone through the first one way valve, and a delivery stroke in which the gas in the compression zone is compressed and moved through the second one way valve towards the patient interface.

In this sense, the pump shown in figure 13 is similar to the single acting pumping arrangement shown in figure 1 in that it also comprise a first one way valve and a second one way valve associated with each piston and cylinder assembly, and the first one way valve is disposed on the piston to regulate the flow of gasses through an aperture in the piston.

However, the pump shown in figure 13 differs from the pump shown in figure 1 in that each of the pistons are coupled to opposed ends of the reactor plate of the linear motor, forming two separate, simple cylinder and piston assemblies, which are simple and inexpensive to manufacture, and simple for disassembly and reassembly, for example for maintenance purposes. Further movement of the motor in both directions creates movement of gasses into the patient interface. This means that very little delay between delivery or compression strokes is encountered while the piston is drawing a fresh charge of gas into the compression zone during its retraction stroke. Such a delay may create a pulsing effect, which may not be desirable. As the pump shown in figure 13 is double acting it is capable of pumping twice the volume that a single acting pump would be capable of. This is useful for reducing the size of the pump over all for use in mobile applications such is in ambulances, on the battlefield, or in disaster assistance operations.

The airway pressure may be monitored by a pressure sensor. When the pressure sensor senses that the maximum predetermined airway pressure has been reached the controller then instructs the linear motor to stop or slow to maintain the maximum predetermined airway pressure for the duration of the inhalation period. Alternatively the controller may instruct the linear motor to stop to reduce pressure. In the event of any over pressure or system failure a safety valve like that described with reference to Figures 1-4 may open.

The voice coil actuator may be preloaded so that the exhaust port tends to an open biased condition allowing external air to enter the patient airway.

The resuscitator of Figures 5-9 may also operate in a PEEP mode as previously described.

It is anticipated that in another aspect of the invention, a pump for a resuscitation device as described above may be provided for sale without a patient interface, and may be adapted and configured to be connected or engaged for fluid connection with known patient interfaces. In this respect, any such patient interface may be connected or connectable, or engaged or engageable with the pump.

It is envisaged that such a pump may comprise the features as described above, and may further comprise a controller configured for controlling the position of the piston in the cylinder by controlling the position of the motor to thereby control the tidal volume of the gas delivered to a patient; the pressure of the gas delivered to the patient, and preferably the respiratory rate (or breath rate) of gasses delivered to the patient.

It is anticipated that the pump of a resuscitator may be selected to be single acting or double acting by providing a bypass valve (not shown) for this purpose. In such an embodiment, the bypass valve can open up an outlet (not shown) to vent one of conduits 210a or 210b (used for delivering compressed gas from one of the pump assemblies to the patient interface shown in figure 13) to atmosphere, while closing or at least restricting flow of gas through that conduit. It is envisaged that bypass valve can be controlled by the controller.

In a preferred embodiment, the controller will generally comprise a processor (not shown) for processing data according to a set of software instructions, and digital storage media (not shown) for storing software instructions, a transmitter for sending control signals to the motor and/or controllable valves, and a receiver. In a most preferred embodiment, the controller will further comprise a transmitter for transmitting data (not shown). In a preferred embodiment, the control system automatically controls any or all of the tidal volume of the gas delivered to a patient, pressure of the gas delivered to the patient and respiratory rate of gasses delivered to the patient, or controls them automatically after receiving a few details about the patient.

The controller preferably comprises digital storage means, such as a flash memory, hard disk or the like, for storing digital instructions in the form of software. The digital instructions are configured for instructing the controller to direct control of the relative positions of the two moving parts of the linear motor. Preferably, the instructions are configured for directing the controller to control the tidal volume of the gas delivered to a patient, pressure of the gas delivered to the patient and respiratory rate of gasses delivered to the patient safely and in accordance with medical best practices for a patient.

The controller is configured for receiving data inputs relating to the patient via a receiver (not shown), for example from a keypad or touch screen, or over a data network, which may be hardwired or wireless. The data inputs could include, but are not limited to, one or more selected from the age of the patient, the length of the patient and the weight of the patient. In the case where the patient is a neonate, the use of patient weight is to be preferred, but length may be very important in the absence of any measuring equipment for determining weight (for example in a disaster recovery situation).

In addition to receiving data inputs, the controller comprises a receiver (not shown) for receiving input signals, for example from distance transducers or pressure

transducers, flow sensors; a carbon dioxide sensor; oxygen level sensors (such as a pulse oximeter), thermometer, electrical resistance detectors, voltage detectors, or current detectors.

In a preferred embodiment, a pressure transducer may be located for sensing the gas pressure in the patient interface, or alternatively at the end of a tracheal tube. The distance transducers may provide feedback as to the relative position of one part of the linear motor relative to another part of the linear motor, thereby enabling accurate control of the movement of the linear motor, and hence piston.

In another embodiment, one or more of the resistance detectors, voltage detectors, or current detectors may provide feedback as to the power of the motor and hence enable the work carried out on, or force applied to the gasses in the piston, to be determined.

In this way it is envisaged that control of the pressure being delivered by the respirator device via the linear motor can be provided without requiring a pressure signal from a pressure transducer as feedback. However, this method is not preferred as the closer the pressure is measured to the patient (and preferably within the patient's airways), the more accurate the control of the pressure will be.

Alternatively, the resistance detectors, voltage detectors, or current detectors may be used to determine the relative position of one part of the linear motor relative to another part of the linear motor, thereby enabling accurate control of the movement of the linear motor, and hence piston.

It is also envisaged that the receiver may be configured for receiving updated digital instructions, where, for example, best medical practices (including but not limited to that for tidal volumes, respiratory rates and/or gas pressures for example) have been advanced for one or more groups of patients, and/or the control of the pump has been further refined. In such a way, the pump may be able to receive software "upgrades" to stay current with best practices, by means of a download over the Internet or other network.

In addition to the receiver, the pump further comprises a transmitter (not shown) for sending output signals. The transmitter may be a network card, or a wireless data transceiver that operates, for example on a Bluetooth or Wi-Fi connection.

Such output signals may be sent over a hardwire network or wirelessly over a network, such as the Internet. The kind of output signals envisaged to be sent by the transmitter include (but are not limited to) details of treatment of the patient, such as

· the patients name;

• the patients weight;

• the patient's age;

• the respiratory rate delivered over time;

• maximum and/or minimum respiratory rates;

· the tidal volumes delivered over time;

• maximum and/or minimum tidal volumes

• the pressure fluctuations in the patient interface and/or piston over time; and

• maximum and/or minimum pressures.

It is envisaged that the instructions will be generally configured for directing the controller to carry out a particular sequence of steps in carrying out its function of controlling the pump as will be explained below.

When control of the pressure and/or tidal volumes and/or respiratory rates are discussed below, it should be generally understood that the controller will control the linear motor to move the piston, to thereby control the pressure and/or tidal volumes and/or respiratory rate, unless this is specifically mentioned as being controlled or controllable by another means. Also, when discussing the control sequences and steps carried out the controller in controlling movement of motor to move the piston, it will be appreciated that these generally refer to control of the piston during the inspiratory phase of the patient by pumping more or less gas towards or into the patient interface, unless the movement of the piston is specifically mentioned as happening during an expiratory phase of a patients breathing cycle, or unless logic dictates otherwise.

The preferred embodiments of the invention as described generally comprise a single acting or double acting pump assembly, with each one comprising at least one or more one way valves for allowing flow of compressed gasses from the pump assemblies into or towards the patient interface. In a preferred embodiment, the resuscitation device will not act to withdraw gasses from the patient's airways, ass this currently goes against best practice recommendations. However it will be appreciated that use of the pump assemblies to withdraw gasses during the exhalation or expiratory phase of the patient may be possible.

However, it may in some cases be possible or preferable for gas to be pumped towards or into the patient interface during the expiratory cycle of the patient, and these instances will be specifically mentioned.

Further, where reference is made to the retrieval of information from a data store, whether by interrogation of the data store with initial information or otherwise, the information retrieved from the data store could be retrieved from patient data, algorithms, formulae, data tables or instructions stored in the data store. It will be appreciated that where reference is made to a data store, such a data store could be cloud based, a local data base, a RAM or ROM chip, a hard disk or any other digital storage device.

It is envisaged that the determination of the positioning of the motor, and hence piston, may also require the receiving of several subsignals, including

· a position signal indicating position, a direction signal indicating direction of movement of the piston,

• a velocity signal indicative of the velocity of the piston, and/or

• an acceleration signal indicative of the acceleration of the piston.

The position signal could for example be provided from a distance sensor or transducer, such as a linear encoder or any other suitable sensor. Such suitable linear encoders may be optical (e.g. employing shuttering/Moire, djffr ctjon or holographic principles), magnetic (such as a Hall effect sensor), inductive (such as the Inductosyn™), capacitive or eddy current based.

A further signal that may be utilised is a force signal indicative of the force being applied by the piston to the gas in the cylinder. This could for example be proportionate to the voltage or currency being applied over the windings o f the linear motor.

