WO1986004822A1

WO1986004822A1 - A device in artificial respiration- and/or anaesthetic systems

Info

Publication number: WO1986004822A1
Application number: PCT/SE1986/000072
Authority: WO
Inventors: Lars Jonsson
Original assignee: Lars Jonsson
Priority date: 1985-02-20
Filing date: 1986-02-20
Publication date: 1986-08-28
Also published as: SE8500817D0; JPS62501892A; AU5544086A

Abstract

A device in artificial respiration- and/or anaesthetic systems comprising: a first conduit (2) extending from an inhalation member (1) connectible to the patient, said first conduit being arranged for the supply of gas from a gas source; a second conduit (4) for removal of exhalated gas; a flexible container (3) arranged in said first container (1) at some distance from the inhalation member (1); and a stop valve (6) arranged in said second conduit (4) at some distance from the inhalation member (1), said valve (6) being arranged to close by means of a membrane (27) or the like by the action of pressurized gas from the system. The stop valve (6) comprises a second manually adjustable control valve (16), which in a first end position is arranged to provide a flow communication (24, 25, 26) between the pressure face of the membrane (27) and the pressurized gas, and in a second position is arranged to shut off the supply of gas and open a communication passage (28, 29) between the pressure face of the membrane and the atmosphere.

Description

A DEVICE IN ARTIFICIAL RESPIRATION- AND/OR ANAESTHETIC SYSTEMS

The present invention refers to a device in a device in artificial respiration- and/or anaesthetic systems comprising: a first conduit extending from an inhalation member connectible to the patient, said first conduit being arranged for the supply of gas from a gas source; a second conduit for removal of exhalted gas; a flexible container arranged in said first container at some distance from the inhalation member; and a stop valve arranged in said second conduit at some distance from the inhalation member said valve being arranged to close by means of a membrane or the like by the action of pressurized gas from the system.

BACKGROUND OF THE INVENTION

Anaesthetic systems of the type available today can be divided in closed systems and in semi-closed systems. In closed systems the contents of oxygen and carbon dioxide in the supplied gas are controlled by removing carbon dioxide from the expiration- gas and supplying oxygen thereto, after which the gas is re-used. These systems are very complicated and are not fruther discussed here. Semi-closed systems are characterized by the facts that expirated gas is removed through a channel system with an outwards open container, usually in the form of a relatively long tube or the like with one end open and one closed and to which the expirated gas is supplied at the same time as an evacuation device all the time ventilates off gas at a flow somewhat exceeding the avarage flow for the gas supplied to the container and gives it off to an evacuation channel or the like. Due to the fact that the system in this way is "semi-closed" it provides the advantages of avoiding discharge of gas in the operating- room and that the discharge from the systen takes place very close to atmospheric pressure.

Previously known semi-closed systems of the type Mapleson A (see Brit ,ish Journal of Anaesthesia, 1968, 40, p. 666-674, " ebreathing Circuits" , by M.K. Sykes) are only intended for spontaneous breathing, at which gas is supplied to the patient through the supply conduit at the inspiration, and when the patient starts to expirate the first amount of expirated gas will return through the supply conduit, the flexible reservoir of which receives a certain amount of gas under pressure rise, until the non-return valve in the return conduit opens at its predetermined pressure, after which the rest of the expirated gas escapes through the return conduit and the non-return valve. When the patient takes a new breath the non-return valve will close and inspiration takes place through the supply conduit. The advantage of this construction is that on one hand rebreathing of used gas will not occur, which would lead to i.a. an increase of the carbon dioxide content, but on the other hand avoids that unused gas is discharged. The gas initially expirated by the patient has never reached the lungs but only the so called dead space in the air-passages. These semi-closed systems intended for spontaneous ventilation involve at the intended use a good economy of the anaesthetic gas in combination with an insignificant rebreathing of used gas .

