US3045668A - Intermittent positive pressure respirator - Google Patents

Description

July 24, 1962 A. s. J. LEE 3,

INTERMITTENT POSITIVE PRESSURE RESPIRATOR Filed Jan. 20, 1959 Fig. I

INVENTOR. Arno/a 5. J. Lee

Merriam, Lora/l 8 Smith A 7'T0/P/VEY5 United States Patent 3,045,668 INTERMITTENT POSITIVE PREfiSURE RESIHKATOR Arnold S. J. Lee, Shrewsbury, N.J., assignor to Invengineering, Inc, Belmar, N.J., a corporation of New Jersey Filed Jan. 20, 1959, Ser. No. 787,862 12 Claims. (Cl. 12829) This invention is directed to artificial respiration. It is more specifically concerned with an intermittent positive pressure artificial respirator.

Because the chemical basis of life is essentially an oxidative process, respiration is a process common to all forms of animal life. Respiration consists essentially in the passage of oxygen from the air to the place where oxygen is used up by the body, and the transport of carbon dioxide from the place where it is produced to the external air. It is frequently necessary to utilize respiratory aids for surgical patients or others whose respiration has become immobilized. Individuals who are rendered apneic are artificially respired by respirators which are essentially pumps for pushing a breathing gas into a living thing in a more or less rhythmic manner and alternately allowing the lung contents to be exhaled. One of the preferred respirators is the intermittent positive pressure respirator which applies to the living thing interrnittent pulses of a respiratory gas at pressures above atmospheric and allow the patient to passively exhale at approximately atmospheric pressure during the intervals between the intermittent pulses. This type of respirator has several classes, viz., those which provide pressure limited inspiration and those which employ a constant inspiration flow rate.

According to this invention there is provided an intermittent positive pressure respirator which can be operated as a pressure limited type or a constant velocity inspiration type or which can be provided with actuating gas flow control means combining the preferred features of each of the aforesaid types.

FIGURE 1 is a schematic diagram of a complete specific embodiment of a respirator employing the various features of the instant invention and utilizing an actuating gas fiow control means combining the advantages of the pressure limited inspiration and constant inspiration flow rate methods.

FIGURE 2 is a cross sectional view of a specific pressure equalizing valve employed to control the inflow of breathing gas into the respirator of this invention.

Referring to the drawings, in FIGURE 1 the specific embodiment of an illustrative respirator which is shown schematically consists of an actuator circuit which provides the mechanical forces necessary to provide the cyclic action and pump the breathing gas into the patient and a patient breathing circuit which contains and processes the breathing gases. In the illustrative circuitry there is provided a gas inlet means 10. The gas which is used is a combined breathing gas and actuating gas, e.g. oxygen, introduced at a super atmospheric pressure, e.g. 35-60 p'.s.i.'g. and passed through a conventional air filter 11. Branch line 12 transports the gases from the inlet means to the actuating circuit. In branch line 12 there is provided a conventional pressure regulator for controlling the downstream pressure utilized for operating the various elements of the actuating circuit. This regulator is set to supply the actuating gas at a pressure of about psi. One portion of the gas supplied by branch line 12 is pased through conduit 14 to a conventional air motor 15. The flow of gas in this conduit is controlled by a suitable valve. In the illustrative embodiment a windshield wiper motor is employed as the compressed air motor. A cam 16 is mounted on the trans- 3,045,668 Patented July 24, 1962 mission shaft of the windshield wiper motor 15. The cam 16 controls the phasing of the actuator circuit during the inspiration phase and the expiration phase of a respiratory cycle. Inspiration-expiration time ratios of one-half to two-thirds are commonly employed and appropriate cams or other suitable timing devices provided. The other portion of the gas from branch line 12 passes through line 17 in which is installed sequentially an inspiration iiow rate control 18, e.g. a needle valve, and a maximum respiration pressure control 19, e.g. a low pressure regulator. By the use of the needle valve and low pressure regulator in series, for any given respiratory frequency it is possible to control the operation of the actuating circuit so that the pressure will rise at any given respiratory flow rate, reach a maximum, stay at this maximum pressure for any desired percentage of the inspiratory portion of the cycle, and then decrease during the exhalation phase of the respiratory cycle thereby combining the preferred features of the pressure limited inspiration and constant inspiration flow rate methods. The actuating gas stream leaves the maximum respiration pressure control 19 at a maximum pressure of about 0.8 p.s.i.g. and passes through line 21 to actuating valve 22 which controls the flow of actuating gas in and out of chamber 23. To control the flow of actuating gas into and from chamber 23 there is provided a reciprocating valve closure 24 which alternately engages ports 25 and 26 of valve 22. The reciprocating action is effected by means of valve :stem 27 which is journaled in bearing 28 disposed in the bore of port 26. At the distal end of valve stem 27 is provided a cam follower 29 which engages the cam surface of cam 16. Valve stem 27 is spring loaded in order to maintain the desired continuous engagement between cam follower 29 and the face of cam 16. A valve port 30 is provided to permit the flow of gas into and from chamber 23 to actuating valve 22. Chamber 23 is of rigid construction having an internal volume unaffected by the operating pressures employed during the use of the apparatus. Pendently mounted from the upper end wall of chamber 23 is a flexible bellows 31 which is actuated and compressed by the flow of gas from actuating valve 22 into chamber 23 to eifect the pumping of the breathing gas contained within the bellows. Bellows 31 is preferably of the sylphon type having corrugated side walls fabricated from a thin elastomeric material such as rubber. Bellows 31 is mounted within chamber 23 such that the interior thereof is isolated from the interior of chamber 23. A small weight 32, e.g. about one-half pound, is provided in the bottom of bellows 31 to effect its extension beyond its normal relaxed length and facilitate the return of the bellows 31 to its uncompressed state during the exhalation phase of the respiratory cycle. In the interior of bellows 31 there is also provided a pro-loaded bellows compression spring 33 which in the preferred embodiment is bound with a nylon cord to pre-load it so that it will exert a substantially constant one-half pound force against the bottom of the bellows when the bellows compresses sufficiently for the bottom to engage the spring. This spring functions in co-operation with a check valve in the patient breathing circuit opening to the atmosphere, which will be hereinafter discussed, when inadequate amounts of breathing gases are supplied to the system.