The controller is configured to retrieve and or receive signals from a data store (preferably by interrogating the data store using input patient details, such as age, length or weight). The received signals may be used as either targets for tidal volume or pressure, i.e. in the sense that the controller tries to achieve those received signals by increasing or decreasing the tidal volume or pressure, or the received signals may be used as threshold signals, i.e. where the controller is configured to generate an alert signal if the pressure or tidal volume exceeds or goes under the threshold values.

It is envisaged that an alert signal as referred to and as will be referred to below may include displaying a message on a monitor, actuating another control process and/or generating an audio or visual alarm. Additionally or alternatively, the generation of an alert signal may generate a control process that presents an operator with an option for allowing a manual override of one or more selected from the maximum best practice pressure, the tidal volume to be delivered to the patient, and the respiratory rate at which gas is to be delivered to the patient.

The instructions in one embodiment are configured for directing the controller to receive a tidal volume signal indicative of the tidal volume of gas required to be delivered to a patient; and determining the number and/or length of strokes and/or proportion of strokes of the piston required to provide the required tidal volume to the patient. The tidal volume signal will be provided from the instructions interacting with a processor and possibly a data store to return a tidal volume signal. There are several ways that the tidal volume signal (for the target tidal volume or threshold tidal volume) can be retrieved, which will be described in more detail below.

Where the received tidal volume signal is to be used as a target value, the controller is also directed by the instructions to control the linear motor to move the piston for the determined number or portion of strokes to provide a required tidal volume to the patient corresponding to the tidal volume signal received.

The controller may do this by calculating the distance and direction that the piston is to be moved, and then comparing the actual distance moved to the distance to be moved, until the difference is zero.

The controller ensures that the piston moves an appropriate distance along the cylinder, whether in one or several strokes, to move a volume of gas corresponding to the tidal volume signal towards the patient. The appropriate positioning of the linear motor is carried out by a position feedback system.

Where the tidal volume signal is used as a threshold, the controller compares the tidal volume that the piston has already displaced against the threshold tidal volume signal, and when the difference is zero, further movement of the piston to displace tidal volume towards the patient is halted (although the piston may still be moved to prepare it for displacing the next tidal volume.

Similarly, in another embodiment as described in more detail below, the controller may receive a target (typically best practice) pressure signal that it is trying to achieve. In such a case, the piston may be moved to displace gas towards the patient, and a signal from a pressure transducer may be used as feedback. The feedback pressure signal from a pressure transducer is then compared to the target pressure signal and when the difference is zero, the target has been achieved. Once the target has been achieved, the controller can move onto the next step of the process. An increased acceleration of the piston may result in an increased pressure "spike" .

The piston may be controlled by the controller to produce pressure spikes of a known value, given the existing conditions in the piston (e.g. temperature, pressure)

Similarly, the piston may be moved to ensure that pressure is retained equal to, above or below a threshold pressure indicated by a threshold pressure signal.

Alternately, in another embodiment it is envisaged that the linear motor could use the voltage across its coils, or alternately the current across its coils, to determine the pressure being exerted on the gas in the piston (since they will be proportional to each other) . This determined pressure may be compared to the received target pressure signal or threshold pressure signal, to determine when the difference is zero (or within a predetermined range). This determination could be used to actuate a next step in a control procedure.

Importantly, the controller is able to control both the pressure and the tidal volumes being delivered by controlling movement of the piston. This allows for the development of several control processes that the applicant believes will be invaluable in simplifying and automating resuscitation of patients in the contexts of mass disaster rescue, warfare and trauma situations, as well as in poorly staffed and resourced conditions in the third world.

In one embodiment the tidal volume signal will be available from best practice information stored in the instructions and/or data store, and preferably retrieved by interrogation of the data store. By carrying out these steps the controller will be able to determine the number or proportion of strokes of the linear motor, and hence piston required to provide a particular tidal volume. Other information may also be required in this determination, such as the piston size being used, the model unit being used and whether the pump is a double acting pump or not. This information may also be stored in the software instructions.

It is envisaged that in the case of a neonatal patient, where a tiny tidal volume is required (current best practice being 4ml to 7 ml per kilogram), only a fraction of a part of a stroke of the linear motor may be required. In the case of a larger adult, several strokes of a single acting or double acting pump may be required to provide the required tidal volume.

Once the required tidal volume has been delivered to the patient, the controller may be directed to stop movement of the linear motor during the exhalation period of the patient, or to retract the piston of a pump that only pumps gas towards the patient when the piston strokes in one direction - i.e. a single acting pump -in order to get it ready for the next stroke.

If the pump is assisting a patient to breath, the patient may be expected to exhale themselves, while the piston remains still during the exhalation period. However, it is envisaged that the pump may be controlled to provide a minimum PEEP pressure during both the inspiration and expiration cycle. In this regard, the software may be configured to direct the controller to accelerate the piston in order to increase or hold the pressure within the patient interface, and hence the patient, at a minimum level. The minimum level may be set by stored best practice instructions for a given patient, and provided as a threshold limit by the instructions.

In order to control the position, speed and acceleration of the linear motor, and hence piston in the piston assembly or assemblies, it is envisaged that the controller will be configured to receive signals from a transducer that are indicative of the location of a moving portion of the linear motor relative to a fixed portion of the linear motor, or indicative of the relative locations of the portions relative to each other. The change in distance or position signal may be measured over time in order to determine speed, and the rate of change of speed over time may be used to determine acceleration. In this way, the distance or position signal can be used as a feedback signal for controlling position, speed and acceleration or deceleration of the piston. Where specific velocities or accelerations are required in order to produce specific pressures or volume follow rates, the required change in position of the piston can be calculated in reverse, using known equations

In general where best practice values are described below, these should be taken as having been retrieved from a data store, preferably by interrogating the data store with input patient details, or if patient details are not available, by retrieving a default best practice value from the data store.

In a preferred embodiment referred to as "auto mode", it is envisaged that the pump will be controlled by the controller on direction of the software in a manner that allows for minimal input by the operator. In this mode, it is envisaged that relatively little information may be input relating to the patient, such as the patient's age, length or weight, if at all. One embodiment of such a sequence is shown as flow chart in figure

20.

Where the resuscitation device is being used to resuscitate a patient with collapsed lungs (for example in neo-natal resuscitation), it is envisaged that the instructions may direct the controller to operate the pump in the following sequence of steps. Initially a signal corresponding to a maximum tidal volume of the patient may received from the data store. The maximum tidal volume may be retrieved from best practice data for a patient's age, length and/or weight.

Initially a maximum piston stroke length limit is determined from the maximum tidal volume to be delivered. The controller from there on ensures that the maximum stroke length, and hence the maximum tidal volume to be delivered, is not exceeded.

As shown in figure 18 and 19 the piston is then controlled to accelerate the piston to generate an initial pressure "p" (shown in figure 19) in the patient interface during an inspiratory cycle of the patient. The slope of the graph of figure 18 will determine the acceleration of the piston. The quantity of the initial pressure may also be selected from best practice data for a patient's age length and/or weight, or set to a default value.

Preferably, the initial pressure is held in the patient interface over a period of time, shown as "t" in figure 18 and 19. It is envisaged that where, for example a patient's lung or lungs are collapsed, or have never been opened, it may be necessary to hold the pressure at a steady state in the patients airways over an extended period of time in order for the lung walls to disengage themselves from each other. This process is described in further detail below as "sigh mode".

The pressure of the gasses in the patient interface and/or patient is received from a pressure transducer, or determined from the voltage or current in the coils of the linear motor, and is monitored .

The controller is directed by the instructions to compare the received pressure signal over time to determine whether the pressure reduces in the patient interface. At the same time, the time at which the initial pressure is being provided is being timed by the controller.

If, after a predetermined period t (which period may be received as best practice data) the pressure has not been released, for example by the opening up of the patient's lungs, then the controller may control the motor and piston to accelerate it to increase the pressure incrementally in the patient and/or patient interface. This incremental increase in pressure is shown as "i" in figure 19. The size of the pressure increment increase can also be provided by best practice information received from the software. The increased pressure is then also timed to see if the pressure reduces within a predetermined time period. If it does not, the pressure is controlled to be incrementally increased again, and so on.

The best practice maximum pressure allowable for a particular patient age and/or weight may also be set as a threshold limit beyond which any further incremental increase of pressure is stopped. It is envisaged that instead of determining whether a pressure is reducing (which it may be doing, but at a very slow rate), the rate that the pressure is decreasing may be determined and compared to a threshold value (from a best practice data set).

It is anticipated by the applicant that patients with larger size lungs will have lungs that tend to open up slower and at a higher pressure than the lungs of smaller patients, or vice versa. This is because the total area over which liquid surface tension holding the lung in a collapsed state, and which is resisting the opening up of the lung, is higher resulting in a larger total pressure required to open the lung. The viscosity of the lung fluids or hardness of the tissue that the lungs are made up of may also affect the rate of release of pressure.