The problems of gas economy mentioned here are related to the size of the "dead space" , which is the amount of inspirated gas which uninfluenced is expirated in each breath. This volume amounts to about 150 ml for an adult and can make 30 7. of a normal breath. This volume could be reused and should not then be mixed with the gas actually used, i.e. such gas that has been in contact with the gas-exchanging tissues of the lungs. With respect to spontaneous breathing this problem is solved by the mentioned, known system.

Only spontaneous ventilation has been mentioned, i.e. when the patient himself takes a breath and breathes it out again. However at narcosis also so called pressure ventilation or controlled ventilation takes place, at which inspiration is made under pressure. During the inspiration phase an overpressure is created and it must be made sure that the expiratory valve is closed. Expiration is made when the pressure ceases through the "innerent resiliency" of the patient. It would also be possible to modify the known systems so that the expiratory valve can close at the same time as the bag is manually compressed. However a considerable amount of the used gas from the expiration will reach the supply conduit, due to the re-filling of the bag, which will lead to cosiderable rebreathing and increased carbon dioxide content. The alternative is to considerably increase the supply of gas, at which however the gas consumption is increased due to the fact that the unused gas which initially comes out at the expiration can not be utilized.

From practical point of view it is desired that a change between spontaneous and controlled ventilation can be done. It is e.g. desired that the actual anaesthetizing at an operation is made with spontaneous vetnilation, since a conscious patient feels pressure ventilation as very unpleasant, after which one gradually changes to controlled ventilation during the operation, in order to have the patient under safe control, and finishes with spontaneous ventilation during the awakening phase, when the anaesthesia is ceased and air is supplied, at which for safety reasons one shil will have the possibility to resort to controlled ventilation at any time if the patient breathes weakly.

In SE-B-389.966 is shown a valve intended for closed systems for narcosis or artificial respiration. The valve is arranged in a tube circuit comprising a flexible bag, an inhalation member, a CO -absorber and a pipe socket, through which fresh anaesthetic gas can be supplied, at which the valve is placed between the tube socket and the flexible bag. The valve has double seats and a spring-loaded valve plate moveable therebetween. The valve is adjustable between intermittent operation and other operation, at which the valve opens at a predetermined pressure and permits the gas to leave the circuit. At intermittent operation a strong pressure increase in the system, e.g. when the anaesthetist assistant compresses the bag, will cause the valve plate to be pressed to bear against the upper seat and close the valve. When the pressure *1 on the bag is ceased the pressure in the system is decreased, at which the valve will move towards the lower seat, but as soon as the patient expirates an amount of air the plate will lift from the seat and open the valve.

At spontaneous breathing the valve can be switched over so that the valve plate can not be lifted more than to a position between the seats, at which it is prevented that the valve closes e.g. when the patient coughs.

In SE-B-437.936 (published on Feb. 26, 1985 after the priority date of the present application and corresponding to WO 85/00983) is disclosed a valve device in anaesthetic systems for controlled discharge of used gas. The valve comprises a sensing means in the form of a constriction with side passages on either sides thereof, said passages communicating with a pair of chambers arranged on opposite sides of a membrane. The pressure difference created in the sensing means at the gas flow should control the valve, so that it opens when the gas flow in a certain direction exceeds a certain value. The condition for this valve to function in the desired manner is that the different volumes and flow areas involved must be exactly adapted to each other. With regard to the big individual differences in expiration flow between different patients, it would be almost impossible to match the balance between the forces actuating the membrane, so that the valve always opens in the correct moment.

Other systmes for controlled ventilation are known per se, which however suffer from other drawbacks, such as deficient ability to function at spontaneous ventilation. This problem is sometimes solved by using two systems with a face mask each, which are changed.

0B.JECT OF THE INVENTON

The object of the invention is to provide a respiratiπg- and anaesthetic device which fulfils very high demands on function, reliability, simlicity and clinical applicability and which eliminates the drawbacks, which the previously known systems suffer from, and which maintains the advantages of known "semi-closed" systems of the type Mapleson A at spontaneous ventilation, but which also can be used at controlled, so called pressure ventilation, when the gas supply to the patient takes place by force, either manually by compressing a bag or the like, or by connected mechanical means, e.g. a respriator.

