TWI889455B - Ventilation system with improved valving - Google Patents

Abstract

A respiratory ventilators system having an inlet configured to be connected to a pressurized air or gas source; an outlet configured to be connected to a patient interface; a valve in-line between the inlet and the outlet; and a control unit configured to control the valve for controlling flow of pressurized air or gas from the source to the patient, wherein the valve includes an air or gas reservoir or accumulator incorporated into the valve body.

Description

Ventilation system with improved valve

The present disclosure relates generally to respiratory care systems and, more particularly, to mechanical ventilation systems or respiratory care systems, i.e., ventilators or respirators. The present disclosure has particular use for, and will be described in connection with, providing respiratory support to human or animal patients whose breathing is impaired by a disease, and may also be used to treat patients suffering from sleep apnea or as a component of an anesthesia system.

The current Covid-19 pandemic has highlighted the need for mechanical ventilation systems for patients with compromised respiratory systems. Respiratory therapy devices can be used to supply clean breathable gas (usually air, with or without supplemental oxygen) to a patient at therapy pressures at appropriate times during the subject's respiratory cycle. Therapy pressure assist can be delivered in a manner synchronized with the patient's breathing to allow for greater pressures during the patient's normal inspiratory cycle and lower pressures during exhalation. Therapy pressure assist can also be delivered to override the patient's normal inspiratory cycle.

A respiratory care system typically includes a gas or air flow generator or a source of compressed gas or air, an air filter, a nasal mask, an oral mask or a full face mask, an air delivery conduit connecting the flow generator to the mask, various sensors, and a microprocessor-based controller. Optionally, instead of a mask, a tracheotomy tube may also be used as a patient interface. The flow generator may include a servo-controlled motor and an impeller forming a blower. In some cases, a brake applied to the blower motor may be implemented to reduce the speed of the blower more quickly, thereby overcoming the inertia of the motor and impeller. Despite the inertia, the brake allows the blower to reach a lower pressure condition more quickly in time to synchronize with the patient's exhalation. In some cases, the airflow generator may also include a valve that can be configured to discharge the generated air into the atmosphere as a means of varying the pressure delivered to the patient, as an alternative to motor speed control. Sensors measure motor speed, mass flow rate, outlet pressure, etc., such as by pressure transducers, etc. Optionally, the device may include a humidifier and/or heater element in the path of the air delivery loop. The controller may include data storage capacity with or without integrated data capture and display capabilities.

Respiratory care systems can be used to treat a number of conditions, such as respiratory insufficiency or failure caused by pulmonary, neuromuscular or musculoskeletal diseases and respiratory control disorders. They can also be used for conditions associated with sleep disordered breathing (SDB) (including mild obstructive sleep apnea (OSA)), allergic upper airway obstruction, or early viral infection of the upper airway.

The current Covid-19 pandemic has stretched the current supply of respiratory care systems. Hospitals are forced to share respiratory care systems, i.e. two patients share a ventilator. Hospitals are also using adapted devices known for obstructive sleep apnea as a poor substitute for known ventilators.

Additionally, current ventilators are complex and expensive devices that require constant monitoring and adjustments and are prone to failure.

The present disclosure provides a simple, low-cost ventilator that overcomes the above and other shortcomings of the current state of the art ventilators.

More specifically, the present disclosure provides a ventilator that has significant advantages over current ventilators in terms of cost, size reduction, weight reduction, power reduction, noise reduction, and reliability. A key to the instantaneous ventilator of the present disclosure is a unique air or gas flow valve that incorporates an air or gas reservoir or accumulator. Incorporating the air or gas reservoir or accumulator into the valve simplifies the construction and cost of the system while providing improved response time, thereby providing better patient support. Known ventilators use proportional solenoid valves (PSOL valves) or turbine-based designs, where the core flow/pressure regulating components are high-cost multi-component products (order price is $1,500 to $2,000). In addition, in practice, static friction on the guide post of the plunger of the known PSOL valve may weaken the sensitivity of the valve, which may cause hysteresis. To overcome the above and other shortcomings of known ventilators, the present disclosure adopts a novel low-cost air or gas valve having an integrated air or gas reservoir or accumulator incorporated into the valve, and the valve is basically composed of five major components and basically one moving part.

