ANAESTHESIA-BREATHING APPARATUS

Abstract: An anaesthesia-breathing apparatus by means of which gas can be supplied to a patient for artificial respiration, supported respiration, anaesthesia purposes or combinations of such purposes, said apparatus comprising a gas chamber (1) connected, on the one hand, to a patient connecting piece (3) and, on the other hand, a respiratory gas receptacle (7), for example in the form of a respiration bag (7), a check valve (15) adapted to permit discharge of excess gas from the breathing apparatus to the atmosphere and, optionally a filter (9) for absorption of carbon dioxide from recirculating breathing gas, is not required in analogy with known apparatuses to be provided in respect to the patient's security during manual operation of the respiration bag with a security valve and a venting valve, provided that in accordance with the invention the gas chamber (1) is in communication with the patient connecting piece (3) via a control valve (4) which alternatively conducts exhaled gas to one end of a recirculation gas chamber (5) or closes the communication to the recirculation gas chamber (5) and conducts the exhaled gas from the gas chamber (1) to the patient, said recirculation gas chamber (5), which at least holds the volume of gas exhaled by a grown-up person that has been in contact with the lung alveoli, at its other end is connected, via a second check valve opening towards the respiratory gas receptacle, to the said respiratory gas receptacle (7), a side duct (11) which is in communication with the atmosphere via said first check valve, being connected to the recirculation gas chamber (5) near said one end, while a connection (12) for supplying fresh gas from a pressurized source opens into the recirculation gas chamber (5) immediately upstream said second check valve (10).

Description: Anaesthesia-breathing apparatus The object of the invention is- an anaesthesia-breathing apparatus by means of which gas can be supplied to a patient for artificial respiration, supported respiration, anaesthesia purposes or combinations of such purposes. Such apparatuses which for example are known from Swedish published specification 7308537-5 or US patents 3.814.091 and 3.901.230 comprise a gas chamber connected, on the one hand, to a patient connecting piece and, on the other hand, a re¬ spiratory gas receptacle, for example in the form of a re- spiration bag, a check valve adapted to permit discharge of excess gas from the breathing apparatus to the atmosphere and, optionally, a filter for absorption of .carbon dioxide from recirculating breathing gas. Most closely related with the object of the invention as far as the function is concerned is the anaesthesia-breathing apparatus according to the above-mentioned US speci ications 3.814.091 and 3.901.230. The apparatus shown fundamentally in Fig. 3 of US specification 3.901.230 operates substantially in the same way as the apparatus according to the present invention in such cases when the patient is breathing spon¬ taneously. Both apparatuses operate in this case according to the well-known Magill-narσosis-breathing system. When the known apparatus is used for performing controlled ventilation or supported ventilation which is a transition form between spontaneous respiration and controlled ventilation, the known apparatus, however, has drawbacks which may involve a danger for the patient. In all the embodiments described in the US patent a closure of the gas discharge valve can take place when the breathing bag is manually operated. If this happens the system is filled with fresh gas causing the pressure to increase. For this reason the provision of a security valve in this system is required in order to prevent the built-up of dangerously high pressures in the lungs of the patient in consequence of the gas supply; in addition the known appara¬ tus requires the provi s ion of a venting valve which upon manual operation permits discharge of gas from the excessive¬ ly filled system to permit the state of locking to be removed. The apparatus construction according to the present invention completely removes these and other drawbacks by a construc¬ tion involving that the gas chamber is in connection with the patient connecting piece via a control valve which alterna¬ tively conducts exhaled gas to one end of a recirculation gas chamber or clos es the connection to the recirculation gas chamber and conducts the exhaled gas from the gas chamber to the patient, said recirculation gas chamber, which at least holds the volume of gas exhaled by a grown-up person that