In order to permit the use of the respirator of this invention in conjunction with conventional anesthesia machines, a pressure equalizing valve 34 is utilized in order to prevent a rise in system pressure due to excess breathing gas addition when the respirator is so used. In the illustrative embodiment a rubber mushroom shaped pneumatic diaphragm 35 is employed as the valve closure. The interior of diaphragm 35 is connected with the interior of chamber 23 by means of passageway 36.

The interior of the bellows 31 communicates with the ambient atmosphere through valve port 37. The shape of the diaphragm makes its effective area greater than the area of the exhalation-port.

In order to observe the movement of bellows 31 for an estimation of the amount of breathing gas pumped into the patient the side walls 38 of chamber 23 are made of a transparent material of construction such as an acrylic resin, glass, or other suitable transparency. In order that the amount can be more closely approximated, a calibrated scale 39 is mounted on the inner face of the transparent sidewall.

The patient circuit consists of branch line 40 in which is placed a control valve 41, such as a needle valve, for controlling the supply of breathing gas to the patient. A pressure gauge 42 is also preferrably installed in line 40 in order to observe the operational pressures which are utilized in the respirator. Branch line 40 is connected to intake manifold 43. Mounted on manifold 43 is a conventional bladder type gas reservoir bag 44 into which the breathing gas is received prior to being transferred to bellows 31, during the exhalation phase of the respiratory cycle. A second pressure equalizing valve 45 which operates in cooperation with gas reservoir bag 44 to control the quantity of inflow of breathing gas is also installed on intake manifold 43. Passageway 46 is employed for delivering the gas pumped from the interior of bellows 31 into the patient. One end of line 46 terminates at the interior of bellows 31 and the other end is provided with a means for delivering the gas to the patient and/or an anesthesia machine. Intake manifold 43 is connected with line 46 by means of transfer line 47 in which is interposed a lightly loaded check valve which controls the flow from intake manifold 43 into line 46 but prevents the flow of gas from line 46 into intake manifold 43. Selector valve 49 is a three way valve utilized to permit the switching of the breathing gas flow in line 46* and permit it to be either pumped from the bellows 31 when in the position as shown or, upon repositioning, directly from the interior of the reservoir bag 44. A pressure relief valve 50, preferably pre-set to 25 mm. Hg and which has no means for closing it or? is utilized in line 46. In the event that a higher operating pressure is required additional weights can be employed which are manually added to the pressure relief valve in order to raise the pressure at which the valve will open to 40mm. Hg. To observe the pressure of the breathing gas directed into the patient, a pressure gauge 51 is installed in line 46.