In one embodiment, the respiratory ventilator system of the present disclosure includes: an inlet configured to connect to a source of pressurized air or gas; an outlet configured to connect to a patient interface; an inline valve located between the inlet and the outlet; and a control unit configured to control the valve for controlling the flow of pressurized air or gas from the source to the patient, wherein the valve includes an air or gas reservoir or accumulator incorporated into the valve body.

In a preferred embodiment, the valve comprises a valve gate controlled by a linear actuator, preferably a servo mechanism, a mechanical screw drive, or a voice coil drive.

The patient interface may be selected from the group consisting of a mask, a cannula, and a tracheotomy tube, and the pressurized air or gas source may be selected from the group consisting of an air tank, a compressor, an air pump, and a pressurized air line.

The present disclosure also provides a method for assisting breathing of a patient in need thereof, comprising: providing a ventilation system as described above; connecting the ventilation system to a pressurized air source and to a patient interface; initiating air or gas flow to the ventilator system to preload an air or gas reservoir or accumulator, and controlling the flow of gas through the ventilation system by opening and closing a valve.

In another embodiment of the present disclosure, the ventilator system includes a heater and/or a humidifier for conditioning the air or gas.

The valve may open and close in response to the patient's normal breathing cycle, or the valve may open and close to introduce a flow of air or gas to override the patient's normal breathing cycle.

The patient may be a human animal; or a non-human animal.

10: Breathing ventilator system

12: Ventilation controller

14: Pressurized gas source

16: Gas supply pipeline

18: Nasal mask or full face mask

22: Patient

24: Capnography monitor

26: Command input and monitor

28: Valve

30: Air or gas input port

34: Inhalation flow connector

36: Expiratory flow port

38: Expiratory flow valve

40: Valve housing

41: Expiratory flow sensor or respiration sensor

42: Gas supply inlet

44: Gas source outlet

46: Gas storage or storage device

48: Valve gate

50: Valve housing sliding surface

52: Valve housing sealing surface

54: Linear actuator

56: Spring assembly

58: Spring plunger

60: Gasket

70: Pressure sensor

72: Humidification and heating module

Further features and advantages of the present disclosure can be seen from the following description in conjunction with the accompanying drawings, wherein the same component symbols represent the same parts, and wherein FIG. 1 is a schematic diagram of a ventilator system incorporating the present disclosure and being shown as a compact ventilation device connected to a patient; FIG. 2 is a perspective view of a compact ventilation device made according to the present disclosure; and FIG. 3 is a perspective view of a valve component of a compact ventilation device according to a preferred embodiment of the present disclosure. 4 and 5 are cross-sectional functional component diagrams of the valve component of the compact ventilation device according to the present disclosure; FIG. 6 is a diagram showing the moment balance of the valve component of the present disclosure; FIG. 7 is an exploded view of the valve component according to the present disclosure; FIG. 8 is a flow chart illustrating the operation of the compact ventilation device of the present disclosure; and FIG. 9A to FIG. 9C are graphs illustrating the triggering airflow according to the present disclosure.

In the detailed description below, the terms "air" and "gas" and the terms "respirator" and "ventilator", respectively, are used interchangeably.

The respiratory therapy device of the present disclosure provides supplemental air or oxygen to the patient at intermittent time intervals based on the patient's natural tidal breathing cycle or based on a programmed breathing cycle.

Referring to Figures 1 and 2, the respiratory ventilator system 10 includes a ventilation controller 12 connected to a pressurized gas source 14. The pressurized gas source can be a pressurized air or air/oxygen tank, a compressor or air pump as shown, or a pressurized air line. The ventilation controller 12, which will be described in detail below, allows pressurized gas to flow to the patient via a gas supply line at 16, which is fixed to a patient interface, such as a nasal mask or full-face mask 18 worn by the patient 22. Alternatively, the patient interface 18 may include a cannula or tracheotomy tube. Completing the system is a capnography monitor 24, which senses and measures the inhaled and/or exhaled airflow from the patient, as well as a command input and monitor 26. The capnography monitor 24 and command input and monitor 26 are known and do not need to be described further for an understanding of the present disclosure.

Central to the respiratory ventilator system 10 of the present disclosure is a gas or air flow control valve 28 having an integral gas or air reservoir or accumulator as will be described below.