Currently knowledge of such practice is limited due to the lack of information available from cases. It is hoped that the present invention will allow for the recording and transmission of treatment cases for data analysis and research, that will allow for the development of better best practice values. The pressure at which the lung is finally inflated and/or the rate of pressure decrease in the patient interface or patient may be compared to empirical data and /or best practice data to establish a preliminary estimate of the expected size, weight, length or age of the patient for ongoing treatment.

As illustrated in figure 21, if the pressure in the patients airways does decrease by a set quantity (shown as Δρ in figure 21)before the predetermined time period t is up, then the process of incrementally increasing the pressure is stopped, and the next process as described below is controlled by the controller.

Once the pressure in the patient interface and/or patient has been released, or the release rate exceeds a threshold release rate, the piston is controlled by the controller to sustain a delivery of gas at one or more selected from a predetermined pressure, a predetermined respiratory or breath rate and/or a predetermined volume flow rate (or delivery rate), and up until a predetermined best practice tidal volume and/or up to a best practice pressure, after which the piston is stopped (if the piston assembly is double acting) or retracted in preparation for another compression stroke of the piston (if the pump assembly is single acting). The patient is then allowed to breathe out in an expiratory cycle.

The selection of the predetermined pressure and/or predetermined volume flow rate and/or tidal volume can be based on data input by an operator about the patient, or can be determined from an assessment of the pressure release rate and/or the highest pressure at which the pressure release started.

As the piston is moved to sustain a pressure and/or tidal volume and/or volume flow rate, the pressure within the patient interface and/or patient is monitored, and compared over time. The rate of change of pressure is determined and monitored over time by the controller, and compared to predetermined best practice thresholds. If the pressure rises above a certain best practice threshold pressure, or if the rate of pressure increase reaches a predetermined threshold, the movement of the piston may be decelerated, or stopped. A sudden increase in the pressure in the patient interface may indicate that the lungs of the patient have reached their capacity before the best practice tidal volume has been reached, and that further pressurisation or flow may cause barotrauma and/or volutrauma to the patient.

Alternately, such an increase in pressure or rate of pressure change may indicate the presence of a blockage. In such a case, the controller may generate an alarm signal. Such an alarm signal may actuate another control process (such as a process that allows for a manual override by an operator wherein one or more selected from the tidal volume, the inspiratory pressure being delivered by the pump and the respiratory rate is manually settable) and/or may be displayed on a screen, or present as an audible or visual alarm.

It should be kept in mind that while the above explained processes are being performed, the tidal volume may be being monitored, and compared to the upper limit of the tidal volume set initially as explained above. If the tidal volume limit is reached, the piston will immediately be decelerated or stopped completely.

It will be appreciated that if the lungs are very 'stiff' or hard, or there is a blockage of the patients airways, then a small change in movement of the piston in the cylinder may cause a large increase in pressure in the patient interface or patient airway. In such a case, the desired initial pressure may have been reached by the system, but the tidal volume actually displaced into the patient may not be sufficient to cause resuscitation or at least facilitate such.

Similarly, if the desired pressure is reached, but only after an exceptionally large tidal volume is displaced, his may be an indication that there is a leak in the system. In such a case, it is envisaged that the actual tidal volume that was displaced in creating the pressure will be monitored, and if the tidal volume is under or over a best practice threshold, an alarm or alarm signal as described above may be generated.

It is envisaged that where a patient's details, such as age, weight or length

(especially details indicative of the patient's size) are available, then a "best practice delivery mode" can be followed by the controller. One embodiment of such a control sequence is shown as a flow chart in figure 33.

In such a mode, it is envisaged that initially at least some patient's details may be input to the controller. These details can be input to the controller by a user, or transferred electronically from another system. These details are used to interrogate the data store for a set of best practice parameters for the main values of best practice tidal volume, best practice tidal volume increments, initial tidal volume, best practice maximum airway pressure and best practice breath rate or respiratory rate. These parameters can in addition be used with or without CPAP functionality as will be described in more detail below.

It is the intention of the best practice delivery mode to try and achieve the required best practice tidal volume (as a goal or target) while subjecting the patient to the lowest possible pressures. This is because high pressures subject the patient's lungs to higher stresses. A best practice maximum pressure may also be used as a threshold or cut-off parameter beyond which further tidal volume is not pumped by the pump.

In the best practice delivery mode, the resuscitator will initially deliver a relatively small tidal volume to the patient, and gradually increase the tidal volumes delivered in subsequent inspiratory cycles at set increments until a target best practice tidal volume is reached for a patient with those input parameters.

It is envisaged that the set increments will be obtained by interrogating the data store with the input patient parameters above, although the increments could also be set to a default increment value. Similarly, the breath rate may be decreased incrementally until a required best practice breath rate is reached.

It is envisaged that a ramping control process (as will be described in more detail below) may be used to ensure that pressures in the patient airways remain low, and allow for full expiration by the patient (preferably subject to maintaining a CPAP or PEEP pressure) without undesirable build up of pressure in the patients airways.

The tidal volume that has already been delivered during an inspiratory cycle is monitored, and compared to the target best practice tidal volume. If the current tidal volume being pumped is lower than the best practice tidal volume, then it is increased, preferably in increments, until the required best practice tidal volume is reached.

As the tidal volumes are increased, it is envisaged that the respiratory rates will become lower, as the associated expiratory cycle for each inspiratory cycle will take longer. In addition, it is envisaged that the respiratory or breath rate of the patient will be controlled by the controller so that respiratory rate is maximised while avoiding a ramping effect as will be described in more detail below. A higher breath rate can be expected to provide the greatest amount of oxygen to the patient and therefore maximise the patient's chances of survival. The controller will maximise the breath rate by controlling the timing of the inspiratory cycles, and preferably the inspiration to expiration ratio (I: E ratio) while monitoring pressure in the patients airways for ramping.

In one embodiment, it is envisaged that the controller may employ a "sigh mode" .

In such a mode, a relatively low pressure is held maintained in the patient's airways for a predetermined period of time, in order to inflate the patient's lungs quickly while using relatively low pressure. The pressure may be is maintained at or below a particular best practice pressure level (also obtained from the data store according to the patients details) while the patients lungs are inflating. In other words, the piston is controlled to displace sufficient volume to maintain the threshold best practice pressure, even though the lungs are expanding.

When the delivered tidal volume in any one inspiratory cycle reaches the target best practice tidal volume then the piston is stopped (in the case of a double acting pump) or retracted in preparation for another compression stroke (in the case of single acting pump), while the patient exhales in an expiratory cycle. In order to do this, the pressure in the patient's airways and /or patient interface is constantly monitored and compared to the best practice pressure.

If the resuscitator cannot reach the required best practice tidal volume without exceeding a threshold best practice maximum airway pressure, the controller will also stop the piston from displacing further air towards the patient, and it will actuate an alert signal. In such a case, the operator may be presented with an option to override the resuscitator at any time. In figure 35, a graph of an overridden pressure is shown. It is envisaged that the instructions will still set the target best practice tidal volume set as a maximum limit, even if the best practice pressure is overridden temporarily. In such a case, the best practice pressure may be exceeded in an attempt to inflate the patient's lungs, or overcome a blockage, but if the best practice tidal volume is reached, the piston is prevented from displacing further air into the patient's airways. If required, this feature can also be overridden by an operator.

Where the delivered tidal volume is relatively low, especially when measured against best practice tidal volumes for a particular patient demographic, and the pressure increases significantly, this is likely to be more indicative of a blockage than the patient's lung capacity being approached. This is especially the case where the patient's age, length or weight is known, and a better determination can be made by the software instructions of what the patient's tidal volume range should be. It is envisaged that the controller may be directed to interrogate the data store using the relative proportions of tidal volume delivered to patient airways pressures, in order to gain an indication of the possible problem. An example of a blockage reading of tidal volume and pressure over time is shown in figure 27. As may be seen, a large pressure rise for a relatively small tidal volume (especially for larger adult patients) could indicate a blockage.

Where the pressure rise is indicative of a blockage then an alert signal may be generated. Such an alert signal may be used to display a message on a monitor, actuate another control process, and/or generate an audio or visual alarm. In such a case, ventilation may need to be stopped by the operator, and the obstruction physically removed. The operator can also be presented generally with a manual override option to set a higher pressure to be provided to the patients airways, for example if the patients lungs are stiff or not compliant, or if the fluid associated with the patients lungs is sticky or viscous (for example if the operator is very experienced or knowledgeable and is confident that such an override is what is required).

Once the best practice pressure is overridden, the increased pressure is provided in the patient interface by moving the motor, and hence piston to provide this increased pressure. However, if the increased pressure does result in the sudden inflation of the patient's lungs, with a corresponding decrease in back pressure, the resuscitator will ensure that the required best practice tidal volume is not exceeded.

Further, once the lungs are inflated, and the lung walls are no longer sticking to each other, it is envisaged that the next inspiratory cycle will not require the same amount of pressure to be able to inflate the lungs with the same tidal volume.