has been in contact with the lung alveoli, at its other end is connected, via a second check valve opening towards the respiratory gas receptacle, to the respiratory gas recep¬ tacle, a side duct, which is in connection with the atmos- phere via said firs t check valve, being connected to the recirculation gas chamber near said one end, while a connec¬ tion for supplying fresh air from a pressurized source opens into the recirculation gas chamber immediately upstream said second check valve . If an apparatus having these characteristic features is used by patients the breathing function of which is paralysed and which thus must be supplied controlled or at least supported ventilation, the control valve and the second check valve cooperate in such a way that during the inhalation phase, when the respiration bag is compressed, an independent recirculation gas chamber is defined in such a way that the inflating pressure cannot enter therein. As the fresh-gas supply and the first check valve, i.e. the discharge valve, both are in connection with the recirculation gas chamber as defined, the following advantageous properties which are not achievable with the apparatuses known so far, are obtained in the present apparatus: 1. No adjustment of the first check valve are required during transition between spontaneous respiration and con¬ trolled ventilation (increased-pressure ventilation) . 2. The supply of fresh gas cannot produce a pressure in the system in excess of the opening pressure of the first check valve, the discharge valve. 3. The opening pressure of the discharge valve, i.e. the first check valve, can be chosen at a very low value. 4. Under no circumstances an undesirable closure of the discharge valve can occur due to the flow conditions in the flow circuit or due to the operation of the respiration bag. 5. The fresh gas can displace the alveolar expiration gas from the system not only during the last part of the exhala¬ tion phase after the respiration bag has become filled, but also during the whole inhalation phase. This means that the apparatus permits a "orderly" displacement of the alveolar expiration gas present in the recirculation gas chamber during an extended period in comparison with the above-men¬ tioned US patent where only the last part of the expiration period is disposable for this purpose. At a given adjustment of the fresh-gas supply the apparatus according to the invention accordingly will displace alveolar gas at a highly increased efficiency which means improved fresh-gas economy. In a particularly advantageous embodiment of the invention the recirculation gas chamber near the control valve has the shape of a convergent-divergent duct, the side duct being connected to the recirculation gas chamber at the most constricted portion of the convergent-divergent duct. The above-mentioned and other embodiments of the obj ect of the inventi on a s w e l l a s the way o f operation o f th e apparatus are explained hereafter by reference to the attached drawings in which Figs. 1-4 schematically and in section show an embodiment of an anaesthes ia-breathing apparatus according to the inven¬ tion, fig. 1 showing the parts of the apparatus in the posi¬ tion corresponding to the inhalation phase, fig. 2 in the position corresponding to the initial portion of the exhala¬ tion phase, fig. 3 in the position corresponding to the sub¬ sequent portion of the exhalation phase and fig. 4 in the position corresponding to the pause between inhalation and exhalation, F igs . 5 and 6 show in re spective ly longi t udi nal and transverse section schematically another embodiment of the anaesthes ia-breathing apparatus according to the invention, and Fig. 7 schematically and in section shows another embodiment of the anaesthes ia-breathing apparatus according to the invention. In the breathing apparatus according to Figs . 1 to 4 the following apparatus parts can be distinguished: A gas chamber 1 occupying the interior of a corrugated flexible hose 2 having stiff walls and rounded cross section is at the upstream end in open communication with a filter 9 for the absorption of carbon dioxide from recirculating breathing gas , said filter in turn at the upstream end being in communication with the breathing bag 7 of normal type. It is to be noted that the fi lter 9 from a functional point of view is not a necessary part of the apparatus and that not either its position as shown here is the only possible one. At the downstream end the gas chamber 1 is in communication with a patient-connecting piece 3 via a control valve 4 which alternatively