US2428451A - Pressure resuscitator - Google Patents

Description

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"I V W'- Oct. 7, 1947. EMERSQN 6 2,428,451

PRESSURE RESUSCITATOR Filed Feb. 17, 1945 Sheets-Sheet l y 4 I 4 f? I f? 2.0 9

Oct. 7, 1947.

J. H. EMERSON PRESSURE RESUSCITATOR.

2 Sheets-Sheet 2 Filed Feb. 17, 1945 Patente d Oct. 7, 1 947 UNITED STATES"PATENT OFFICE 8 Claims. (Cl. 128-29) This invention pertains to resuscitators, andrelates more especially to a pressure resuscitator of the kind in which air or oxygen is intermittently forced into the lungs of the patient so as "to infiate the lungs, the deflation of the lung depend ing upon the elasticity of the latter. This kind of resuscitator is much simpler and less expensivethan that type wherein the lung is positively deflated by aspiration. While'the asp-irator type of resuscitator is doubtless to bev preferred when available, the simpler pressure type is far superior, in results attained, to mere manipu1a;-' tive methods of resuscitation and by reasoniiof' its relative cheapness, simplicity and small'size', may be made more generally available than the aspirator type. l V f 1 While the pressure type of resuscitator as heretofore constructed has many desirablecharacteristicsit is subject in operation to one defect which in the hands of the unskilled user. may lead to serious consequences. The pressure type of resuscitator is usually supplied with "air or gas by means of a pump of reciprocating type (for example a bellows or a piston working in a cylinder). During the pressure stroke, the air or gas is delivered to the lungs. Usually appropriate valve means is provided whichautomath cally closes an outlet leading from the lungs to the atmosphere during the pressure stroke and which automaticall open during the suction stroke. This arrangement in theory is wholly satisfactory, and operates as intended so long as the user continues properly to actuate the pump, but if the operator stop, particularly during or at the end of the pressure stroke, the outlet valve remains closed and if the operation is not at once resumed the patient may suffocate.

A principal object of the present invention is to provide a pressure type resuscitator having provision for automatically relieving the lung pressure whenever the reciprocating pump element is stopped during or at the end of its pressure stroke. safety release device of improved type which may be embodied in pressure resuscitators of various kinds, for example, those in which the pressure fluid is delivered to the face mask by a manually actuable bellows device rigidly connected to the mask, or in which the pressure fluid is delivered to the face mask by means of a flexible conduit from a pump or other source of intermittent pressure even though such source be remotely located. A further object is to provide a resuscitator device of simple, inexpensive type, easily operated A further object is to provide a even by an unskilled person, and of small weight and dimensions so that it is readily portable. Other and further objects and advantages of the invention will be pointed out in the following more detailed description and by reference to the accompanying drawings, wherein Fig, 1 is a side elevation illustrating a pressure resuscitator of the kind in which the pump is of bellows type, this resuscitator embodying the present invention;

Fig. 2 is a fragmentary section to larger scale, substantially on the line 22 of Fig. 1;

Fig. 3 is a fragmentary section to larger scale on the line 3-3 of Fig. 1; a

Fig. 4 is a section substantially on theline 44'of Fig. 2;

Fig. 5 is aside elevation to small scale, illustrating a modification, particularly an embodiment designed for use with a remotely located pump or other source of pulsating pressure;

Fig. 6 is a vertical section through the device of Fig. 5, showing details of construction;

Fig. 7 is a fragmentary vertical section illustrating a further embodiment ofv theinvention, and showing a reciprocating pump as the device for providing the pulsating pressure, the pump piston being shown at the beginning of its pressure stroke;

Fig. 8 is a view similar to Fig. 7, but showing the pump piston nearing the end of its pressure stroke, and indicating the position of the inlet and outlet valves of the resuscitator at this time;

Fig. 9 is a View similar to Fig. 8, but showing the position which the parts occupy just after the pump piston begins the upstroke;

Fig. 10 is a view similar to Fig. 8, but indicating the position which the parts occupy when the pump piston is at the lowermost portion of its pressure stroke and just before it starts its upward stroke; and

Fig. 11 is a. view similar to Fig. 10 'but showing the position which the parts assume if the pump piston is left standing at the lower end of its pressure stroke.