The instructions may be configured to direct the controller to use an increased pressure for only a limited number of cycles, or indefinitely, until the operator manually changes it back to best practice delivery mode.

It is further envisaged that when being operated in such a best practice delivery mode, the controller will initially be directed by the software to retrieve a best practice initial respiratory or breath rate signal from a data store. The initial respiratory rate signal is indicative of a best practice initial respiratory rate. The best practice initial respiratory rate could also be provided after interrogation of the data store using input patient details like length, weight or age, if any are available

Another embodiment is envisaged where the pump may be controlled by the controller on direction of the software where no input of a patient's details is envisaged. This process is referred to as "auto mode".

Such an auto mode would be useful, for example in situations where time is of the essence and time-consuming inputs of patient details are not possible, or where the operator is not trained or has very little experience in operating a resuscitator. Examples of such instances could be on a battlefield, in third world situations or in mass disaster recovery situations, where the medical equipment may not be used by trained or experienced operators. One embodiment of such an auto mode control sequence is shown as a flow chart in figure 34.

In auto mode, it is envisaged that the control of the pump to achieve a relatively safe resuscitation process, yet a process in which the patient is given a good chance of survival, may preferably be achieved automatically without input and/or receiving any of the patients details by the controller. In such a case, it is envisaged that the automatic control of the pump may preferably require an automated assessment of the lung capacities and parameters of the patient, based on feedback from initial processes carried out. In other words, the patient response to the process may determine the next steps to be taken.

In auto mode, as the controller is not presented with any of the patients details, and therefore has no data with which to interrogate the data store for best practice guidelines, the controller preferably uses a "coverall" best practice maximum pressure (for example for either adults or neonatal patients or both) as a guide to its operation.

The basic functionality of auto mode is that the controller will try to achieve the best practice maximum pressure, by controlling the pump to initially deliver a small initial tidal volume, or series of initial tidal volumes, at a high respiratory rate, and determining the patient's response to the delivered initial tidal volume(s). The subsequently delivered tidal volumes are then increased incrementally. The pressure in the patient's airways is maintained under the best practice maximum pressure as a default (although a manual override is envisaged as being available should it be required). The measured feedback from the delivered initial tidal volume will dictate the next step of the process. It will be appreciated that the accurate and fast control of the linear motor, and hence the pump, allows such control sequences to be viable and adjusted in real time, from breath to breath, in response to such sensed feedback.

The controller will control movement of the motor, and hence piston, to deliver an initial tidal volume, and then subsequent tidal volumes in subsequent respiratory cycles. This initial tidal volume may be a default setting for auto mode, and which may be very small (for example 1ml). In this way, if the patient is a small baby such as a neonatal patient, immediate damage is avoided by barotrauma or volutrauma. It is envisaged that the controller will then control the pump to incrementally increase the tidal volume delivered to the patient.

It is envisaged that before, during and after such delivery of each tidal volume, the pressure in the patient interface and/or the patient's airways (for example in a tracheal tube) will be constantly monitored by receiving a pressure signal from a pressure transducer in the patient interface and/or the patient's airways.

In one embodiment, the pressure at the start of the delivery of the tidal volume and after delivery of the tidal volume will be received and compared, preferably to determine a pressure difference.

In another embodiment, it is envisaged that the pressure may be monitored throughout delivery of the tidal volume, and the rate of change of pressure determined (for example corresponding to the slope of the line on a pressure time graph).

Different aspects of the rate of change of pressure may be monitored, such as the maximum rate of change of pressure throughout the delivery of the tidal volume, the minimum rate of change of pressure, and the average rate of change of pressure during any portion of the delivery. This pressure difference or rate of change of pressure may be used to interrogate the data store to retrieve any one or more of a subsequent tidal volume, a tidal volume increment, a subsequent breath rate and a breath rate increment. In interrogating the data store, other details associated with the initial tidal volume and pressure difference may be used in order to retrieve a subsequent tidal volume or a tidal volume increment.

It is further envisaged that the inhalation to exhalation ratio (I: E ratio) may be controlled and may also be changed from inspiration cycle to inspiration cycle.

Once the subsequent tidal volume and/or subsequent breath rate; or tidal volume increment and/or breath rate increment is received from the data store, the controller controls the motor to move the piston to deliver a subsequent tidal volume at a subsequent breath rate. The controller may add the tidal volume increment to the initial tidal volume to obtain the subsequent tidal volume to be delivered. The breath rate increment will preferably be subtracted from the initial breath rate.

Increasing the tidal volume will also take longer to deliver (while retaining safe pressures in the patient interface), and therefore a reduction of the respiratory rate will typically also be an outcome of increasing the tidal volume (but need not necessarily be).

If a tidal volume is delivered, and the pressure does not change significantly, this may be indicative of the fact that the patient's lung capacity far exceeds the tidal volumes being delivered. In such a case, it is envisaged that the pressures before and after delivery of the tidal volume may be compared, and the pressure difference may be used to interrogate the data store for a new best practice tidal volume, or tidal volume increment that may be added to the last delivered tidal volume.

However, it is also envisaged that in some cases, a low increase in pressure may be indicative of a leak in the system - for example if the patient mask is not sealing onto the patient's face properly. The resuscitator and controller may in addition be configured for detecting such leakage as will be discussed in more detail below.

If a tidal volume is delivered, and the pressure increases significantly, then this may indicate that the tidal volume of the patient is being approached, or alternately that there may be a blockage in the patient's airways. At any stage if the maximum best practice pressure threshold pressure is reached, the motor and piston will stop, and preferably an alert signal will be actuated.

As described above with reference to the pre programmed delivery mode, where the delivered tidal volume is very low, and the pressure increases significantly, or the rate of pressure change is above a threshold rate of change of pressure, this may be more indicative of a blockage than the patient's lung capacity being approached.

Where the pressure rise is indicative of a blockage then an alert signal may be generated. Such an alert signal may be used to display a message on a monitor, actuate another control process, and/or generate an audio or visual alarm. If on or during delivery of the tidal volume a predetermined threshold maximum pressure limit is reached, the controller will control the motor to stop or at least decelerate the piston to prevent this threshold pressure being exceeded.

In one embodiment, the breath rate or respiratory rate is controlled by the controller in a manner that allows a minimum pressure to be attained during the expiratory cycle before starting the next inspiratory cycle, in order to avoid ramping. Where CPAP or PEEP functionality is provided by the resuscitator, as will be described in more detail below, then this minimum pressure will be the CPAP pressure or PEEP pressure. The ramping control process will be explained in more detail below.

It is envisaged that a "sigh mode" as described above and below may also be used, to maintain the best practice maximum pressure over a predetermined time period, to fill the patient's lungs with air quickly. This may particularly be the case where the initial patient response (for example pressure rise) to an initial tidal volume delivery is very little. The predetermined time period over which the pressure is maintained during sigh mode may also increase with each respiratory cycle.

Once the maximum best practice threshold pressure is reached, without there being a blockage, it is envisaged that the last delivered tidal volume will be set as the preferred respiratory cycle tidal volume, and the movement of the motor will be controlled to deliver the same tidal volume during an inspiratory cycle of the patient as was delivered before the predetermined threshold best practice pressure or rate of change of pressure was reached, and at the same respiratory rate (subject to no ramping effect being detected subsequently).

At this stage, it is also envisaged that the operator will be alerted to the current status of the resuscitation, by informing them of the tidal volume, pressures, and/or breath rate, and preferably of the change in process.

It is further envisaged that when being operated in such an auto mode, the controller will initially be directed by the software to retrieve a default initial respiratory or breath rate signal from a data store. It is further envisaged that, similarly to the best practice deliver mode, in auto mode the controller will control the breath rate in an attempt to maximise the breath rate (e.g. in number of breaths per minute) while ensuring that ramping does not occur, subject to the use of sigh mode to fill the patients lungs as quickly and safely as possible. This is done to ensure that the most air (and hence oxygen) is delivered to the patient to enhance the likelihood of the patients survival or recovery.

It will be appreciated that the best practice or default initial respiratory rate signals need not be an actual rate - but could be indicated as a time period between the start of an initial inspiratory cycle and the start of a subsequent respiratory cycle, a number indicating the number of inspirations in a time period (e.g. minute rate), or frequency. As mentioned above, in addition to the respiratory rate being controlled, it is envisaged that the ratio of inspiration time to expiration time (I: E ratio) will be controlled. It may be set as a default ratio, or may be changed according to best practice.

However, depending on the results of the comparison of the initial pressure and the subsequent pressure in the patient airways and/or patient interface (i.e. before and after delivery of a tidal volume), the data store can be interrogated for a new respiratory rate, or for a suitable increment by which the respiratory rate is to be changed.

Where, for example, the pressure has not changed significantly between delivery of tidal volumes, this may indicate that the lung capacity is much larger than the delivered tidal volume.

In such a case, the respiratory rate may be reduced to deliver larger tidal volumes- possibly by using the sigh mode control process- at a lower breath rate, to ensure that a sufficient volume of gas is delivered to the patient's airways.