Referring now to FIGS. 3-5 , the gas or airflow control valve 28 includes a valve housing 40 that contains the active components of the gas or airflow control valve 28. A gas supply inlet 42 is shown on the negative x-axis plane, while a gas source outlet 44 is on the positive x-axis plane. In addition, the housing 40 forms a gas reservoir or accumulator 46. The gas supply inlet 42 can interface with a standard hospital _O2 source or any gas source (e.g., a gas tank or compressor).

The valve gate 48 described below with reference to Figures 3 and 4 controls the source flow rate QSource(t) based on its position along the X-axis. The face on the negative Z surface slides along the X-axis on the valve housing sliding surface 50. The distance δ between the valve gate face and the valve housing sealing surface 52 on the positive X-axis of the gate determines the flow resistance by forming a resistance channel between the valve housing sealing surface and the valve gate Y-Z surface on the positive X-axis.

With particular reference to FIGS. 5 and 7 , the gas or air flow control valve 28 includes a valve gate 48 configured to slide along the X-axis of a valve housing sliding surface 50 to set its position along the X-axis. The gas or air flow control valve 28 also includes a linear actuator 54, such as a servo mechanism formed of an electrostrictive material, magnetostrictive material such as PZT or PMN, or a mechanical screw drive of a voice coil actuator or other linear actuator structure. Its length and the resulting gate position are controlled under closed loop control based on the desired source flow rate Q _Source (t) or flow source pressure P _Source (t). The valve gate 48 can also be driven under open loop control.

The negative X-direction preload force is applied to the valve gate 48 assembly by the spring assembly 56.

The set screw drives the valve gate 48 in the X direction, thereby setting the spring assembly preload force and the initial position of the valve gate 48 along the X axis.

The spring plunger 58 provides a preload to the valve gate 48 in the negative Z direction. The purpose is to continuously maintain an airtight seal between the valve gate 48 and the valve housing sliding surface 50.

Gasket 60 maintains an airtight seal between the X-Z surface of the valve housing and the valve gate 48.

Referring again to Figures 1 and 2, the ventilation controller 12 includes an air or gas input port 30, which is connected to a gas or air flow control valve 28. The control valve 28 has an outlet connected to a port, which includes an inspiratory flow connection 34 and an expiratory flow port 36, which is in turn connected to an expiratory flow valve 38. The expiratory flow valve 38 can be vented to atmosphere, or connected to scrubbed _CO2 and recirculated through the gas input port 30. The system also includes an expiratory flow sensor or respiration sensor 41 and a connection to a sensor for triggering the valve 28. The expiratory flow sensor or respiration sensor 41 is used to sense the patient's breathing. The sensors may include air flow sensors, temperature sensors, sound sensors, _CO2 sensors, or motion or strain sensors to detect movement of the patient's chest.

The valve covers surround the X-Z plane of the valve housing, one on the positive Y axis and one on the negative Y axis. These covers form an airtight seal between the valve housing 40 and the atmosphere.

Referring again to Figures 4 to 6, the left side of Figure 4 shows the valve in the closed position, where δ = 0, and the valve flow resistance R _Valve (0) is infinite. Figure 5 shows the valve assembly, where the gate has moved a distance δ in the negative direction along the X-axis. Therefore, the valve resistance is no longer infinite, and gas flows from the reservoir to the gas source outlet, as shown.

The valve flow resistance, R _Valve (δ), is calculated as follows: Source flow, Q _Source (t), is controlled by Equation 3, where: Reservoir pressure, P _Reservoir (t) Outlet pressure, P _Outlet (t) Source flow rate, Q _Source (t) Valve height, H _Valve Valve depth along the Y axis, D _Valve Valve distance from the valve housing sealing surface, δ A _Resistance (δ) = Cross-sectional area of resistance channel = D _Valve δ Equation 1)

Gas dynamic viscosity, η (mass/(distance-time) R _Valve (δ) = exhaust flow resistance through the resistance channel = (8η/π) H _Valve / A _Resistance (δ) ^{2 (} Formula 2)

Then, the source flow rate can be determined by the following relationship: Q _Source (t) = (P _Reservoir (t) - P _Outlet (t)) / R _Valve (δ) (Equation 3)

The gas reservoir area in the valve housing is required because the average source flow rate Q _Source (t) does not exceed the available supply flow rate Q _Supply (t), but the peak flow rate of Q _Source (t) exceeds the available supply flow rate. This difference is made up of the gas stored in the reservoir.