conducts exhaled gas either to one end of a recirculation gas chamber 5 or closes the communication to the recirculation gas chamber 5 and conducts the respiration gas from the gas chamber 1 to the patient. The control valve 4 comprises a valve housing 4a having three connection ports 4b, 4c and 4d, port 4b leading to the gas chamber, port 4d into the patient connecting piece 3 and port 4c into the recirculation gas chamber 5. A valve device 4e may assume different opening or closing positions in coopera- tion with seats formed about ports 4b and 4c, valve element 4e in the one position during supply of respiration gas to the first port closing the communication from valve housing 4a to the other port 4c and simultaneously permitting the respiration gas supplied to flow via valve housing 4a to the third port 4d intended to communicate via connecting piece 3 with the respiratory ducts of the patient, whereas when the pressure is discharged at the first port 4b valve device 4e is actuated by the pressure existing at the third port 4d due to a pressure increase in the lungs of the patient, so that the first port 4b is closed and the exhaled gas is conducted through valve housing 4a from the third port 4d and out through the second port 4c. In the same way as in gas chamber 1 the greater part of the wall of the recirculation gas chamber 5 consists of a corrugated flexible hose 6 having stiff walls and rounded cross section, said chamber 5 at the upstream end being supplied with exhaled gas from the patient connecting piece 3 through the control valve 4 in the way as described above, whereas the chamber 5 at the other end is in open communica¬ tion with a connection 12 through which fresh gas is supplied OMFI y ΛVyrm Wii'" ° from a pressurized source . Close to control valve 4 the recirculation gas chamber 5 has the shape o f a convergent-divergent duct in the mo s t restricted portion 13 of which a side duct 11 is connected which at the oppos ite end is in communication with the atmosphere via an outwardly opening check valve 15 . At the end where the fresh-gas supply connection 12 opens into the recirculation gas chamber 5 this chamber 5 connected to the respiratory gas receptacle 7 or to the connection thereof with gas chamber 1. A check valve 10 opening towards the respiration gas receptacle, i. e. the respiration bag 7 , is provided in the recirculation gas chamber 5 immediately downstream connection 12 for supplying fresh gas . The way of operation of the apparatus described above is as follows : Du ring the in f lation phas e i l lustrat ed in Fi g. 1 the respiration bag 7 is compressed causing the check valve 10 to close the communication between the respiration bag and the recirculation gas chamber 5 so that gas from bag 7 flows through filter 9 and chamber 1 to the patient connecting piece 3 through the control valve hous ing 4a in which conditions are such that the communication with the recir¬ culation gas chamber 5 is closed by valve device 4e. During the expiration phase, i. e. during the patient's exhalation, exhalation air will initially flow from the patient connecting piece 3 through the valve housing ports 4d and 4c into the recirculation gas chamber 5 while valve device 4e closes the communication with gas chamber 1. The exhalation gas which initially to the greater part comprises unused gas , i. e. gas which has not been in contact with the lung alveol i of the patient, enters into the recirculation gas chamber 5 and flows together with newly supplied gas from connection 12 past check valve 10 into the respiration bag 7 which is in a state of expansion. During the latter part of the expiration phase, after filling of the respiration bag 7 and balancing of the pressure in this bag in relation to the expiration pressure, the subsequently exhaled portion of the exhalation gas which predominantly comprises gas that has been in contact with the lung alveoli, will be discharged through side duct 11 and check valve 15 to the extent this gas is prevented from entering the recirculation gas chamber 5 due to the presence therein of previously received exhala¬ tion gas together with fresh gas supplied from connection 12. This latter part of the exhalation phase is illustrated in Fig. 3. Finally, Fig. 4 shows the pause between the patient's exhalation and the subsequent inhalation phase initiated by renewed compression of the respiration bag 7. During this pause exhalation air previously received in the recirculation gas chamber 5 will be displaced by fresh gas supplied from connection 12. The gas supply is so adjusted that the gas