Where a significant change in pressure is detected after the delivery of a

subsequent tidal volume, or the rate of change of pressure is high, then it is envisaged that the respiratory rate (eg in number of inspirations per minute) may be decreased by a best practice amount. A large increase in pressure may be indicative of "ramping" in a patient. This is where the patient has not fully exhaled before the next inspiratory cycle starts, which may cause an increase in pressure in the patient's airways with each consecutive inspiratory cycle. A control sequence for controlling ramping is described in more detail below.

A respiratory rate increment signal indicative of a best practice change of respiratory rate will be returned from this interrogation, and this respiratory rate increment signal will be used to calculate the subsequent respiratory rate (or time period to the start of the next inspiratory cycle). Such a calculation may be by adding or subtracting the respiratory rate increment signal from the frequency of the present respiratory rate, or the period of the initial respiratory rate.

The controller will then direct the motor to move the piston to deliver the next tidal volume after an appropriate time interval that will result in the desired subsequent respiratory rate.

However, it is envisaged that in controlling the respiratory rate, the controller will take the effects of ramping into account as will be explained below.

It is further envisaged that in the auto mode, leak detection control sequences will be employed, as will be described below in more detail.

As described in this specification, it is envisaged that there may be scenarios where a "sigh mode' becomes applicable. In sigh mode the controller will control movement of the motor to move the piston to deliver a tidal volume to a patient at a constant target pressure. The tidal volume is indefinite in that controller will continue delivering gas to the patient as long as the pressure does not exceed a maximum threshold pressure. How the target pressure is determined may vary according to the specific scenarios as described.

As part of the sigh mode control sequence, the controller controls the motor to deliver an initial tidal volume to a patient during an initial respiratory cycle, after which an initial airway pressure signal indicative of the pressure in the patient's airways will be received from a pressure transducer. The controller will then control the motor to deliver a subsequent tidal volume during a subsequent respiratory cycle, after which a subsequent airway pressure signal will be received that is indicative of the pressure in the patient's airways after delivery of the subsequent tidal volume. The initial airway pressure signal and subsequent airway pressure signal will preferably be measured at the end of the respective inspiratory cycles.

The difference between the initial airway pressure and the subsequent airway pressure may be determined and used to interrogate a data store for the target pressure. Alternately, both the initial airway pressure and subsequent airway pressures may be transmitted to the data store as part of interrogation.

In addition to receiving a target pressure, a maximum threshold pressure may also be received. The target pressure may be used as a target point at which a tidal volumes is to be delivered, and around which pressure may fluctuate as part of the control sequence, while the maximum threshold pressure may be set as a cut off value, which if exceeded causes the controller to control movement of the motor and piston to prevent further delivery of gas the patient, and to trigger the start of the expiratory cycle.

However, it is also envisaged that the target pressure, or a proportion of it (for example 120%) could act as a threshold maximum pressure limit.

In any respiratory control sequences, including any of the above control sequences such as auto mode, or best practice delivery mode, a problem may occur that that during the expiratory cycle, the lungs of the patient may not be fully exhausted before the controller causes the motor to move the piston to start the respiratory cycle again. If the lungs are not exhausted to the required extent, then the start of a new respiratory cycle may cause a build up of pressure at an elevated rate in the patient's airways, or an increased pressure in a patient's airways with each breath. A graph of tidal volume and pressure over time illustrating ramping is shown in figure 29.

For this reason, in one embodiment it is envisaged that the instructions will be configured for detecting and preventing ramping, unless it is specifically required to increase pressure. A flow chart illustrating an embodiment of such a control sequence is shown in figure 23. Any of the control sequences shown in the figures may be used in cooperation with each other. It is envisaged that the control sequence used to avoid ramping will be used in conjunction with the auto mode control sequence described above.

The instructions are configured for directing the controller to interrogate a data store for a best practice predetermined ramping pressure signal. The interrogation could be based on input patient's details, or could be a default value. Alternately, the ramping pressure signal could be the pressure signal detected by a pressure sensor at or around the inlet of the pump, or in the separate CPAP conduit described above. This pressure may be provided as a CPAP pressure source such as a blower as described above.

A patient pressure signal is also received from a pressure transducer sensing pressure in the patient's airways, or in the patient interface. During the expiration cycle, the controller will control the motor, and hence the piston to stop, or alternately pull back or retract in preparation for another compression stroke during the next inspiratory cycle.

During the expiration cycle, the patient pressure will drop in the patient interface and the patient's airways. The patient pressure drop will be monitored by the controller, and the controller will compare the received patient pressure signal to the ramping pressure signal.

The controller will then control movement of the motor to move the piston to deliver a subsequent tidal volume during an inspiratory phase of a patient, only after the received patient pressure signal has dropped to a level equal to or below the received ramping pressure signal. In this way, the resuscitator can ensure that no ramping of pressure occurs during resuscitation.

It is envisaged that at the same time, the controller will time the time passed since the beginning of the expiration cycle. The time that has passed will be compared to a threshold maximum expiratory time signal. The threshold maximum expiratory time signal could be determined as a best practice ratio of the last inspiratory cycle, or may be retrieved from the data store, preferably by interrogating the data store using patient details.

Where the time taken for the last expiratory cycle exceeds the threshold maximum expiratory time signal, this may indicate a problem that will cause ramping of the subsequent pressures delivered to the patient, and an alert signal may be generated.

In one embodiment, it is envisaged that no CPAP pressure may be provided by the resuscitator, and the ramping pressure signal used may be ambient pressure.

In another embodiment, the exhaust valve may be controlled to provide a minimum PEEP pressure, and the minimum PEEP pressure may be used as the ramping pressure signal.

A particular problem is encountered in the resuscitation of a patient with collapsed lungs, or with patients with lungs that have never been filled (as with neonatal patients. An initially high pressure is required to initially inflate the lungs, but once the initial inflation has occurred, the pressure required to maintain a required volume flow rate is much less. Gas at pressure tends to flow in at a high flow rate under pressure, and with little control. It is therefore desirable that the pressure at which the lungs are inflated can be reduced.

For this reason, in one embodiment the instructions will be configured for controlling the linear motor, and hence the piston, to move linearly, at a controlled average speed along the cylinder, but while accelerating it and decelerating it in an oscillating fashion (preferably rapidly) to create small 'micro pulses' of pressure in the gas being delivered to the patient. A graph of one example of the piston displacement versus time is shown in figure 18. Figure 19 also shows a graph of the pressure versus time for this process.

While the tidal volumes and respiratory rates may remain controlled at best practice levels, it is anticipated that the pressure pulses being created by the piston in the patient interface will be sinusoidal and in the nature of an oscillation, but will remain at an average pressure preferably just below or at the best practice threshold levels. The best practice threshold levels can be obtained by interrogation of the data store with the patient's details, from details of pressure responses as detailed above, or set as a default maximum pressure.

Further the maximum pressures of the pressure pulses can be controlled to remain below or at best practice levels.

It is anticipated that the provision of such oscillations in the patient's airways may encourage the separation of the patient's lungs from itself, and may assist in overcoming the water surface tension forces that prevent the lungs inflating. It is anticipated that the provision of such oscillations may allow for the reducing of the average pressure required to inflate the lungs, thereby reducing the potential for barotrauma on inflation of the lungs.

It is a particular problem with currently known resuscitator devices that when they apply a high initial pressure, once the lungs inflate suddenly, they have a tendency to continue inflating the lungs at the same high pressure, or at a high flow rate. If the lungs become substantially filled with air, the pressure may to increase suddenly, causing barotrauma or volutrauma to the patient.

Further, if the pressure is reduced immediately after inflation of the patient's lungs, but the tidal volume being delivered into the patient's lungs is higher than the capacity of the patients lungs, then volutrauma can occur.

By controlling the maximum tidal volume that can be pumped to a best practice capacity, and immediately stopping any further movement by the piston on detection of a pressure increase, or a high rate of change of pressure, it is hoped that such occurrences of volutrauma and/or barotrauma can be reduced. Even where the maximum tidal volume is controlled, it is anticipated that it will be desirable to be able to more efficiently inflate a patient's lungs by providing oscillations or pressure pulses in the delivered gasses.

As described above, it is envisaged that the resuscitator can provide for a CPAP minimum pressure to be provided to the inlet to the piston assembly, in order to ensure that the minimum pressure provided to the patient is held at least at the CPAP minimum pressure. This may also be applied during any of the control sequences described in this specification.

However, it is envisaged that such provision of pre -pressurised gas to the inlet of the pump may be problematic in that, when the piston in the pump is being controlled to deliver a particular tidal volume of gas, that tidal volume is can be directly related to the volume of air displaced by the piston in a compression stroke. The tidal volume delivered to a patient is delivered into the patient's airways at ambient pressure, or very close to this. If a pre-pressurised volume of gas is delivered to patient, then by the time it de- pressurises inside the patient, the volume that will have been effectively delivered will be larger than the actual swept volume of the piston(s) in the cylinder,

In the case of neonatal patients, where the tidal volumes to be delivered are tiny, this depressurisation and expansion of the pre-pressurised gas can be undesirable.