In order to improve the flexibility of the respirator of this invention, several additional fittings are preferably mounted on intake manifold 43. Gas mixture inlet port 52 is used where it is desired to employ the mixing of several gases to form the breathing gas mixture and emergency room air intake check valve 53 is employed in order to supply the patient with room air if the supply of breathing gases to the respirator is inadequate. The emergency room air intake check valve 53 is also operative during spontaneous breathing. Air inlet check valve 53 operates in conjunction with bellows spring 33 when inadequate amounts of breathing gases are supplied to the system. In this instance the bottom of the bellows will rise as the volume of breathing gas in the system is reduced. When the bottom of the bellows rises far enough to compress the bellows spring the negative pressure created within the bellows during the subsequent exhalation phase of the respirator is sufliciently great to lift the weighted check valve 53 from its seat and thereby permit air to enter the system. The closure of check valve 53 is so loaded (with due consideration to the area of its valve seat) that the negative pressure generated by the bellows and its weight alone is inadequate to lift it from its seat.

There is also provided a room air inlet port 54 which can be employed in the event that room air is to be 1. utilized as a breathing gas. Gas mixture inlet port 52 and room air inlet port 54 are respectively provided with removable closures which can be easily removed to permit the use of these ports for the supply of a suitable breathing gas mixture.

In operation of the respirator a source of actuating compressed gas at a pressure within the range of about 35-60 p.s.i. is connected to gas inlet 10. In the illustrative embodiment a single gas, viz. oxygen, is employed as the actuating gas and the breathing gas. Pressure regulator 13 in branch line 12 is regulated to provide a downstream pressure of about 20 p.s.i. Control valve 57 which controls the flow of actuating gas to compressed .air motor 15 is regulated to efiect the desired frequency of the respiration cycle. Generally this is controlled within the range of 10 to 40 cycles per minute. The portion of the actuating gas which operates bellows 31 is delivered through lines 17 and 21 through actuating valve into the interior of chamber 23. During the rise of pressure in the inspiration phase, at any pressure below the setting of the maximum respiration pressure control 19, the inspiration flow rate is relatively constant. When the pressure reaches the setting of the low pressure regulator 19, all inspiration ceases immediately. If the low pressure regulator is set at some very high value, higher than any pressure the particular patient under treatment will require, then the apparatus has its flow rate determined by the setting of inspiration flow rate control 18, and the equivalent of a constant velocity inspiration method is effected with the exception that under no circumstances can the pressure to the actuating valve, and therefore in any other part of the apparatus, rise above the preferred 0.8 p.s.i.g. maximum setting of the low pressure regulator. In this embodiment, since the pressure to the actuating valve never rises above 0.8 p.s.i., the actuating valve has only this 0.8 p.s.i. to cut off.

If the inspiration fiow rate control 18 is opened all the way, the apparatus becomes a pressure limited inspiration type. The pressure will rise rather quickly during inspiration to a maximum as set by the low pressure reguator.

As mentioned above, by the use of both the needle valve and the low pressure regulator in series, it is possible, for any given respiratory frequency, to set the apparatus so that the pressure will rise at any given inspiratory flow rate, reach a maximum, stay at this maximum pressure for any desired percentage of the cycle and then fall off in the exhalation phase as previously.

During the inspiration phase, the actuating gas at some pressure above atmospheric is delivered into chamber 23 and closes the pressure equalizing valve 34. During this phase valve closure 24 is seated against valve port 26 permitting the flow of the gas from the actuating valve into the chamber 23. This forces bellows 3*1 upwardly and pushes or pumps the contents of bellows 31 into the pat ent. The maximum pressure attainable in the bellowspatient system is the pressure in chamber 23 minus the pressure required to hold the bellows in a compressed position. With the preferred type of sylphon bellows this pressure differential is approximately 2 mm. Hg.

During the expiration phase of the respiratory cycle valve closure 24 is moved into engagement with valve port 25. In this position the interior of chamber 23 is connected directly to the atmosphere through valve port 26 which exhausts to the atmosphere. Accordingly the pressure inside the bellows 31 decreases to atmospheric or slightly less and the patient is permitted to exhale by a subsidiary valving system. A suitable valve which can be used for this purpose is a non-rebreathing valve described and claimed in the co-pending application Serial No. 752,664 filed August 1, 1958, of Arnold S. J. Lee.