The force and torque balance of the generalized valve gate is shown in Figure 6. The control equations for force balance and torque balance are provided in equations 4 to 12.

P _Reservoir = reservoir pressure θ = valve gate angle W = valve gate width H = valve gate height H _Valve = H/Cosθ Formula 4)

D _Valve = Valve gate depth L ₁ , L ₂ & L ₃ = Spring distance c _Friction = Wedge friction coefficient Z _Actuator = Actuator distance from Z=0 P _Reservoir = Reservoir gas pressure F _PressureX = Force from chamber pressure in X direction = -P _Reservoir HD Equation 5)

F _PressureZ = Force from chamber pressure in Z direction = -P _Reservoir (WD + H tan θ D/2) Equation 6)

P_Reservoir(Z/H) 式7) F _Plunger = Force from the spring plunger in the Z direction P _Resistor (Z) = Pressure along the flow barrier

P _Reservoir (Z/H) Formula 7)

F _PResistor = Pressure generated by flow acting on the barrier = (P _Reservoir /2) D _Valve H _Valve Formula 8)

F _Spring = Force provided by preload spring F _Actuator = Force provided by positioning actuator Z Force balance F _Z = F _Plunger + F _{Pressure Z} + 3 F _Spring Sin θ Equation 9)

F _Friction = Friction in X direction = F _Z c _Friction Formula 10)

X force balance (3 F _Spring + F _PResistor ) Cos θ = F _PressureX + F _Actuator Formula 11)

The moment balance about the Y axis is: F _Spring (L ₁ +L ₂ +L ₃ )Cos θ ² +F _PResistor ((2/3)H/Cos θ)Cos θ ² =F _PressureX H/2+F _Actuator Z _Actuator Formula 12)

Referring also to FIG. 7 , the valve assembly 28 controls the flow of source gas by varying the flow resistance R _Valve (δ). This is accomplished by varying the length of the actuator 54 ( FIG. 5 ) ΔX, which in turn causes the valve gate 48 to move δ along the X axis in a corresponding gap between the valve gate 48 and the valve housing sealing surface 52. The reservoir pressure P _Reservoir (t) is monitored by the pressure sensor 70 ( FIG. 1 ) and utilized to calculate the required ΔX command, which controls Q _Source (t), as summarized in Equation 3.

Gas flows through an in-line flow sensor in the gas supply inlet 42 to measure the source flow Q _Source (t) as a function of time t. This flow measurement is used by the gas source controller and sensor/user interface to calculate the required ΔX command, which controls Q _Source (t) as summarized in Equation 3.

As with the conventional ventilator, the inlet gas or flow may require humidification and/or heating. This is accomplished by commands from the controller to the humidification and heating module 72 which is in communication with the reservoir 46 which adds water vapor to add humidity to the airflow by heating and subsequent evaporation of the water, piezoelectric atomization of the water, or other conventional methods of adding water to the airflow. The gas may also be heated by the module as it flows through the module.

The gas flows through the relative humidity sensor, which measures the relative humidity of the gas, RH(t), as a function of time t. This measurement is used by the controller to generate the required RH _Command (t), which is a function of time.

The temperature and pressure source module measures the gas temperature T(t). The controller and sensor/user interface use this temperature measurement to calculate the heating command T _Command (t) to the humidification and heating module to control the gas temperature.

The temperature and pressure source module can also measure the gas outlet pressure P _Outlet (t). This pressure is used by the controller and sensor/user interface to calculate the required ΔX command, which controls Q _Source (t) as summarized in Equation 3. The outlet of the temperature and pressure module interfaces with a gas supply line that terminates in a pressurized nasal ventilator or other patient breathing device, such as a mask, cannula, or tube.

The gas source controller and sensor/user interface includes the sensor interfaces required to control the gas source flow rate Q _Source (t), pressure P _Outlet (t), temperature T(t) and relative humidity RH(t). It generates actuator commands △X(t), temperature commands T _Command (t) and relative humidity commands RH _Command (t). It also interfaces with the user command input device and status monitor to receive the user-defined command set: gas source flow rate Q _Source (t), pressure P _Outlet (t), T(t) and RH(t). The gas source controller and sensor/user interface also provides sensor readings to the user command input device and status monitor.