For this reason, it is envisaged that software will be configured to direct the controller to take such pre-pressurisation of the gas or gasses into account when determining the volume to be swept by the piston, so that the tidal volume delivered to the patient is at the desired best practice level. An embodiment of such a control sequence is shown in figure 24.

It is envisaged that in order to do so, the controller will receive an inlet pressure signal indicative of the pressure of the gas being received into the cylinder (i.e. before it is acted on by the piston).

The software will then direct the controller to determine a compensated tidal volume to be provided at ambient pressure to a patient. Such a determination could be carried out on the basis of calculating the compensated tidal volume through using known thermodynamic algorithms, in such a determination, it is envisaged that the ambient temperature, or the temperature of the gas at the inlet could be taken into account.

Alternately, a simple interrogation of a data store could be carried out by the controller, which returns one or more of a compensation factor or a compensated volume for a given set of initial parameters (such as initial pressure, best practice tidal volume to be delivered, ambient pressure, ambient temperature, temperature at the inlet, flow velocity at the inlet, or the like). Temperature signals may be transmitted by thermocouples placed at appropriate locations, and received by the controller.

It is envisaged that the tidal volume required at ambient pressure may then be multiplied by the compensation factor, to provide a compensated tidal volume, or alternately, the compensated tidal volume as retrieved may be delivered to the patient interface and/or patient's airways

The movement of the motor will then be controlled by the controller to move the piston to deliver the compensated tidal volume to the patient interface, and on to the patient's airways. When this compensated tidal volume is delivered into the patients airways, it will expand to the required tidal volume required as per best practice.

It is further envisaged that the controller may compensate for leakage from the resuscitator, for example from the mask. An embodiment of such a control sequence is shown in figure 25.

In order to control for leakage compensation, it is envisaged that the patient interface will be provided with a flow sensor, or flow transducer. Preferably, the flow sensor is located as close as possible to the patient, so that the flow at ambient pressure is sensed by the flow sensor, although it is envisaged that airflow in the patient interface may also be sensed by a flow sensor.

The flow sensor is configured for sending a flow signal indicative of the flow rate of gas through the patient interface and into the patient's airways. In turn, the controller is configured for receiving the flow signal along with the other signals described above.

The controller is directed by the software to determine a pumped volume that has been delivered by the pump. This is determined by determining what volume of gas was moved by the piston in the cylinder e.g. from the cross sectional area of the piston and the distance moved by the piston.

The pumped volume is determined over a given inspiratory cycle from the geometry and movement (e.g. swept volume) of the piston in the cylinder.

In addition, the flow rate of the gas past the flow sensor is integrated by the controller over the time period of the inspiration cycle to determine a patient tidal volume of gas that was delivered to the patient. The patient tidal volume and the pumped volume are then compared to each other by the controller to see if they coincide. As flow sensors may not be perfectly accurate, small discrepancies may exist between the pumped volume and the patient tidal volume. However, a large discrepancy between the swept volume and the delivered volume may be indicative of a leakage from the system, or a blockage in the patient's airways. If such a discrepancy is revealed, an alert signal may be actuated.

Alternately, instead of actuating an alert signal, it is envisaged that the controller may control movement of the motor to move the piston to increase or decrease the pumped volume in accordance with the comparison of the pumped volume and the patient tidal volume, to thereby compensate for the leaked flow.

In one embodiment where the patient is breathing to a limited extent, it is envisaged that the controller could be directed to perform a triggering sequence of steps that enables triggering of an inspiratory cycle by the software.

In order to carry out this triggering sequence, towards the end of the expiratory cycle, once the patient has fully exhaled, the rate of drop in pressure will stabilise. This will mark the start of the next phase in which the triggering sequence is used to determine when the next inspiratory cycle should start.

The controller will initially receive a an initial patient pressure signal indicative of the pressure in one or more of the patient interface and the patient's airways during an expiratory cycle of the patient. Thereafter, the controller will receive a similar subsequent pressure signal, preferably during the same expiratory cycle. The initial pressure signal and the subsequent pressure signal are then compared to each other by the controller. Preferably, an ongoing series of pressure signals may be received, each pressure signal first acting as a subsequent signal to be compared against the pressure signal before it, and then as the initial pressure signal against which the next signal is compared.

By comparing the initial and subsequent pressure signals, the controller may determine whether the subsequent patient pressure signal has dropped below the initial patient pressure signal by a predetermined amount in order to trigger the start of the inspiratory cycle.

Alternately, the subsequent pressure signal may be compared to a predetermined threshold minimum pressure to determine if the subsequent pressure signal has reached a predetermined threshold minimum pressure in order to trigger the start of the inspiratory cycle. The predetermined threshold minimum pressure may be the CPAP minimum pressure or the PEEP minimum pressure as described above. If the subsequent pressure has reached the predetermined threshold minimum pressure, or the difference between the initial pressure signal and the subsequent pressure signal has exceeded a predetermined threshold, the controller will trigger or actuate the start of the next inspiratory cycle, and the control sequence associated with this.

In an alternative embodiment, the triggering sequence could involve determining when the end of the exhalation occurs by measuring the velocity, speed of flow or direction of flow out of the patient interface by a flow sensor. When the flow or expiratory gasses outward or out of the patient interface reduces to below a threshold flow rate (which flow rate could be a best practice flow rate or absolute flow rate), or if the direction of flow changes from expiration to inspiration (for example if a patient can self regulate to a limited extent) this can actuate the start of the triggering sequence. In this embodiment, the start of the inspiratory cycle is triggered by monitoring the flow sensor, and when the expiratory flow rate drops below a certain amount, or a reverse (i.e. inspiratory) flow is detected, this will trigger the start of the inspiratory cycle. The controller will then control the motor to deliver the next inspiratory tidal volume.

It is envisaged that in another embodiment, the rate of change of the pressure signals (i.e. the slope of the pressure/time graph) may be calculated, and if the rate of change exceeds a predetermined threshold rate of change, this may trigger or actuate the start of the next inspiratory cycle, and the control sequence associated with this. This will typically involve actuating movement of the motor to move the piston to pump gas to the patient to start an inspiratory cycle of the patient.

It is envisaged that the controller may monitor the total time that the expiratory cycle has been ongoing, for example by timing it by means of a clock. The controller may retrieve a predetermined best practice maximum expiratory time, for example by using patient details to interrogate a data store, or by determining the best practice maximum expiratory time as a proportion of the inspiratory time. The best practice maximum expiratory time is compared continuously with the actual expiratory time, and if the actual expiratory time is equal to and/or exceeds the best practice maximum expiratory time, the controller can start the next inspiratory cycle by controlling the motor to start a new compression stroke, and/or the controller can generate an alert signal.

It is envisaged that at least one gas level sensor may be located in the patient interface, and preferably at or towards the mask, in order to detect levels of carbon dioxide and/or carbon monoxide, or any other relevant gas. The controller will be configured to receive gas level signals from such sensors, that are indicative of the levels of gas detected by the sensor in the patient interface.

The controller may be configured to retrieve a best practice gas level signal from a data store, which may be obtained by interrogating the store using patient's details as described above. The best practice gas level signal may indicate a best practice range for gas levels for a patient as per the input patient's details.

The gas level signal received from the sensor will be compared to the best practice gas level signal received from the data store. If the gas level signal received from the sensor does not approximate the best practice gas level signal, or fall within the retrieved range of acceptable best practice gas levels, then this may indicate that the patient interface is not properly located. As an example, if the patient interface is a tracheal tube, this may indicate that the tracheal tube is not properly inserted down the trachea, and may instead be located in the oesophagus.

In such a case an alert signal may be actuated.

It will be appreciated that two or more of the control sequences, steps and methods described may be used in a complementary fashion with others. In addition, alternative signals may be received and used by the processor to assist and/or facilitate in the making of decisions as to which control procedure to use. In one preferred embodiment, several signals could be received and used to cross check each other- for example, a temperature signal indicative of the temperature in the patients airways could be used to cross-check or provide additional confirmation as to whether the patient interface has come off the patient, or whether a leakage is occurring; oxygen levels from a pulse oximeter could be used to confirm the triggering of the start of the inspiratory cycle. A flow sensor could be used to confirm readings from a pressure sensor that an inspiratory cycle should be triggered.

Further, when time is of the essence in an emergency situation, where patient parameters cannot be confidently input into the control system, it is believed that the automatic control of resuscitation as described above can be of value.

With reference to the resuscitators in Figures 1-9, parts of the resuscitator may be disposable. In particular those parts of the resuscitator that have been exposed to exhaled breath or air from a patient may be disposable. They may be manufactured and assembled in a way to facilitate their disposable use. For example the patient interface 8, the flow control unit 7 and one way valve 21 and/or the voice coil actuator 24, movable mouth 23 and housing 22 may all be disengageable from the pump unit 6 and be disposed after use. Circuits to allow for a quick connection of the controller 3 to a replacement assembly of such parts may be provided through simple plug/socket arrangement(s). A single plug/socket may be provided. This may automatically become coupled upon the engagement of the disposable components with the pump unit 6.