leaving the side duct 11 through check valve 15 entirely or predominantly comprises used exhalation gas. From Fig. 1 it appears that during the inhalation phase the expulsion of previously exhaled gas from the recirculation gas chamber 5 by fresh gas entering from connection 12 will continue, the inflow through connection 12 obviously being dimensioned in respect to the whole length of time during which there will be no outflow of gas from the recirculation gas chamber 5 to the respiration bag 7, i.e. the latter part of the exhalation phase (Fig. 3), the pause (Fig. 4) and the inhalation phase (Fig. 1). In the construction according to Figs. 5 and 6 a considerable constructive simpli ication is obtained by exploiting the fact that three parallell flow ducts, the gas chamber 1, the recirculation gas chamber 5 and the side duct 11 may be combined in such a way that one of the ducts, in the case of Figs. 5 and 6 the side duct 11, is bounded by a thin-walled flexible casing enclosing the two other ducts, in the example shown gas chamber 1 and recirculation gas chamber 5, these two latter chambers consisting of hoses 2 and 6 respectively that may be corrugated and which have stiff, but flexible walls. These adjacent hoses 2 and 6 deform the casing 14 to an oval cross sectional shape, the cavities formed between the outer surfaces of the hoses and the casing constituting side duct 11 which connects recirculation gas chamber 5 via the first check valve 15 with the atmosphere. In analogy to the embodiment according to Figs. 5 and 6 it is possible that gas chamber 1 and side duct 11 are hoses of rounded cross section having stiff but flexible walls, for example corrugated hoses, which are enclosed in a flexible casing 14 with a thin wall, said casing being deformed by the two enclosed hoses into an oval cross section shape and connected in such a way with at least one of the enclosed ducts that the cavity formed between the outer surfaces of the hoses and the casing forms the recirculation gas chamber 5. in the construction according to Fig. 7 the control valve 4 is connected with the patient connection piece 3 via a T- branch 18 and two extension hoses 16 and 17 enabling the comparatively big control valve 4 to be mounted stationarily spaced from the patient. In the embodiment according to Fig. 7 the control valve 4 comprises a housing 4a having four communication ports 4b, 4c, 4f and 4g, out of which port 4b communicates with gas chamber 1, port 4c communicates with recirculation gas chamber 5 and ports 4f and 4g are respec¬ tively inlet and outlet connections with the patient connec- tion piece 3 via extension hoses 16 and 17 respectively. The valve devices in the control valve 4 comprise a directional OMPI i WΪPO valve (check valve) 4h and a bellows valve 4i which upon the supply of respiration gas to the first port 4b permit flow through port 4f while simultaneous ly the bellows valve 4i closes communication from port 4g to port 4c. This condition i s illustrated in Fig. 7. When the pres sure in gas chamber 1 (and thereby in port 4b) i s releas ed the exhalation air (expiration gas ) will be permitted to flow from port 4g out¬ wardly through port 4c, while directional valve 4h closes the communication in a backward direction from extension hose 16 via port 4f. As for the rest, the embodiment according to Fig. 7 wil l operate in the same way as the two previous ly described embodiments .

Claims: WHAT WE CLAIM IS: 1. Anaesthesia-breathing apparatus comprising a gas chamber (1) connected, on the one hand, to a patient connecting piece (3) and, on the other hand, a respiratory gas receptacle (7), for example in the form of a respiration bag (7), a check valve adapted to permit discharge of excess gas from the breathing apparatus to the atmosphere and, optionally, a filter (9) for absorption of carbon dioxide from recircula¬ ting breathing gas, c h a r a c t e r i z e d in that the gas chamber (1) is in communication with the patient connecting piece (3) via a control valve (4) which alternatively conducts exhaled gas to one end of a recirculation gas chamber (5) or closes the communication to the recirculation gas chamber (5) and conducts the exhaled gas from the gas chamber (1) to the patient, said recirculation gas chamber (5), which at least holds the volume of gas exhaled by a grown-up person that has been in contact with the lung alveoli, at its other end is connected, via a second check valve opening towards the respiratory gas receptacle, to the said respiratory gas receptacle (7), a side duct (11) which is in communication with the atmosphere via said first check valve, being connected to the recirculation gas chamber (5) near said one end, while a connection (12) for supplying fresh gas from a pressurized source opens into the recirculation gas chamber (5) immediately upstream said second check valve (10). 