These objects have been fulfiled by the fact that that the stop valve comprises a second manually adjustable control valve, which in a first end position is arranged to provide a flow communication between the pressure face of the membrane and the pressurized gas, and in a second position is arranged to shut off the supply of gas and open a communication passage between the pressure face of the membrane and the atmosphere.

By this a simple and very reliable construction is provided, which only requires a manual switching at a change from spontaneous to controlled ventilation and vice versa. It is further provided that the pressure increase in the supply conduit created during the filling phase at controlled inspiration results in that the stop valve at the discharge conduit will be closed and thereafter will operate in the usual way as for spontaneous ventilation systems, when the patient expirates, i.e. initially during a short phase gas returns to the supply chamber when the valve is closed, after which this is opened when the expiratory pressure has increased to the adjusted opening pressure. In order to achieve the desired function it is further necessary that the flexible reservoir is mounted in the supply conduit, which shall receive the initial unused expiratory gas.

DESCRIPTION OF THE DRAWINGS

The invention will now be closer described with reference to the drawings, which show some embodiments.

Figs. 1-3 show schematically a partial rebreathing system according to the invention at spontaneous ventilation, at which fig. 1 shows the inspiration phase, ig. 2 the respiration-, filling phase and fig. 3 the respiration-, discharge phase.

Figs. 4-6 are analogous views with figs. 1-3 showing controlled or assisted ventilation, where fig. 4 shows the inspiration phase, fig. 5 the expiration- filling phase and fig. 6 the expiration- discharge phase.

Figs. 7-9 are also analogous views with figs. 1-3 of a partial rebreathing system at controlled ventilation with respiratior or the like, at which fig. 7 shows the inspiration phase, fig. 8 the expiration-, filling phase and fig. 9 the expiration- discharge phase.

Fig. 10 shows on a larger scale- above natural size- a section through the valve device according to the invention, and

Fig. 11 shows a section through a modified valve device according to the invention.

DESCRIPTION OF THE EMBODIMENTS

The respirating system according to the invention comprises in a known manner an inhalation member 1 , e.g. a face mask or a tracheal tube, a supply conduit 2 connected to a gas source (not shown) and provided with a flexible container 3 e.g. in the form of a rubber bag, and a discharge conduit 4 connected to a valve means 5. The flexible container 3 is connected to a supply chamber 6 in which is arranged an ejector 7, through which breathing gas is supplied to the system through the conduit 8.

The valve means 5, which is shown more in detail in fig. 10 and 11 , consists of two main portions, a nonreturn valve 9 comprising a housing 10 with inlet opening 11 to the discharge conduit 4 and an outlet opening 12 to an evacuation conduit 13 and a valve plate 14, which in its neutral position rests against a seat 15. The other portion of the valve means 5 consists of a control valve 16, the valve body 17 of which .is displaceable between two valve seats 18 and 19 by means of a screw spindle 20 and knob 21. In one lower end position of the valve body 17 a flow passage is established from an opening 22, to which a control conduit 23 is connected, by way of the passages 24,25 and 26 to the upper side of a membrane 27 to which said valve plate 14 is attached. In the lower end position of the valve body 17 shown in fig. 10 the communication with the atmosphere through the passages 28 and 29 is blocked.

o If the knob 21 is rotated about 90 the valve body 17 will be displaced to its other, upper end position to bear against the valve seat 19, at which the flow passage from the control conduit 23 to the space above the membrane 27 is closed, while the space above the membrane 27 is brought to communicate with the atmosphere through the passages 26,25,29 and 28, so that the same pressure acts on both sides of the membrane .