With reference to Figures 10 and 11 there is shown more detail in respect of the tidal volume and flow sensor. In Figure 10 there is shown the patient interface 208 wherein the flow and tidal volume sensor 236 is shown during the inhalation phase of operation. It is connected to the controller 203 via a connection 283. With reference to Figure 11, the sensor 236 is shown in the exhalation phase. The sensor 236 is of a kind that displaces dependent on air flow past it. Such may not be ideal for accurate sensing due to inertial mass of the sensor.

An alternative form of a sensor is one that has no inertial mass delay

characteristics. An alternative form of sensor that may be used may be a gas flow meter that measure flow thermally. An example of such a flow meter is one manufactured by Sensirion.com such as their digital gas flow sensor ASF1400/ ASF/1430. It may be one that is made in accordance to that described in US6813944. Such a flow sensor has a high response rate, given that it has unlike the sensor of Figure 10, it has no mass to be displaced by the flow. A fast response can be beneficial. Such sensors may commonly be referred to as a hot wire flow sensor or thermal mass flow meters. The sensor or an alternative sensor may also measure the temperature of the exhaled breath. With an appropriate sensor where the response rate is very quick (a matter of, for example one tenths of a second) it is possible during the exhalation of a patient to measure the patient's core temperature. This information may also be collected and/or displayed or otherwise used by the resuscitator.

Further, it is anticipated that the controller will preferably be configured to receive and monitor oxygen signals indicative of the oxygen levels in a patients airways and/or blood from a suitable sensor, for example such as a pulse oximeter. The received oxygen signal can be used as feedback for direct control or confirmation of the efficacy of any of the control processes described above.

The invention may offer the advantages of being portable, hand held (including being able to be held by one hand in order to hold the patient interface in the appropriate condition) and self contained by virtue of including its own power source (such as a battery pack).

The device may have programmable profiles fixed and/or customised to suit patients, clinicians and operators requirements.

A heart rate monitoring facility may also be incorporated with the device, wherein heart rate can be accounted for in the control of the device and be displayed by the device.

The display can assist the operator in evaluating resuscitation of the patient. The performance, operating parameters and status of the features of the device are able to be recorded. This can assist in statistical analysis and to gather information for set-up of other devices.

The patient as herein defined may a mammal such a person or animal.

It will be appreciated that the apparatus as described in this specification, as well as the control processes illustrated and embodied demonstrate the broader concept of a resuscitation device that is able to be controlled to deliver accurate tidal volumes at accurate pressures, which tidal volumes and pressures are changeable from breath to breath of a patient. Further, the control processes allow for varying treatment of a patient, depending on feedback received from a patient in response to previous treatment by the resuscitator apparatus.

The apparatus described not only allows for best practice values to be used to treat a patient, but importantly also allows for accurate recording and storage of previous treatment, and patient responses to this treatment. It is envisaged by the applicant that such accurate recordal and storage of treatment data, together with subsequent analysis of the data, will allow for more effective treatment processes and increasingly accurate best practice values and algorithms to be developed.

Claims

CLAIMS:

1. A method of controlling a resuscitator device, to be carried out by a

controller, the method comprising the steps of

a. receiving one or more patient details;

b. receiving a best practice tidal volume signal associated with a best practice tidal volume to be delivered to a patient associated with the said one or more patient details;

c. controlling the motor to move the piston to deliver an initial tidal volume

during an initial respiratory cycle that is smaller than the best practice tidal volume;

d. controlling the motor to move the piston to deliver an incrementally increased tidal volume in subsequent respiratory cycles, until the delivered tidal volume in a respiratory cycle is equal to the best practice tidal volume.

2. A method as claimed in claim 1, wherein the method comprises the step of:

3. A method as claimed in claim 2, wherein the method comprises the step of:

4. A method as claimed in claim 3, wherein the method comprises the step of:

a. comparing the patient airway pressure to the best practice maximum

pressure.

5. A method as claimed in claim 4, wherein the step of controlling the motor to move the piston to deliver an incrementally increased tidal volume is carried out only if the last delivered tidal volume is lower than the best practice tidal volume and the patient pressure does not exceed the best practice maximum pressure.

6. A method as claimed in claim 5, wherein the step of step of controlling the motor to move the piston to deliver incrementally increased subsequent tidal volume includes the steps of:

7. A method as claimed in any one of claims 2 to 6, wherein the step of receiving an airway pressure signal indicative of the patient airway pressure includes the step of determining the patient pressure in one or more selected from a patient's airway and a patient interface.

8. A method as claimed in any one of claims 2 to 6, wherein the step of determining the patient pressure comprises one or more of the steps selected from :

a. receiving said airway pressure signal from a pressure transducer in a patient interface; and

b. determining the pressure being applied by the piston from one or more

selected from

i. the power across the motor;

ii. the voltage across the motor; and

iii. the current across the motor.

9. A method as claimed in any one of claims 2 to 8, wherein the method comprises the steps of:

10. A method as claimed in any one of claims 1 to 9, wherein the method comprises the step of:

11. A method as claimed in claim 10, wherein the method comprises the step of: a. receiving a best practice respiratory rate signal associated with a best practice respiratory rate for the patient.

12. A method as claimed in claim 11, wherein the method comprises the step of: a. controlling movement of the motor and the piston to initially deliver gas to the patent at the best practice respiratory rate.

13. A method as claimed in any of claims 1 to 12, wherein the method comprises the step of:

14. A method as claimed in claim 13, wherein the method comprises the step of: a. receiving a best practice I: E ratio signal indicative of the best practice I: E ratio for said patient.

15. A method as claimed in claim 14, wherein the method comprises the step of: a. controlling movement of the motor and the piston to initially deliver a respiratory cycle to the patent at the best practice I: E ratio for said patient. A method as claimed in claim 7, wherein the method comprises the step of:

a. receiving one or more selected from

iii. a temperature signal indicative of the temperature of gas in the

patients airways; and

iv. a flow signal indicative of one or more selected from

1. the speed of gas flow through the patient interface; and

2. the direction of gas flow through the patient interface.

A method as claimed in claim 14, wherein the method comprises the step of: a. interrogating a data store, in the event of the delivered tidal volume being lower than the best practice tidal volume, to retrieve said one or more selected from

i. a tidal volume increment signal, indicative of an incremental increase in tidal volume to be delivered in a subsequent respiratory cycle, ii. a tidal volume signal indicative of the increased tidal volume to be delivered in a subsequent respiratory cycle,

iii. a respiratory rate signal indicative of the respiratory rate at which

subsequent respiratory cycles are to be delivered,

v. a best practice I: E ratio for said patient.

A method as claimed in claim 3, wherein the method comprises the step of:

a. receiving, in the event of the airway pressure being lower than the best

practice maximum pressure, one or more selected from :

i. a tidal volume increment signal, indicative of an incremental increase in tidal volume to be delivered in a subsequent respiratory cycle; ii. a tidal volume signal indicative of the increased tidal volume to be delivered in a subsequent respiratory cycle;

iii. a respiratory rate signal indicative of the respiratory rate at which

subsequent respiratory cycles are to be delivered; and

19. A method as claimed in claim 17, wherein the step of controlling the motor to move the piston to deliver an incrementally increased tidal volume, includes the step of delivering said incrementally increased tidal volume at a respiratory rate that is incrementally increased or decreased.

20. A method as claimed in claim 17, wherein the method comprises the step of: a. determining the respiratory rate at which the incrementally increased tidal volume is to be delivered using one or more selected from

i. the respiratory rate signal, and

ii. the respiratory rate increment signal.

21. A method as claimed in claim 17, wherein the method comprises the step of: a. determining an incrementally increased tidal volume to be delivered using one or more selected from

i. the tidal volume increment signal, and

ii. the tidal volume signal.

22. A method as claimed in claim 17, wherein the method comprises the step of: a. controlling the motor to move the piston to deliver an incrementally increased tidal volume to said patient that is incrementally larger than the previous delivered tidal volume an amount associated with the tidal volume increment signal received from the data store.

23. A method as claimed in claim 9, wherein the method comprises the step of:

24. A method as claimed in claim 23, wherein the alert signal includes one or more steps selected from:

the maximum best practice pressure,

the tidal volume to be delivered to the patient, and

the respiratory rate at which gas is to be delivered to the patient; b. displaying a message on a monitor,

c. actuating another control process, and

d. generating an audio or visual alarm.

25. A method as claimed in claim 1, wherein the step of controlling movement of motor and hence the piston to stop further delivery of gas to the patients comprises one or more selected from the steps of:

26. A method as claimed in claim 9, wherein the method comprises the step of:

27. A method as claimed in claim 9, wherein the method comprises the step of:

a. moving the motor to move the piston at a reduced respiratory rate in the

event that the patent airway pressure exceeds the threshold maximum pressure.