2. Anaesthesia-breathing apparatus as claimed in claim 1, c h a r a c t e r i z e d in that the recirculation gas chamber (5) in the neighbourhood of the control valve (4) has the shape of a convergent-divergent duct and that the side duct (11) starts from the recirculation gas chamber (5) at the most restricted position (13) in the convergent-divergent duct. 3. Anaesthesia-breathing apparatus as claimed in claim 1, c h a r a c t e r i z e d in that the control valve comprises a valve housing having three communication ports as well as a valve device which during supply of respiration gas to the first port closes the communication from the valve housing to the second port and at the same time permits the respiration gas supplied to flow via the valve housing to the third port, arranged to be connected with the respiratory ducts of the patient, and which upon release of the pressure at the first port is actuated by the pressure prevailing at the third port due to the pressure increase in the lungs of the patient so as to be reversed causing the first port to be closed and the exhalation gas to be conducted through the valve housing from the third port and out through the second port. 4. Anaesthesia-breathing apparatus as claimed in claim 1, c h a r a c t e r i z e d in that the gas chamber (1) and the recirculation gas chamber (5) are flexible hoses with stiff walls and rounded cross section, e.g. corrugated hoses, which are enclosed within a flexible casing (14) having a thin wall, this casing being deformed by the two enclosed hoses into an oval cross sectional shape and is so connected with at least one of the enclosed ducts that the cavity formed between the outer surfaces of the hoses and the casing forms the side duct (11) connecting the recirculation gas chamber (5) with the atmosphere via the first check valve (15). 5. Anaesthesia-breathing apparatus as claimed in claim 1, c h a r a c t e r i z e d in that the gas chamber (1) and the side duct (11) are flexible hoses with stiff walls and rounded cross section, e.g. corrugated hoses, which are enclosed within a flexible casing (14) having a thin wall, this casing being deformed by the two enclosed hoses into an oval cross sectional shape and is so connected with at least one of the enclosed ducts that the cavity formed between the outer surfaces of the hoses and the casing forms the recirculation gas chamber (5). 6. Anaesthesia-breathing apparatus as claimed in claim 1, c h a r a c t e r i z e d in that the control valve (4 in Fig. 7) comprises a valve housing (4a) having four communication ports (4b, 4c, 4f, 4g) as well as a valve device (4h, 4i) which upon supply of respiration gas to the first port (4b) closes the communication from the valve housing (4a) to the second port (4c) and at the same time permits the respiration gas supplied to flow via the valve housing (4a) to the third port (4f ) intended to be connected to the respiratory ducts of the patient, and which upon release of the pressure at the first port (4b) is actuated by the pressure prevailing at the third port (4f) due to an increase of pressure in the lungs of the patient so as to be reversed, causing the first port (4b) to be closed and the exhalation gas to be conducted through the valve housing (4a) from the third port and out through the second port (4c) . 7. Anaesthesia-breathing apparatus as claimed in claim 6, c h a r a c t e r i z e d in that the control valve (4) is connected with the patient connecting piece (3) by means of a T-branch (18) and two extension hoses (16, 17) enabling the comparatively large control valve (4) to be stationarily mounted spaced from the patient. 8. Anaesthesia-breathing apparatus as claimed in claim 6, c h a r a c t e r i z e d in that the valve device (4h, 4i) comprises, on the one hand, a directional valve (4h) controlling the third port (4f), and, on the other hand, a bellows valve (4i) closing or opening the communication between the fourth communication port (4g) and the second communication port (4c) depending on the pressure prevailing in the first port (4b) and in the connecting hose (17) leading away from the patient connecting piece (3). 0_V.PI

Inventors: KOHNKE O, RUEBEN H
Applicants: KOHNKE O, RUEBEN H, TESTA LAB A S, TESTA LAB AS
Application year: 1981
Main classification: A61M17
IPC codes: A61M16