Referring to the drawings, and in particular to Figs. 1 to 4 inclusive, the face mask of the resuscitator device is indicated at M. This face mask may 'be of conventional type, here shown as comprising the inflatable face-engaging portion I and the rigid tubular stem 2 provided with the bore 3 (Fig. 3) through which the gaseous medium passes to and from the mask.

As'illustr'ated in Fig. 3, this stem 2 is integral with the valve case 4, the stem and the valve case beingmade of any suitable material, for ex- 3 ample metal or a moulded plastic. While as here illustrated the stem 2 and the case 4 are integrally joined, it is obviously within the invention to make them as separate parts and unite them in any appropriate Way.

The case 4, as illustrated in Figs. 1 and 3, con-- stitutes the normally fixed head of a pump of bellows type comprising the expansible-contractible bellows 5 of any suitable material, for instance leather, rubber, or treated textile fabric, and which is closed at its opposite end by the movable head 6 (Fig. 2). The head 6 comprises, the annular cylindrical portion 1, and the bellows member 5 is provided with an elastic sleeve pore tion 8 which is expanded and slipped over the part I so as to provide a leak-tight union between the bellows member 5 and the head 5. In the same way the opposite head 4 is provided'with the annular cylindrical member 9 over which the opposite sleeve portion iii of the bellows device is drawn, the material of the bellows beingsufilciently elastic to vprovide a leak-tight union with the opposite heads. However, if the case 4 be made of'two separable parts clamped together, as illustrated in Fi 6, the marginal portion of the bellows may be clamped, together with the margin of the diaphragm, between these casing parts.

The head 6 is preferably provided with a, cover plate ll attached to the head 5 by the bolts 42, the cover I i being provided with a handle it, here shown as aloop into which the operators hand may be slipped, the cover 5! also having one or more air inlet ports of: largecapacity.

The head 5 is furnished with a suction port 5 (Fig. 2) leading to the interior of the bellows 5. This port is controlled by an' inwardly or downw'ardly opening valve it. The head 6 is also furnished with one or more relief ports each nor: mally closed by an outwardly or upwardly opening valve ll. Two such valves are here shown (Fig. 4), both valves being'urged toward port closing position by means of a spring l8. This spring is is of such strength as to keep the valve I! closed until a predetermined pressure has been built up in the patients lungs, whereby these valves open automatically to avoid the application of undue pressure to the lungs. Preferably, a leak port 3.5 of small capacity is provided in the'head 5' (Fig. 2). However, if the valves do not seat leak-tight, the leakage through the closed valves will accomplish the same result as the leak port, and the latter is not always necessary.

The casing member 4 (Fig. 3) is provided with an annular internally directed flange it which forms a support for the outer margin of an annular diaphragm .28, the margin of the diaphragm being clamped leak-tight to the flange 9 by a clamping ring 19 This diaphragm, s illustrated in Fig. 3, constitutes the upper wall of avalve chamber C within which is arranged the annular valve seat 2!, here shown as integral with the member 4 and coaxial with the mask stem 2. The space 22 within this valve seat 2| communicates freely with the bore 3 in the mask stem; An annular outletvalve 23 is arranged to cooperate with the seat 2 i, this outlet valve 23 i being secured to the inner margin of the diaphragm 25) in coaxial relation with the latter;

An' inletvalve disk 24 is arranged to engage the under surface of the outlet'valve 23 and thereby to closethe'inletportifi at the center of the valve 23. This'inlet valve 24 is uided and restrained in its movements by a cage 26 extending downwardly from the lower side of the annular valve 23, and within this cage there is'arranged a relatively light spring 27, which tends to keep the inlet valve 24 in closed position. A relatively heavy spring 23 reacts against the cage 26 and tends to move the diaphragm upwardlyso as to separate the outlet valve 23 from the seat 2|.

The part 4 is provided with one or more ports 7 29 leading from the chamber C, surrounding the ve s a 2|, to the uter a mos he While the springsll and28; as here illustrated, are compression springs, it is contemplated that tension springs may be employed.