The end 30 of the control conduit 23 remote from the valve means 5 is connected to the suction side 31 of the ejector 7. The ejector 7 is designed such that the gas pressure in the conduit 8 is so measured that at continuous supply of breathing gas to the system the supplied gas amount is somewhat smaller than the amount corresponding to one breath per time unit. The valve means is further so designed that when there is no overpressure acting upon the membrane 27, the valve plate 14 of the nonreturn valve 9 is brought against its valve seat 15 so that the valve is closed, but opens at a predetermined pressure, so that at spontaneous breathing the valve is opened when the pressure reaches said limit.

FUNCTIONAL DESCRIPTION

At spontaneous breathing the patient will during the inspiration phase- see fig. 1 - inspirate gas, which is in the supply conduit 2, the supply chamber 6 and the flexible container 3, which more or less is emptied of its content, at the same time as a certain amount of fresh breathing gas continously is supplied to the system. The nonreturn valve 9 is closed and the gas volume in the discharge conduit 4 remains uninfluenced.

During the initial phase of expiration, illustrated in fig. 2, the gas from the patent's so called "dead space" , i.e. from the upper parts of the air-passages, will fill the flexible container 3 , when this shows a lower pressure than the rest of the system and when the pressure in the supply conduit 2 and the discharge conduit 4 are equal the nonreturn valve 9 will open at continued expiration, as is shown in fig. 3, so that alveolar gas, i.e. used breathing gas, can be supplied to an evacuation conduit 13.

If the spontaneous breathing of the patient is insufficient or if it would cease the knob 21 of the valve means 5 is switched from position S ( ^spontaneous ) to position K ( =controlled ) by rotating it about 90 , at which the valve body 17 is displaced from its upper to its lower end position. Spontaneous breathing has then been changed into controlled or assisted breathing, which means that the anaesthetic operator either manually compresses the resilient container 3, as is shoen in ig. 4, or connects a respiratior, as is shown in figs. 7-9. A compression of the resilient container 3 results in that the gas in it is pressed into the supply chamber 6 and the conduit 2 and which pressure increase propagates through the control conduit 23 which presses a very small gas amount to the control valve 16, which through the above mentioned adjustment has opened the passage to the upper side of the membrane 27 and which gas pressure temporarily augments the pressing force of the valve plate 14 against the valve seat 15. Breathing gas is then pressed into the patient's respiratory passages.

During the initial phase of the expiration the first portion of the expiration gas will flow into the compressed flexible container 3, which is filled with a mixture of expirated gas and fresh breathing gas, as is shown in fig. 5. Due to the fact that fresh breathing gas continuously is supplied into the supply chamber 6 through the ejector 7 a weak negative pressure is created at the low pressure side 31 of the ejector, which causes an evacuation of the control conduit 23 and the space above the membrane 27 so that the pressure against the valve plate 14 is ceased and at continued expirated used breathing gas can lift the valve plate 14 of the nonreturn valve 9, as is shown in fig. 6.

Instead of manually acuating the flexible container 3 concurrently with the expiration- and inspiration frequency, the container can be contained in a respirator device 32, according to figs. 7-9, which in a known manner pneumatically compresses the container 3 concurrently with the inspiration. The valve means 5 can either be controlled in the same way as is illustrated in the embodiment according to figs. 4-6 or the control signal for blocking the valve plate 14 of the nonreturn valve can be taken from the pressure vessel 33 of the respirator, which surrounds the flexible container 3. The function is principally the same as described in connection with figs. 4-6, i.e. at assisted inspiration the flexible container 3 will be compressed by a compressed-air source not shown and which is controlled by a pneumatic control unit, e.g. according to the Swedish patent 8103695-6. A control conduit 23 is connected to the pressure vessel, which control conduit in the same way as in previously mentioned embodiments during the filling phase of the expiration prevents that the valve plate 14 at the expiration is lifted from its seat 15, as is shown in fig. 8.