When the illustrative respirator is employed in a nonrebreathing system breathing gas may be supplied from gas inlet 10. In order to introduce the breathing gas into the intake manifold 43 flow control valve 41 is in a partially open position. With valve 41 open the breathing gas supply can travel to the reservoir bag 44; or through check valve 48 to bellows 31 only during the exhalation phase of the respirator cycle. During this phase of the cycle weighted bellows 32 withdraws the breathing gas from reservoir bag 44 through check valve 48. During the inspiration phase of the respirator cycle the breathing gas will travel only to reservoir bag 44 which is maintained at a very slight super atmospheric pressure, e.g. about 1 mm. Hg and held at that pressure by a suitable pressure equalizing valve 45.

This arrangement produces a situation where all of the breathing gas received by the patient is pumped by and from bellows 31 thus allowing observation of the bellows movement for estimation of the amount of gas pumped into the patient. Of course, depending upon the maximum inspiration pressure during any cycle as well as the volume and expansibility of the system as a whole there will be a certain bellows movement even if the patient should receive no oxygen at all. In practice this is observed by closing oif the system at the patient connection and observing the bellows movement as a function of the maximum inspirational pressure. If the inlet breathing gas were supplied directly to the bellows some of the gas supplied to the patient would flow directly during inspiration and not be indicated by the movement of the bellows. It is therefore preferred to utilize the intermittent positive pressure respirator of this invention in conjunction with a reservoir bag in order that the respirator of this invention can be efliciently employed.

As indicated above emergency air inlet port 53 provides a means whereby the patient can be supplied with room air if the supply of the breathing gas to the respirator is inadequate. Where no breathing gas is introduced into the intake manifold 43 through inlet means the respirator will use room air. In this instance the weight in the bottom of the bellows plus the weight of the bellows itself produces a negative pressure within the bellows during the exhalation part of the respirator cycle to effect the intake of room air through the intake manifold into the bellows for transfer to the patient.

By the use of selector valve 49 provisions are made which permit the use of the respirator during the course of any particular use of the equipment when at least for part of the time the patient will breathe spontaneously or will require manual control by the operator of the machine. Selector valve 49 is a valve means which permits the gas flow to be swiftly switched to connect the patient either to the respirator or to reservoir bag 44. The patient can breathe spontaneously from the reservoir bag or can receive intermittent positive pressure breathing by manually squeezing the reservoir bag.

In employing the instant invention as a non-rebreathing system component it is preferred that the system be operated with the inflow of breathing gas distinctly greater than the outflow to the patient. Even though a nonrebreathing face valve allows for room air to be inspired in the event that the inflow of breathing gas is less than the outflow, this reduces the efficiency of the respirator because the respired gas will be a mixture of room air and the breathing gas mixture being supplied.

In order to maintain a sufficient supply of breathing gas in reservoir bag 44 some provision should preferably be made to maintain the reservoir bag inflated at a pressure, e.g. l Hg, which would be satisfactory to maintain an inflated reservoir bag but which would prevent over-distention of the bag. A simple relief valve is unsatisfactory because it would discharge the breathing gas to the atmosphere instead of to the patient when intermittent positive pressure exists. In order to obviate this problem and provide a suitable pressure equalizing valve which distinguishes between the pressure build-up from excessive gas flow into the system and pressure rise due to the intermittent positive pressure breathing a 6 valve 45 is utilized in the intake manifold of the patient circuit.