- A modified construction is illustrated in Figs. 5

and-'6 designed for use with a pump or other source of intermittent pressureremote from the a face mask. In this arrangement there i provided a casing member 3! here shown as integral with" the tubular stem 32 to which the face mask may be secured in any desired manner. The part 3| is provided with an annular upstanding wall 33, with which cooperates the downwardly directed annular wall 34 ofthe upper member 35 of the valve case, the parts 33 and 34 clamping the outer margin of an annular diaphragm 36. be 7 tween them. The parts 3| and 35 are united by suitable bolts 3'! (Fig.5) to form a leak-tightcasing. 7/

The annular outlet valve 38 is secured by means of a clamping plate 39 to the inner margin of the diaphragm 36. This annular valve 38 cooperates with'an annular valve seat 38% here shown as integral with the part 3| and coaxial with the member 32. I The aperture 40 at the center of the. valve 38 constitutes an inlet port leading 'from' the upper part of thecasing to the bore in the part 32. A valve-guiding cage 4| extends downwardly from the valve 38 and is engaged by a relatively heavy spring 42 whose lower end abuts a shoulder 43 at the interior of the part 32, this spring urging the valve 38 away from the seat 38*. Within the guiding cage 4| there' is arranged an inlet valve disk 44 which cooperates with the inner margin of the valve 38 to close the passage 40,, a relatively light spring'45 reacting between the cage 4| and the valve disk and tending tokeepthe valve disk 44 in closed position.

To the part 35 of the valve case there is secured leak-tight an elbow 46 having the nipple portion 41 designed to receive the end of a flexible hose leading from a suitable pump or other source of intermittently applied pressure. The lower member 3| of the valve case i provided with one or more ports 41 of large capacity leadingfrom the space-48, beneath the diaphragm 36 and 'sur trated (Fig. 9) as integrally joined to the lower member 5| of the valve casing; The peripheralwall of this valve casing is furnished withan inwardly directed flange 52 forming a support for the outer margin of the flexible diaphragm 53. The lower member of the casing is also furnished. With an annular valve seat 54 coaxial with the stem member 50' and with which cooperates the annular outlet valve 55 which is secured to the inner margin of the diaphragm 53 in coaxial re.- lation with the seat 54. A relatively heavy spring 56 engages the valve 55 and urges the latter away from the seat 54; The valve 55 has the central port 51 (Fig. 9) providing for passage of fluid from the plenum chamber P above the diaphragm to the space inside the valve seat 54, and. an inlet valve disk 58 is arranged so that it tends to close this port 5l,-the valve being urged toward portclosing position by a relatively light spring 59 which is anchored to a part 60 secured to the outlet valve 55. The term plenum chamber as thus applied to the space within the apparatus and above the diaphragm, is used merely for con- Venience in distinguishing among the various spaces and cavities and is intended to designatethat space in which during inhalation (but not necessarily during exhalation) a superatmospheric-pressuresubsists and from which during inhalation gaseous medium passes through the inlet valve to the facemask' and lungs. Y

The valve casing also comprises the upper member 6| which is connected to the part 5| in any appropriate way, for example by bolts (not shown), the margin of the diaphragm 53 being'clamped leak-tight between the opposed portions of the casing members 5! and BI. The upper 'member SI of the case is furnished With a tubular stem or nipple (54, and is provided with aleak port 65 of small capacity. The lower membar 5! of the case is also furnished with one or more ports 66 of large capacity leading from the space beneath the diaphragm and surrounding the valve seat'54 to the'outer atmosphere. As hereill'ustrated, the pressure fluid is supplied to the valve casing by means of a pump comprising the cylinder 5! and the reciprocating piston 68, the cylinder being provided with a delivery nipple 59 which may-be'integral with the member 64 "of the valve casing or which may be connected to'the latter in any desired manner, and at any appropriate distance from the valve casing. As illustrated. the piston 58 is provided with a port 50' which is controlled by a valve 1| cooperable with an annular seat l2 (Fig. 9) the valve H being urged toward the seat by a spring 13 anchored to a support M carried by the piston. The piston is reciprocated by means of a piston rod 15 (Fig. 8) which may be actuated by hand or by power, as desired. The operation of the device as illustrated in Figs. '7 to- 11 is substantially as follows:

As shown in Fig. '7 a piston 68 has completed its up-stroke and has started down with its valve 'H seated. When the piston starts down the gaseous medium within the cylinder is compressed, the diaphragm is fonced down so as to seat valve 55, and as the pressure further increases the inlet valve 58 is moved away from its seat; the gaseous medium from plenum chamber P now passes down through the open inlet port 5'! and into the tubular member 50, as indicated by the arrows (Fig. 8) and then into the face mask. Some of the gaseous medium also escapes to the'at-mos-phere through the leak port 55/ If, as is intended, the pump piston 68 begins its'return or suction stroke withoutpause, the parts assume the relative positions shown-in Fig. 9, the valve H in the piston opening to admit air to the space within the pump cylinder beneath the piston, the inlet valve 58 closing, and the diaphragm 53 rising in response both to the suction and to the action of the spring 55, thereby providing free communication between the interior of the tubular stem 50 and the space heneath the diaphragm and outside of the valve seat 54. The natural elasticity of the lung now causes the lung to contract, forcing out the air from the lung through the face mask, through still subsisting in chamber P, the parts wouldtinues until the piston 68 reaches the upper end' of its path of travel, thus completing the cycle. If, instead of starting back on its suction stroke immediately after completing or partially completing its pressure stroke, the piston should become stationary with superatmospheric pressure for the instant occupy the positions shown in Fig. 10, all of the several valves being closed. With the parts in this position the gaseous medium is under some degree of pressure within the plenum chamber P above the diaphragm, but the lung cavity is completely out off from the out-' side atmosphere and there is no way for the 'air from the lung to escape. vision of the leak port 68, the pressure in' the plenum chamber above the diaphragm (said chamber being of small capacity) begins immediately to drop, since the piston 68 is now stationary. As soon as the pressure in the chamber P has dropped even to a very slight degree, the diaphragm 53 is unable longer to resist the upward urge of the spring 56 and thus the latter raises the outlet valve 55 from the seat 5'4, as shown in Fig. 11, providing free communication between the lung cavity and the outer atmosphere. Thus, with this arrangement, there is no possibility that the patient may be suffocated by failure of the operator to actuate the pump piston in the proper way.

The operation of the devices shown in Figs. 1 to 6 will be obvious, it is believed, from the above description with respect to Figs. '7 to 11'. Thus in the arrangement shown in Figs. 1 to 4 inclusive, the pressure stroke of the upper head 6 of the bellows device first forces the diaphragm down so as to seat valve 23, the valve 24. also being seated. As the pressure in chamber P further increases the valve 24 is unseated. Air from the plenum chamber P (constituted by the interior of the bellows) thus enters the lung through the face mask. On the reverse or suction stroke of the bellows, the valve 24 is closed and the spring 28 raises the valv 23 from its seat. This is the normal operation of the device. If the operator should hold the bellows collapsed, the air from the plenum chamber P, that is to say, the interior of the bellows, gradually leaks out through the leak port 36 in the upper head 6 of the bellows, and, when the pressure has been reduced very slightly, the spring 28 raises the valve 23 from its seat 2!, thus providing free communication between th face mask and the chamber C and the outer atmosphere.

The device shown in Fig. 6 operates in substantially the same manner, it being assumed that pressure is built'up intermittently in the plenum chamber P within the member 46. As the pressure builds up the diaphragm is depressed, seating valve 38. As the pressure further increases the valve 44 is unseated and the gaseous medium from the chamber P passes through the orifice 40 and through the tubular member 32 to the face mask. When the pressure pulsation ceases and a suction impulse begins, the diaphragm 36 rises and unseats the valv 38. If no suction impulse occurs, following a given pressure impulse, the pressure medium contained within the chamber P quickly leaks through the leak port 49 thus reducing the pressure in the chamber P and permitting the from the seat 38 However, by the pro-.-

assent 'W'hlle certain desirable embodiments of the invention have been illustrated and described by way of example, it is tobe understood that the invention is'broadly inclusive of any and all modifications and equivalent constructions falling Within the scope of the appended claims.