28. A method as claimed in claim 17, wherein the method comprises the steps of: a. interrogating a data store in the event that the threshold maximum pressure is exceeded by the patients airway pressure; and

b. receiving from a data store as a result of the interrogation, one or more

selected from

iii. a respiratory rate signal indicative of the respiratory rate at which

subsequent respiratory cycles are to be delivered; and iv. a respiratory rate increment signal indicative of the increment by which the current respiratory rate is to be changed.

29. A method as claimed in claim 26, wherein the reduced subsequent tidal volume is determined from the tidal volume delivered during the last inspiratory cycle and the tidal volume increment signal.

30. A method as claimed in claim 29, wherein the step of interrogating the data store comprises the step of transmitting treatment details to a data store.

31. A method as claimed in claim 29, wherein step of interrogating the data store comprises the step of transmitting treatment details for indexing against one or more selected from

a. an index,

b. patient data,

c. an algorithm,

d. a formula,

e. data tables or

f. instructions

32. A method as claimed in claim 29, wherein the treatment details are any one or more selected from :

d. the received patient details;

e. the tidal volume delivered during any current or prior respiratory cycle.

f. the patients airway pressure at any point during any current or prior

respiratory cycle;

g. the difference between the patient airway pressure at the end of an initial respiratory cycle and the patient airway pressure at the end of a subsequent respiratory cycle;

h. rate of change of pressure in the patient's airways from one respiratory cycle to the next for any current or prior respiratory cycle;

i. I: E ratio for any current or prior respiratory cycle;

j . respiratory rate for any current or prior respiratory cycle.

33. A method as claimed in claim 32, wherein the input patient details relate to one or more selected from the patient's age, weight or length.

34. A method as claimed in any of claims 1 to 33, wherein the method comprises the step of:

a manual override maximum pressure set by the operator;

a manual override tidal volume set by the operator; and a manual override respiratory rate set by the operator.

35. A method as claimed in any one of claims 1 to 33, wherein the method comprises the steps of:

a. controlling movement of the motor and piston to deliver a predetermined

number of inspiratory cycles at one or more selected from

the manual override maximum pressure,

manual override tidal volume, and

manual override respiratory rate set by the operator, controlling movement of the motor and piston to deliver subsequent tidal volumes at the values they were at prior to the manual override.

36. A resuscitation device for delivering gas to a patient in respiratory cycles comprising alternating respiratory and expiratory cycles, said resuscitation device comprising :

d. an accurate positionally controllable motor operatively connected to said

piston to move said piston in said cylinder;

i. the controller comprising digital storage media for storing digital

instructions,

ii. wherein the instructions are configured for carrying out the method according to any one of claims 1 to 35.

37. A method of controlling a resuscitator device, to be carried out by a controller, the method comprising the steps of

b. receiving a threshold maximum pressure signal indicative of a threshold

maximum pressure allowable in a patients airways during an inspiration cycle; c. controlling movement of the motor to move the piston to deliver an initial tidal volume corresponding to the predetermined initial tidal volume signal; d. receiving an airway pressure signal indicative of the patient airway pressure, e. comparing the patient airway pressure to the maximum pressure; and f. delivering an increased subsequent tidal volume if the patient airway pressure does not exceed a threshold maximum pressure associated with the maximum pressure.

38. A method as claimed in claim 37, wherein the method comprises the step of: a. receiving an initial respiratory rate signal indicative of the respiratory rate at which the respiratory cycle is to be initially delivered to a patient.

39. A method as claimed in claim 37, wherein the method comprises the step of: a. receiving and/or determining patient feedback signals from transducers

relating to the state of the patient.

40. A method as claimed in claim 39, wherein the patient feedback signals are one or more selected from :

a. a carbon monoxide signal indicative of the levels of carbon monoxide in the patient's airways or bloodstream during any current or prior respiratory cycle; b. a carbon dioxide signal indicative of the levels of carbon dioxide in the

patient's airways or bloodstream during any current or prior respiratory cycle; c. an oxygen signal indicative of the levels of oxygen in the patient's airways or bloodstream during any current or prior respiratory cycle;

f. a patient airway pressure difference signal indicative of the difference between the patient airway pressure at the end of an initial respiratory cycle and the patient airway pressure at the end of a subsequent respiratory cycle; g. a rate of change of pressure signal indicative of the rate of change of pressure in the patient's airways from one respiratory cycle to the next for any current or prior respiratory cycle;

h. an I: E ratio signal indicative of the I: E ratio for any current or prior respiratory cycle of the patient;

41. A method as claimed in claim 37, wherein the method comprises the step of

a. determining a pressure difference signal indicative of the pressure difference in the patients airways from one inspiratory cycle to the next.

42. A method as claimed in claim 41, wherein the pressure difference signal is indicative of the pressure difference in the patient's airways from the end of the last inspiratory cycle to the end of the current inspiratory cycle.

43. A method as claimed in claim 40, wherein the method comprises the step of: a. interrogating a data store using one or more selected from the pressure

difference signal, the pressure difference, and the patient feedback signals to retrieve one or more selected from

i. a subsequent tidal volume signal indicative of a subsequent tidal

volume to be delivered to the patient in a subsequent respiratory cycle; ii. a subsequent respiratory rate signal indicative of a respiratory rate at which a subsequent respiratory cycle is to be delivered to a patient; iii. a subsequent I: E ratio indicative of the I: E ratio at which a subsequent respiratory cycle is to be delivered to a patient; iv. a subsequent maximum pressure signal indicative of the maximum pressure at which a subsequent inspiratory cycle is to be delivered to a patient.

44. A method as claimed in claim 43, wherein the step of delivering an increased subsequent tidal volume is delivered at one or more selected from

45. A method as claimed in claim 43, wherein the step of interrogating the data store comprises the step of transmitting treatment details for indexing against one or more selected from:

a. an index.

b. patient data,

c. an algorithm,

d. a formula,

e. data tables or

f. instructions

46. A method as claimed in claim 37, wherein the predetermined initial tidal volume signal is a default signal.

47. A method as claimed in claim 37, wherein the method comprises the step of: a. generating an alert signal in the event of the airway pressure being greater than the threshold maximum pressure.

48. A method as claimed in claim 47, wherein the alert signal includes one or more selected from:

i. the maximum best practice pressure,

ii. the tidal volume to be delivered to the patient,

iii. the I: E ratio of the tidal volume to be delivered to the patient; and iv. the respiratory rate at which gas is to be delivered to the patient; b. displaying a message on a monitor,

c. actuating another control process, and

d. generating an audio or visual alarm.

49. A method as claimed in claim 37, wherein the step of controlling movement of motor and hence the piston to stop further delivery of gas to the patients comprises one or more selected from the steps of

a. stopping movement of the motor to stop movement of the piston; and b. controlling movement of the motor to move the piston in said first stroke

direction.

50. A method as claimed in claim 37, wherein the method comprises the step of: a. controlling the motor to move the piston to deliver a reduced subsequent tidal volume during a subsequent respiratory cycle in the event that the patent airway pressure exceeds the threshold maximum pressure.

51. A method as claimed in claim 37, wherein the method comprises the step of: a. moving the motor to move the piston at a reduced respiratory rate in the

event that the patient airway pressure exceeds the threshold maximum pressure.

52. A method as claimed in claim 37, wherein the method comprises the step of: a. controlling movement of the motor to move the piston to deliver one or more subsequent respiratory cycles at one or more selected from :

i. a manual override maximum pressure set by the operator; ii. a manual override tidal volume set by the operator;

iii. a manual override I: E ratio set by the operator; and

iv. a manual override respiratory rate set by the operator;

53. A method as claimed in claim 52, wherein the method comprises the step of: a. controlling movement of the motor and piston to deliver a predetermined

number of inspiratory cycles at one or more selected from

i. the manual override maximum pressure,

ii. manual override tidal volume, and

iii. manual override respiratory rate set by the operator,

54. A method as claimed in claim 43, wherein the method comprises one or more steps selected from:

c. determining the subsequent I: E ratio of the subsequent respiratory cycle to be delivered to the patient from the subsequent I: E ratio signal; and d. determining the subsequent maximum pressure of the subsequent inspiratory cycle to be delivered to the patient from the subsequent maximum pressure signal.

55. A method as claimed in claim 43, wherein the method comprises the step of

a. setting the subsequent maximum pressure as the threshold maximum

pressure that is not to be exceeded during delivery of the increased subsequent tidal volume.

56. A method as claimed in claim 43, wherein the step of delivering an increased subsequent tidal volume includes the steps of delivering the increased subsequent tidal volume at one or more selected from

a. the determined subsequent respiratory rate;

b. the determined subsequent I: E ratio.

57. A resuscitation device for delivering gas to a patient in respiratory cycles comprising alternating inspiratory and expiratory cycles, said resuscitation device comprising :

d. an accurate positionally controllable motor operatively connected to said

piston to move said piston in said cylinder;

i. the controller being configured for receiving direction from instructions; ii. wherein the instructions are configured for directing the controller to carry out the steps of the method of any one of claims 37 to 56.