GB2390306A

GB2390306A - A patient ventilating apparatus with domed bellow chamber

Info

Publication number: GB2390306A
Application number: GB0306365A
Authority: GB
Inventors: Paul Magellan Fenton
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-07-03
Filing date: 2003-03-20
Publication date: 2004-01-07
Also published as: GB0215330D0; GB0306365D0

Abstract

A ventilator for inflating a patients lung comprising a dome 2, with a handle 9, mounted on a flexible support such as bellows or concentric rings 3 with a second bellows 10 and spring 11 mounted inside the dome connected to a pneumatic control unit (30, Fig 3), such that intermittent positive pressure ventilation can be administered to a patient either by passing compressed air from the pneumatic control to the interior of the dome to depress the internal bellows or else manually moving the dome up and down on the flexible support. The device can be used to ventilate a patient both in the conventional manner by compressing a bellows mounted inside a dome as well as at the beginning or end of mechanical ventilation or in case of failure of the compressed gas supply, by manually elevating and depressing the dome.

Description

A patient ventilating apparatus Description

The invention relates to an apparatus for the ventilation of a patient (mechanical ventilation of the lungs).

Anaesthesia or resuscitation breathing apparatus is used to provide anaesthetic gas or oxygen to a patient during a surgical procedure or during a period of respiratory insufficiency. Anaesthetic gas means a respirable gas containing an inhalation anaesthetic vapour with oxygen enrichment.

In the course of an operation a patient may breathe spontaneously or have respiration assisted 2 manually by an anaesthetist or by a mechanical ventilator. The latter two methods are also called intermittent positive pressure ventilation (1.P.P.V.) to distinguish this mode from the negative pressure created during spontaneous (normal) ventilation. When a mechanical ventilator is incorporated in a breathing system, the patient may breathe spontaneously through the system 6 (ventilator switched off) or receive ventilatory support, which is then called controlled or mechanical ventilation. Controlled ventilation may be required during or after many surgical procedures according to the patient's condition, the type of operation being performed or during a period of resuscitation.

One type of breathing system for anaesthesia, known as the draw over system, is particularly suited for use in developing countries where bottles of compressed anaesthetic gas may not be available. In the drawover system, ambient air with or without oxygen enrichment may be 2 drawn through a liquid anaesthetic agent vaporizing device, called a vaporizer, by negative pressure created by the patient's inspiratory effort. The oxygen enrichment may be provided by an oxygen concentrator, an electrical device that extracts oxygen from room air. The resultant anaesthetic gas enters the patient's lungs via a non-rebreathing, inflainmg valve, the exhaled gas 2e being vented to atmosphere via the same valve.

In another configuration, called the circle system, pressurized anaesthetic gas is controlled by a flow device called a rotameter and then passes through a different type of vaporizer into a recirculating breathing system. The patient may breathe spontaneously or receive I.P.P. V. from a mechanical ventilator incorporated in the system. Most exhaled gas is re-circulated after absorption of carbon dioxide in a soda lime absorber and is not discharged direct to atmosphere.

Despite being of great utility the draw-over system has several disadvantages: discharge of the x expired gas is wasteful of oxygen and anaesthetic agent, the anaesthetic gas is an environmental pollutant and may be toxic to members of the operating theatre team. Scavenging and disposal of waste gas from the non-rebreathing valve is difficult since it is required to be located close to the patient's airway. The valve is relatively large and it may thus be inconvenient, concealed from 2 the anaesthetist by surgical drapes or its weight may cause a tracheal breathing tube to be pulled out. The inflating function of the valve makes it possible to become jammed with consequent pressure damage to the patient's lungs. Few mechanical ventilators are currently available for use with draw-over systems which further limits their use.

The circle system, being less polluting and more economical, is the most widely used anaesthesia system but it depends upon a bottled compressed anaesthetic gas and oxygen supply.

Many types of mechanical ventilator are available for circle systems but Hey all have a no requirement for compressed driving gas, and usually electricity, in order to function. Most commonly, the design of ventilator has a transparent rigid dome with an oscillating bellows inside, the movement of which displaces gas from the ventilator and inflates the patients lungs.