I claim:

1. In a resuscitator of the type having a face mask, a plenum chamber wherein a gaseous medium under pressure is periodically supplied, means providing communication between the interior of the plenum' chamber and the interior of the mask and first valve means adapted to open said communication when the pressure in the plenum chamber attains a predetermined amount and to close said communication when it falls below a predetermined amount, the improvement comprising a valve chamber, means providing free communication between the atmosphere and the interior of the face mask through said valve chamber, a diaphragm moveable in response to variations in pneumatic pressure and forming a wall between the plenum chamber and the valve chamber, said diaphragm being constructed and arranged to move inwardly of the valve chamber when the pressure in the plenum chamber attains a predetermined amount and to move outwardly of the valve chamber when the pressure in the plenum chamber falls below a predetermined amount, a second valve means mounted on said diaphragm and adapted to close said communication between the atmosphere and the interior of the face mask when the diaphragm is moved inwardly of the valve chamber and to open said communication when the diaphragm is'moved outwardly of the valve chamber and means providing a relatively slow leakage from the plenum chamber to the atmosphere, whereby upon discontinuing the supply of gaseous medium under pressure to the interior of the plenum chamber for a predetermined interval the pressure in the plenum chamber is automatically reduced by said slow leakage, the pressure-responsive diaphragm automatically moves outwardly of the valve chamber in response to said reduced pressure and said second valve opens said free communication between theatmosphere-and the interior of the face-mask through the valve chamber.

2, a resuscitator of the type having a face mask, a plenum chamber wherein a gaseous medium under pressure is periodically supplied, means providing communication between the interior of the plenum chamber and the interior of the mask and first valve means adapted to opensaid communication when the pressure in the plenum chamber attains a predetermined amount and to close said communication when it falls below a predetermined amount, the improvement comprising a valve chamber, means providing free communication between the atmosphere and the interior of the face mask through said valve chamber, a diaphragm moveable in response to variations in pneumatic pressure and forming a wall between the plenum chamber and the valve chamber, said diaphragm being constructed and arranged to move inwardly of the valve chamher when the pressure in the plenum chamber attains a predetermined amount and to move outwardly of the valve chamber when the pressure in the plenum chamber falls below a predetermined amount, a mechanical guard means constructed and arranged to maintain at all times a free space to accommodate outward movement of said diaphragm, a second valve 8 I means mounted on said diaphragm and adapted to close said communicationbetween the at, mosphere and theinterior of the face mask when the diaphragm is moved inwardly of the valve chamber and to open said communication when. the diaphragm is moved outwardlyof the valve chamber and means providing a relatively-slow leakage from the plenum chamber to the at mosphere, whereby upon discontinuing'the sup, ply of gaseous medium under pressure to the interior of the plenum chamber for a predetere mined interval the pressure in the plenum chamher is automatically reduced by said slow leakage, the pressure-responsive diaphragm automatically moves outwardly of th valve chamber in response to said reduced pressure and said second valve opens said-free communication bee tween the atmosphere and the interior of the face mask through the valve'chamber. v

3. In a resuscitator of the type having a face mask and a plenum chamber wherein a gaseous medium under pressure is periodically supplied; the improvement comprising a valve chamber, means providing free communication between the atmosphere and the interior of the valve chamber, means providing free communication between the interior of the face mask and said valve chamber, a diaphragm moveable in response to variations in pneumatic pressure and forming a wall between the plenum chamber and the valve chamber, said diaphragm being constructed and arranged to move inwardly of the valve ch'amber when the pressure in the plenum chamber attains a predetermined amount and to move cute wardly of the valve chamber when the pressure in the plenum chamber falls below a predeter-imined amount, a mechanical guard means constructed and arranged to maintain a free space to accommodate outward movement of said dla-. phragm, a first valve means mounted on said diaphragm and adapted to close said free communication between the atmosphere and the interior of the valve chamber when the diaphragm is moved inwardly of the valve chamber and to open said communication when the diaphragm is moved outwardly of the valve chamber, a, port in said diaphragm providing communication be tween the plenum chamber and said valve chamber, a second valve means adapted to close said port, a relatively light'spring urging the second valve means toward closed position and-aleak port in said plenum chamber providing a rela-v tively slow leakage from the plenum chamberv to the atmosphere, whereby upon discontinuing the supply of gaseous medium under pressure to the interior of the plenumchamber for a predetermined interval the pressure in the plenum chamber is automatically reduced by said slow leakage, the pressure-responsive diaphragm auto-V matically moves outwardly of the valve chamber in response to said reduced pressure and said first valve means opens said free communication between the atmosphere and the interior of the valve chamber. g