A specific embodiment of a suitable pressure equalizing valve is illustrated in FIGURE 2. This valve consists of a valve body 60 having an inner chamber 61 which is provided with an upper seat 62 and a lower seat 63. A valve closure 64 is biased into a normally closed position on seat 63 by means of a suitable biasing member such as spring 65. The valve closure 64 is a square shaped piece of rigid sheeting, preferably Teflon or Mylar. With valve closure 64 in the normally closed position this closes inlet port 65 which communicates with the interior of intake manifold 43. Outlet port 67 connects the interior of valve body 61 to the atmosphere. Because it is possible to seal off upper seat 62 inadvertently if the pressure rise within intake manifold 43 at any time is rapid, especially if the excess rate of gas inflow is high, as a safety feature a metal plunger 68 which can be operated by toggle handle 69 which is suitably journalled in valve body 61 and spring loaded to facilitate its operation is provided. Closure 64 is free to rise and fall between lower seat 63 and upper seat 62. The valve closure moves within an intermediate chamber only slightly larger in diameter than the diagonal of the square valve closure. Valve seat 63 communicates with inlet port 66 which is connected in the breathing gas circuit in the intake manifold preferably near reservoir bag 44. Valve seat 62 is open to the atmosphere. The valve closure which is very light in weight, e.g. 2.9 grams, is such that the pressure required to lift it from seat 63 which in a prefer-red embodiment has a diameter of .625 inch, is the minimum necessary to keep the reservoir bag 44 reasonably inflated at a pressure of 1 mm. Hg. When the patient respires spontaneously and an excess flow of gas is admitted into the system the smooth outflow of the excess gas lifts the valve closure slightly oif seat 63. This allows the excess gas to discharge to the atmosphere through outlet port 67 and prevents over-distention of the bag. If the reservoir bag 44 however is rapidly compressed as during intermittent positive pressure breathing, the momentary high velocity of the escaping gas lifts the flapper valve against seat 62 sealing it off from the atmosphere. In order to prevent the inadvertent seating of valve closure 64 against upper seat 62 metal plunger 68 which is controlled by toggle handle 69 is depressed thereby below the face of upper seat 62 in order to prevent valve closure 64 from seating against upper seat 62. When toggle handle 69 is extended upawrd the valve will allow positive pressure respiration. When toggle handle 69 is depressed the pressure cannot be built up under any circumstances and the valve can safely be left untended.

The illustrative embodiment of this invention provides a flexible respirator which can be utilized in a variety of services. The apparatus of this. invention can be employed for pure oxygen, room air, or other oxygen enriched room air respiration without any accessory equip ment other than a non-rebreathing valve face mask. In a non-rebreathing system the respirator is employed in conjunction with a conventional anesthesia machine or vaporizer. In this application the respirator together with a non-rebreathing valve provides all the special valving and other features required for a sound non-rebreathing system; spontaneous breathing, manually-controlled intermittent positive pressure, automatic intermittent positive pressure. When the instant invention is employed in a circle system in conjunction with an ordinary or conventional anesthesia machine the circle system is enhanced in safety by the action of the pressure equalizing valves utilized in the preferred specific embodiment. These pre vent any increase in pressure in the system during spontanous breathing or during the exhalation phase of intermittent positive pressure breathing (manually or automatic). In a circle system of this nature because an ordinary reservoir bag of conductive rubber requires approximately 1 mm. Hg pressure to keep it reasonably inflated, the patient exhales against a positive pressure of 1 mm. Hg in addition to the resistance of the CO absorbant, the exhalation check valve and the pneumatic channels of the system. Because the bellows is weighted so that it tends to produce a 1 mm. Hg sub-atmospheric pressure during the exhalation phase the final effect of the respirator is to lower the exhalation resistance by approximately 2 mm. Hg during the major part of the exhalation phase.

In constructing the respirator of this invention conventional materials of construction, other than those specifically noted above, can be utilized. In the construction of the various elements of the respirator it is preferred that high strength aluminum alloys be utilized in the fabrication of components requiring metal materials of construction. The reservoir bag and bellows is preferably fabricated from a conductive rubber. The volume of each of these elements depends upon the lung capacity of the patient upon which the apparatus is being used. For example, if the respirator is being employed for pediatric work a bellows having a smaller diameter will be utilized to replace the standard size bellows which is calibrated in terms of lung capacity of adults.

Although the instant invention is specifically illustrated by the embodiment hereinbefore described, it is apparent that various modifications in the design of the apparatus will be obvious to those skilled in the art to which the instant invention pertains. It is apparent, for example, that in the operation of the actuating circuit the mechanical action of the actuating valve can be effected by means other than the illustrative compressed air motor (windshield wiper motor). For example, a fractional horsepower electric motor can be linked to the actuating valve by a motor valve linkage which will effect the desired reciprocation of the valve stem to provide the inspirationexpiration time ratios of /2-- /s which are commonly employed. It is also to be noted that the pre-loading of the bellows compression spring can be effected by other means than those specifically illustrated wherein the spring is bound with a nylon cord to pre-compress it sufliciently such that a force of /2 lb. is required to cause it to begin to compress. Conventional check valves and safety valves can also be utilized in assembling the instant invention which will provide a desired relief pressure.