This type has no facility for manual operation and cannot function in the event of power or gas failure. 2s The present invention seeks to provide an improved anaesthesia and respiratory support system being a design for a mechanical ventilator suitable for use with circle, draw-over or other patient breathing system. It is powered by compressed air from the electrically-driven compressor of an oxygen concentrator, Me latter configured with a separate air pipeline, and is independent of

-3 bottled compressed gas supplies. The aforementioned dome-and-bellows concept is retained but the anaesthetist may ventilate the patient by hand in the event of electrical or mechanical failure or for resuscitation or any emergency by manually raising the dome, which is mounted on a bellows, to draw room air into the system and depressing it to ventilate the patients lungs.

s It will be appreciated that the ventilator may be used in the course of anaesthesia or in other circumstances where respiratory support is needed for a patient, such as post-operatively or in resuscitation. lo According to a first aspect of the present invention, there is provided a rigid dome with a gas tight attachment at its base to a bellows skirt made from a flexible material such as rubber, the two forming a single chamber arranged with a patient breathing system to allow gas from that system to be drawn into and forced out of the chamber by movement of the dome on the flexible bellows. It will be appreciated that the dome may be cylindrical, ovoid or spheroid in shape and that the flexible support may be configured with concentric rings instead of a bellows.

The lower edge of the bellows skirt has a gas tight attachment to the base plate of a rigid ventilator housing. Inlet and outlet valves permit entry and exit of gas to and from the above chamber and direct one way flow in the breathing system. It will be appreciated that these ports 20 may have other configurations, such as a single port with to-and-fro connections to the breathing system, may be located outside the ventilator and may also connect to a draw over, or other type of breathing system. The gas may be oxygen-enriched anaesthetic gas provided by an oxygen concentrator or cylinder, though it will be appreciated that the present invention can be used for patient ventilation with any respirable gas including room air.

According to a second aspect of the present invention the dome has a device located on its outside, which may be a knob, handle or recess, to enable the hand of the anaesthetist to grasp and lift the dome up on the flexible bellows skirt and thus draw gas into the chamber.

- According to a third aspect of the present invention, a second smaller bellows also made of flexible material, called the internal bellows, may be mounted on a flange within the dome in a gas tight manner such that the patient's respirab]e gas from the chamber can freely enter the interior of this bellows but cannot enter the space between the bellows and dome.

s According to a fourth aspect of the present invention a large diameter light spring is located inside the internal bellows, its lower end rests on the flange inside the dome and its upper end urges against a plate fixed to, or integral with, the top of the bellows thus maintaining the latter in an upper position against the underside of the dome when the spring is extended. The dome lo may be transparent so that the movement of this bellows is visible.

According to a fifth aspect of the present invention, a flexible pipe may perforate the rigid base, pass through the chamber and open into the space between the internal bellows and dome by perforating the flange. The tube may be configured loosely or have corrugated walls so as to s allow unhindered movement of the dome on the skirt and be connected to a source of non respirable driving gas, such as from a cycling pneumatic ventilator control device driven by compressed air from an oxygen concentrator, this compressed air being isolated from the respirable gas in the cha:nber. An increase in pressure from this driving gas source may cause the air to be forced through the flexible pipe into the above space. The bellows is thereby forced 20 down within the dome against the spring and causes the volume of the chamber to be reduced.

Respirable gas in the chamber may thereby be forced through the outlet port into a patient breathing system to ventilate a patient.

According to a sixth aspect of the present invention, three or more recesses or grooves may be as provided at the lower outside edge of the dome which engage with the same number of spring loaded ball bearings on the ventilator housing in order to retain the dome in the upper position.

Negative pressure from within the dome or manual pressure on the top of the dome may overcome the retaining force of the spring loaded balls and cause the dome to descend, to be then supported only by the flexible skirt. Changes in pressure within the chamber, for example

caused by the spontaneous breathing of a patient, may cause movement of the dome, which effect serves as a monitor of respiration. It will be appreciated that the dome may be retained in the upper position by a different means such as by magnets instead of roller bearings.

s During the inspiratory phase of controlled ventilation, the inner bellows is forced down by cycled gas entering the space between the bellows and dome. The reactive force on the dome resulting from increased positive pressure in the chamber due to lung inflation may cause the dome to be forced into the upper position and be retained there by the roller bearings.

o The ventilator allows three functions during patient respiration as follows. 1. Free flow of respirable gas through the ventilator and unidirectional valves allows the patient to breathe spontaneously. 2. The anaesthetist may administer l.P.P.V. to the patient by elevating and depressing the dome using the knob or handle. 3. Mechanical ventilation may be started by turning on the pneumatic ventilator control. This cycles compressed air into the space between the dome and the internal bellows. The internal bellows is forced down displacing the gas in the dome into the breathing system, thereby administering I.P.P.V. to the patient.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings 1 to 8 in which: Figure l is a sectional view of a first embodiment of a patient ventilating apparatus according to the present invention, with the dome and internal bellows in the upper position.