' 4. 'In a resuscitator of the type having a face mask, a plenum chamber wherein a gaseous medium under pressure is periodically supplied by a, pump having a reciprocating part, means pro-. viding communication between the interior of the plenum chamber and the interior of the mask; and first valve means adapted to open said communication when the pressure in the plenum chamber attains a' predetermined amount and to close said communication when it falls below a predetermined amount, the improvement corn;

prising a valve chamber, means providing free communication between the atmosphere and the interior of the face mask through said valve chamber, a diaphragm moveable in response to variations in pneumatic pressure and forming a wall between the plenum chamber and the valve chamber, said diaphragm being constructed and arranged to move inwardly of the valve chamber when the pressure in the plenum chamber attains a predetermined amount and to move outwardly of the valve chamber when the pressure in the plenum chamber falls below a predetermined amount, a mechanical guard means constructed and arranged to maintain a free space for outward movement of said diaphragm; a second valve means mounted on said diaphragm and adapted to close said communication between the atmosphere and the interior of the face mask when the diaphragm is moved inwardly of the valve chamber and to open said communication when the diaphragm is moved outwardly of the valve chamber and means providing a relatively slow leakage from the plenum chamber to the atmosphere, whereby upon discontinuing the supply of gaseous medium under pressure to the interior of the plenum chamber for a predetermined interval, the pressure in the plenum chamher is automatically reduced, the pressure-responsive diaphragm automatically moves outwardly of the valve chamber in response to said reduced pressure and said second valve means opens said free communication between the atmosphere and the interior of the face mask through the valve chamber.

5. In a resuscitator of the type having a face mask, a, plenum chamber wherein a gaseous medium under pressure is periodically supplied by contraction and expansion of the plenum chamber, means providing communication between the interior of the plenum chamber and the interior of the mask and first valve means adapted to open said communication when the pressure in the plenum chamber attains a predetermined amount and to close said communication when it falls below a predetermined amount, the improvement comprising a valve chamber, means providing free communication between the atmosphere and the interior of theface mask through said valve chamber, a diaphragm moveable in response to variations in pneumatic pressure and forming a wall between the plenum chamber and the valve chamber, said diaphragm being constructed and arranged to move inwardly of the valve chamber when the pressure in the plenum chamber attains a predetermined amount and to move outwardly of the valve chamber when the pressure in the plenum chamber falls below a predetermined amount, a mechanical guard means constructed and arranged to maintain at all times a free space to accommodate outward movement of said diaphragm, a second valve means mounted on said diaphragm and adapted to close said communication between the atmosphere and the interior of the face mask when the diaphragm is moved inwardly of the valve chamber and to open said communication when the diaphragm is moved outwardly of the valve chamber and means providing a relatively slow leakage from the plenum chamber to the atmosphere, whereby upon discontinuing the supply of gaseous medium under pressure to the interior of the plenum chamber for a predetermined interval the pressure in the plenum chamber is automatically reduced by said slow leakage, the pressure-responsive diaphragm automatically moves outwardly of the valve chamber in response to said reduced pressure and said second valve means opens said free communication between the atmosphere and the interior of the face mask through the valve chamber. 6. In a resuscitator of the type having a face mask, a plenum chamber wherein a gaseous medium under pressure is periodically supplied, means providing communication between the interior of the plenum chamber and the interior of the mask and first valve means adapted to'open said communication when the pressure in the plenum chamber attains a predetermined amount and to close said communication when it falls below a predetermined amount, the improvement comprising a valve chamber, means providing free communication between the atmosphere and the interior of the face mask through said valve chamber, a diaphragm moveable in response to variations in pneumatic pressure and, forming a wall between the plenum chamber and the valve chamber and a second valve means mounted on said diaphragm and adapted to close said communication between the atmosphere and the interior of the face mask when the diaphragm is moved inwardly of the valve chamber and to open said communication when the diaphragm is moved outwardly of the valve chamber, whereby the pressure-responsive diaphragm automatically moves outwardly of the valve chamber in response to reduced pressure in the plenum chamber causing said second valve to open said free communication between the atmosphere and the interior of the face mask during the exhalation phase of resuscitation and the pressure-responsive diaphragm automatically moves inwardly of the valve chamber causing said second valve means to close said free communication during the exhalation phase of .resuscitation.