The user command input device and status monitor allows the user to generate commands for: gas source flow rate Q _Source (t), pressure P _Outlet (t), T(t) and RH(t). It also displays sensor readings. The device can be an I-Pad type interface that communicates with the pressurized nasal respirator assembly either wired or wirelessly.

The gas supply line can be a standard _O2 line. The gas supply line can also be insulated to minimize gas heat loss when traveling from the gas source to the pressurized nasal ventilator assembly. The gas supply line can also incorporate an electric heating element to maintain the gas temperature, and can also incorporate a power and data line set to provide power to the pressurized nasal ventilator assembly and receive sensor data from the pressurized nasal ventilator assembly. Because the gas supply line has a known flow resistance _RGSL , the pressure _PSource (t) at the entrance point of the pressurized nasal ventilator air port can be calculated by knowing _QSource (t), _POutlet (t) and _RGSL by the formula _PSource (t)= _POutlet (t) _-QSource (t) _RGSL .

Additional sensors may provide inputs for controlling the gas source assembly. These include, but are not limited to, chamber pressure P _Chamber (t), chamber temperature T _AC , chamber relative humidity RH _AC , ETCO ₂ and/or O ₂ measurements sampled from the chamber of a pressurized nasal ventilator assembly, impedance-based devices that monitor respiratory rate and tidal volume via chest movement (e.g., systems).

Referring to FIG. 8 , the overall operation is as follows: the gas source 14 supplies pressurized gas to the ventilation controller 12, and the ventilation controller 12 opens the valve 28 to supply gas to the patient 22 at the required frequency, flow rate and pressure to support the patient's breathing. Since there is pressurized gas or air supply in the air or gas reservoir 46 incorporated into the valve 28, the delivery of pressurized air or gas to the patient 22 is basically carried out at the same time as the valve is opened. The air or gas reservoir 46 is refilled when the patient exhales.

Compared to known ventilation devices, the resulting ventilator system of the present disclosure is a low-cost, relatively simple device that is rugged, small and lightweight, and exceptionally fast in responding to patient needs.

Figures 9A to 9C show the flow and pressure waveforms of the patient at three rising times (pressure support).

10: Breathing ventilator system

12: Ventilation controller

Claims (5)

A respiratory ventilator system, comprising: A pressurized air or gas source; and A valve system, the valve system comprising a first valve and a second valve, the first valve and the second valve are connected in series with each other and configured to control the flow of pressurized air or gas from the pressurized air or gas source to a patient; wherein the first valve comprises: An inlet and an outlet, the inlet of the first valve is configured to be connected to a pressurized air or gas source, and the outlet of the first valve is connected to an inlet of the second valve; wherein the second valve comprises an inlet and an outlet, the inlet of the second valve is connected to the outlet of the first valve, and the outlet of the second valve is configured to be connected to a patient interface; wherein the first valve and the second valve act together to form a chamber in the form of an air or gas reservoir incorporated into a body of the valve system and configured to store a quantity of pressurized air or gas, wherein the air or gas reservoir is configured to open when the first valve and the second valve are opened and to mix the stored quantity of pressurized air or gas with pressurized air or gas from the source The invention relates to a method for delivering a pressurized air or gas to a patient together with a second valve, thereby increasing a peak flow rate of the air or gas delivered to the patient, wherein the air or gas reservoir or accumulator is configured to be filled with a pressurized air or gas reservoir when the valve for controlling the flow of pressurized air or gas delivered to the patient is closed, so that the flow of air or gas through the second valve exceeds an available supply flow rate of the pressurized air or gas source. A breathing ventilator system as described in claim 1, wherein the second valve includes a valve gate controlled by a linear drive mechanism, the linear drive mechanism including a mechanical screw drive or a voice coil drive. A respiratory ventilator system as described in claim 1, wherein the patient interface is selected from the group consisting of a mask, a tube and a tracheotomy tube. A breathing ventilator system as described in claim 1, wherein the pressurized air or gas source is selected from the group consisting of an air tank, a compressor, an air pump and a pressurized air pipeline. The respiratory ventilator system as described in claim 1 further includes at least one of a heater and a humidifier for conditioning the air or gas.