Figure 2 is a sectional view of a second embodiment of a patient ventilating apparatus, 25 according to the present invention, connected with a circle type of patient breathing system with a single to- and frobreathing pipe to the system. Figure 2a. shows a connection with a draw over type of patient breathing system.

Figure 3 is a schematic plan view of a third embodiment of a patient ventilating apparatus,

- according to the present invention, connected to a c*cle type breathing system. The example shows an oxygen concentrator providing both compressed gas to a pneumatic cycling ventilator control which controls gas flow to the ventilator as well as oxygen via a rotameter and vaporizer into a breathing system using a second pipeline.

s Figure 4 is as Figure I but with the internal bellows depressed against the spring during the inspiratory phase of mechanical administered I.P.P. V.

Figure 5 is as Figure 1 but with the dome depressed against the bellows skirt during a manually lo applied positive pressure ventilation with the internal bellows in the upper position.

Figure 6 is a schematic view of an embodiment of the dome viewed from below and Figure 6a shows an enlargement of the configuration of the groove for the spring roller ball, the lower end of the internal bellows? upper end of the skirt bellows, spring support flange and driving gas inlet. Figure 7 is a perspective view of embodiments shown in Figs 2 and 3.

Figure 8 is a sectional view of a fourth embodiment showing a hemispherical dome and internal To bellows for a patient ventilating apparatus according to the present invention.

Referring to Figures I and 2, embodiments of a patient ventilating apparatus (1) are arranged with a rigid transparent dome (2) on a flexible bellows skirt (3) forming a single gas tight 25 chamber inside a housing (4) such that free movement of the dome on the skirt will allow the user (anaesthetist) to move the dome and thereby draw gas into or force it out of the chamber via a patient breathing system (19, 25), with one way valves to direct flow (id 6, 7 and 8). Such valves are configured according to the type of patient breathing system. A knob (9) allows manual elevation of the dome.

-7 The arrangement also allows a patient (P) to breathe spontaneously through the apparatus or to receive manually assisted 1.P.P.V. from an attending anaesthetist by the repeated action of elevating and pressing down on the dome.

Inside the dome, an internal bellows ( l O) with spring ( 1 l inside it is mounted on a flange ( 12) which is fixed to the dome (2) such that these four components move as one unit on the bellows skirt (3). The top of the spring (11) urges against a plate (13) in the internal bellows (10) and maintains the top of the latter pressed against the underside of the dome (2).

A flexible or corrugated pipe (14) passes through the chamber inside the skirt (3) perforating at its lower end (16) the base of the housing (4) and having its upper end connected in a gas tight manner with a hole ( 15) in the flange ( 12) located between the internal bellows (10) and the dome (2). The pipe ( 14) is coiled loosely so that its rigidity cannot impede free movement of the 15 dome. A source (17) of compressed gas cycled for inspiration and expiration from a ventilator control unit is connected to the inlet (16) and pipe (14) and thereby increases pressure in the space between the dome (2) and internal bellows (l 0) during the inspiratory phase of 1.P.P.V. This 20 causes the internal bellows to be forced down against the spring (11), reducing the volume of the dome and skirt chamber (3) and thus displacing the respirable gas in the chamber towards the patient (P) resulting in inflation of the lungs. During the expiratory phase, the pressure in the flexible pipe (14) falls to atmospheric and the spring ( l 1) returns the internal bellows (10) to the upper position, at the same time drawing fresh respirable gas into the chamber from the patient as breathing system, according to the direction of the one way valves (5,6,7,8). An airway pressure gauge (l 8) shows the pressure in the chamber.