7. In a resuscitator of the type having a face mask, a plenum chamber whereina gaseous medium under pressure is periodically supplied, means providing communication between the interior of the plenum chamber and the interior of the mask and first valve means adapted to open said communication when the pressure in the plenum chamber attains a predetermined amount and to close said communication when it falls below a predetermined amount, the improvement comprising a valve chamber, means providing free communication between the atmosphere and the interior of the face mask through said valve chamber, a diaphragm moveable in response to variations in pneumatic pressure and forming a wall between the plenum chamber and the valve chamber, a mechanical guard means constructed and arranged to maintain at all times a free space to accommodate outward movement of said diaphragm and a second valve means mounted on said diaphragm and adapted to close said communication between the atmosphere 7 and the interior of the face mask when the diaphragm is moved inwardly of the valve chamber and to open said communication when the diaphragm is moved outwardly of the valve chamber, whereby the pressure-responsive diaphragm automatically moves outwardly of the valve chamber in response to reduced pressure in the plenum chamber causing said second valve to open said free communication between the atmosphere and the interior of the face mask during the exhalation phase of resuscitation and the pressure-responsive diaphragm automatically moves inwardly of the valve chamber causing said second a aleas 1- the exhalation ishase of i'usc amen 11 a a i-e$uscitatof of the type ha' a face ina-sli and a plenm charms? Wherifi'l 'aeas medium under pressure is periodically -s-1ii5i3'lid; the improvement comprising a Valve chamber, i i'earis' providing free communication betweer'i the-atiiicspheie and the interior of the valve chamber; means providing free communication between the interior of the face mask arid said valve chamber, a, diaphragm moveable in re iid s'e to variations in pneumatic pressure and farming a wall between the plehum chamber and the valve chamber, a mechanical guard means c'o'fistiucted and arranged to maintain a free space to accommodate outward movement of said q-iaphragm,a first valve means'mounted on said diaphragm and adapted to close said. free communioatier i between the atmosphere and the intei'ioi' of the valve chamber when the diaphragm.

is moved inwardly of the valve chamber and to open Said oommuriicatioawhen'the diaphragm i's' moirefi outwardly of the valve chamber, a port iii-Said. diaphragm providing communication between the plenum chamber and said valve cham:

be' a second valve means'adapted to close vsa icl 1561 anaa relatively light spring urging the sec iil valve means toward closed position, whereaii movee o'ufiviiafdly; of the v 'iepeiie' to 'fe'd uc'ed V pressureiii the plenum chambefeausi ag' setidfii'st valve "means tq open saia cation b tween the atmosphere aria nterior at trieface mask auririg ma es: halationhase of resuscitation: anclthe pressure:

r sponsive automatically moves-"1a e valve ehambereasing sa d-ma fiee" commun cation dun-fig the ex-lialat 7 REFERENCES CITED:

me of this'bateht: y 7 e a UNITEDSTATES PATENTS,

N mb?! 7. 1 912 r o se ta 1-91 6 1,172,879 e 2 4 6 1,202,125 ,Tmlarhn' -f -a-e O 4 1 .6 mac w a, r 239 43 I' J--.---- M ly 44 6 -QTH R EFERENCES 1*?4 R $ifia f fipa ill ".i 9s. iggeis ig an; Anestnesmiogmvol. 14,"N'ov. I'Ma'pp; 608170 611-. ,7 j,

1 Thfr'oiiqwing referncesiar dfrecotaemir 'v chamber "in

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