When the pressure against the flexible container 3 is ceased and reduced resp. , by e.g. the opening of an outlet valve 34, the pressure on the upper side of the membrane 27 is also reduced and the valve plate 14 can be lifted from its seat 15, when the pressure in the discharge conduit 4 is increased after the filling of the flexible container 3.

In order to adapt the volume of the flexible container 3 to the breathing volume of the patient the volume of the pressure vessel 33 is variable. This is achieved by means of a bottom 37 which is axially displaceable in the pressure vessel.

In the embodiments shown in figs. 1-9 the valve means 5 is shown on an enlarged scale as compared to the patient and also its position on a relatively large distance from the supply chamber 6, has been chosen in order to have an illustration of the function as clear as possible. In practice the valve means 5 will be located in the immediated vicinity of the ejector 7, so that the control conduit 23 will be as short as possible.

Considering sterility requirements it is desired that the parts of the valve means through which the patient's breathing gas flows are detachable from the actual valve unit. Such an embodiment is shown in fig. 11 where the nonreturn valve's 9 passage part 34 through which the expiration gas flows forms a unit which is detachable from the control valve unit 16. This is by means of an appropriate connection means, e.g. a bayonet coupling, connectible to teh underside of the valve means, at which the membrane 27 of the nonreturn valve 9 with the valve plate 14 is fixed to the passage part 35. This can either be designed as a throw-away .article, but can also be reused a plurality of times as it is easy to clean.

Tests performed with the device according to the invention in an advanced lung model, where a very realistic spontaneous as well as controlled ventilation can be simulated, proved that the valve functions in the intended manner. At simulated spontaneous ventilation a BOC-test lung has been connected to the model.

At spontaneous ventilation there is no alveolar rebreathing unless the fresh gas flow is reduced to a level equal to the alveolar ventilation, e.g. there is an optimum fresh gas economy. At controlled ventilation this low fresh gas supply can continue without the occurance of alveolar rebreathing. . .

As a summary it can be stated that with the device according to the invention there is provided an optimum fresh gas economy for Mapleson's system irrespective of how the ventilation takes place.

Claims

λlCLAIMS

1. A device in artificial respiration- and/or anaesthetic systems comprising: a first conduit (2) extending from an inhalation member (1 ) connectible to the patient, said first conduit being arranged for the supply of gas from a gas source; a second conduit (4) for removal of exhalated gas; a flexible container (3) arranged in said first container (1 ) at some distance from the inhalation member (1 ) ; and a stop valve (6) arranged in said second conduit (4) at some distance from the inhalation member (1 ) , said valve (6) being arranged to close by means of a membrane (27) or the like by the action of pressurized gas from the system, c h a r a c t e r i z e d i n , that the stop valve (6) comprises a second manually adjustable control valve (16) , which in a first end position is arranged to provide a flow communication (24,25,26) between the pressure face of the membrane (27) and the pressurized gas, and in a second position is arranged to shut off the supply of gas and open a communication passage (28,29) between the pressure face of the membrane and the atmosphere.

2. A device as claimed in claim 1 , c h a r a c t e r i z e d i n , that the gas conduit (23) of the pressurized gas at the end remote from the control valve (16) is connected to the low pressure side (31 ) of an ejector (7) , through which the respiration gas is arranged to flow continuously.

3. A device as claimed in claim 2, c h a r a c t e r i z e d i n , that the flexible container (3) is arranged in a pressure vessel (33) which forms a part of a respirator device (32) , a control unit being arranged to intermittently control the insufflation pressure in the pressure vessel, said pressure vessel (33) being connected to the control valve ( 16) of the valve means (5) , so that a pressure increase in the pressure vessel can act upon the pressure side of the membrane (27⁾ . λl>

4. A device as claimed in claim 1 , c h a r a c t e r i z e d i n , that the passage portion (35) of the nonreturn valve (9) through which breathing gas flows is detachable from the control valve (16) , at which the membrane (27) of the valve is arranged to liquid-tightly seal the end of said passage portion (35) facing the control valve.