The present invention which composes the rigid transparent dome with knob, bellows skirt, internal bellows with spring, perforating flexible pipe and ventilator housing may be connected

-8 with a circle type patient breathing system (19) with soda lime carbon dioxide absorber (20) reservoir bag (21) pressure relief valve (22), fresh gas source (23) and balloon type or other type of expiratory valve (24) or may be connected with a draw-over system (25) with patient inflating valve (8) or another type of patient breathing system.

A draw-over type vaporiser (26) open to room air may be connected as a reserve vaporiser to allow anaesthetic vapour and/or air to enter the system in case the fresh gas source (23) fails.

Referring to Figure 3, an embodiment of an apparatus (1) for ventilating a patient (P) is arranged with an oxygen concentrator being a source of compressed oxygen and air (27) to supply a lo rotameter (28) and vaporizer (29) as well as a cycling ventilator control device (30). The pipe (17) supplies compressed gas to the flexible pipe (14) in the ventilator (1). The pipe (31) operates the balloon occluding valve (24).

Referring to Figure 4, the internal bellows (10) is shown forced down against the spring (11) by 5 the cycled compressed gas in the flexible pipe (143 thereby reducing the volume of respirable gas in the dome and skirt chamber (3) and displacing this gas towards the patient, resulting in inflation of the lungs. The consequent rise in airway pressure causes a reactive upward force on the dome (2) pushing it to the upper position, overcoming the roller bearings (32) which may retain it in this position.

Referring to Figure S. the dome (2) is shown in the lower position disengaged from the roller bearings (32) at the end of a manually assisted inflation of the lungs with the cycling pneumatic ventilator control switched off. The skirt bellows (3) is compressed with reduced volume in the skirt chamber as in Figure 4, but the internal bellows (10) and spring (11) are in the upper 25 position. The flexible pipe (14) lies coiled in the base of the ventilator housing (4).

Referring to Figure 6, the dome (2) is seen from underneath looking into the internal bellows (10.

-9- Figure 6a shows the configuration of the f ange ( 12), lower end of the dome (2) and internal bellows (10), roller bearings (32) and notch for roller bearings, flexible pipe (14) and orifice (15). 5 Referring to Figure 7, the ventilator may be located on the work surface of an anaesthesia work station with the cycling pneumatic ventilator control unit mounted above, underneath a top shelf or the control unit and ventilator may be used free standing on any bed side trolley.

Referring to Figure 8, a hemispherical dome is shown operating on the same principles.

2s

Claims

1. A patient ventilating apparatus for mechanical ventilation of the lungs comprising a hollow s donate mounted on a flexible support, the two conning a single chamber for containment of respirable gas where the dome moves on the support during the respiratory cycle.

2. A ventilator as in claim 1 where the flexible dome support comprises a bellows.

lo

3. A ventilator as in claim 1 where the flexible dome support comprises a series of concentric rings or pistons.

4. A ventilator as in claim 1 where the dome is transparent.

1 s S. A ventilator as in all previous claims which when connected with a patient breathing system allows intermittent positive pressure ventilation (I.P.P.V.) of a patient's lungs by means of manual elevation and depression of the dome' the latter moving on the support.

6. A ventilator as in all previous claims having a device such as a knob, handle or recess on, no or set in the surface of the dome to enable the user to grasp and raise the dome and thereby to draw anaesthetic gas, oxygen or other respirable gas into the space inside the dome and support. 7 A ventilator as in all previous claims provided with an internal flexible bellows on a 25 mounting fixed inside the dome.

8 A ventilator as in all previous claims provided with a spring to maintain the said internal bellows in an extended position inside the dome.

9 A ventilator as in all previous claims where the said internal bellows and spring can be depressed by the force of a cyclically operating compressed driving gas to provide the inspiratory phase of intermittent positive pressure ventilation (I.P.P.V.) to a patient, such pressurised gas being delivered by a pipe into the space between the internal bellows and 5 the dome.

10 A ventilator as in all previous claims where the movable dome may be retained in an upper position by the action of spring loaded bearings or magnets mounted on the ventilator housing. 11 A ventilator as in previous claims provided with a gas tight liner inside the concentric rings or pistons to prevent leakage of gas.

12 A patient ventilator substantially as described herein with reference to Figs 1-8 of the s accompanying drawings.