Although the actuating gas control shown in the illustrative embodiment is preferred, other control means can be used to effect the aforementioned respiration methods. In the pressure limited inspiration method the flow of actuating gas in branch line 17 is directed through line 17 through a low pressure regulator which is adjusted to provide a downstream pressuer within the range of about -40 mm. Hg. Because of the inherent limitations on low pressure regulators the output pressure of the respirator during inspiration assumes a saw-tooth wave form. Although theoretically this should be a square wave form, in practice the output of the regulator is such that the wave form assumes a saw-tooth form having a convexly upward configuration. If the respirator is to be employed as a constant inspiration flow rate type, an inspirator needle valve is utilized in place of the pressure regulator to control the flow of compressed actuating gas from line 17 through line 21 into actuating valve 22. When employing the respirator of this invention in constant inspiration flow rate method the flow of gas into chamber 23 and therefore the flow of gas out of bellows 31 into the patients system is constant during the inspiration part of the cycle. This is accomplished by the setting of the needle valve across which there is a relatively large and constant drop in pressure (20 p.s.i.g. to breathing pressure which is /2 p.s.i.g. maximum). During the inspiration phase of the respiration cycle therefore a constant fiow of gas enters chamber 23. This system puts out a gas pressure curve which is a true saw-tooth and has the of the patient when the rate of respiration is changed.

Accordingly it is intended that the scope of the subject invention be limited only in the manner as defined in the appended claims.

What is claimed is:

1. An intermittent positive pressure respirator comprising a gas inlet means for supplying an actuating gas; an enclosed gas chamber having an inlet means; a timecycled actuating valve means connected to said inlet, said valve means alternatively and automatically connecting the interior of said chamber with said gas inlet means and directly with the exterior of said chamber in phase respectively with the inhalation and exhalation phases of a respiratory cycle; a flexible bellows pendently mounted within said chamber, said bellows being compressed by the flow of an actuating gas into said chamber during the inhalation phase of the respiratory cycle; a preloaded resilient means mounted within said bellows adjacent the proximal end thereof; means for supplying a breathing gas to the interior of said bellows; a passageway communicating with the interior of said bellows at one end thereof and terminating in an outlet for said breathing gas; and a check valve means positioned in said passageway connecting the interior of said passageway with the ambient atmosphere and permitting the one way flow of air from said atmosphere into said passageway, said resilient means being adapted to urge said bellows into an expanded position and produce a subatmospheric pressure within said bellows to unseal said check valve means and permit the flow of air into said passageway.

2. In an intermittent positive pressure respirator an actuating circuit comprising a gas inlet means for supplying an actuating gas, enclosed gas chamber having an inlet means, a timecycled actuating valve means connected to said inlet, said valve means alternatively and automatically connecting the interior of said chamber with said gas inlet means and directly with the exterior of said chamber in phase respectively with the inhalation and exhalation phases of a respiratory cycle, a flexible bellows pendently mounted within said chamber, said bellows being compressed by the flow of an actuating gas into said chamber during the inhalation phase of the respiratory cycle; and a patient breathing circuit comprising a manifold, means for supplying a breathing gas to said manifold, an elastic bladder, gas reservoir connected to said manifold for supplying a breathing gas to said bellows, a passageway communicating with the interior of said bellows at one end thereof and terminating in an outlet for said breathing gas, a transfer line connecting said passageway and said manifold, and check valve means positioned in said transfer line to control the one way flow of breathing gas from said manifold into said passageway.

3. In a respirator in accordance with claim 2, in said patient breathing circuit a pressure equalizing valve means connected to said manifold adjacent said gas reservoir to prevent a rise in pressure in said breathing circuit during the exhalation phase of the respiratory cycle due to excess breathing gas addition.

4. In a respirator in accordance with claim 3 which comprises a valve body having an inlet port communicating with said manifold and an outlet port open to the ambient atmosphere, an inner chamber intermediate said inlet and outlet ports having a first valve seat positioned adjacent said outlet port and a second valve seat positioned adjacent said inlet port vis-a-vis said first seat, a valve closure biased in a normally closed position against said second seat.

5. In an intermittent positive pressure respirator an actuating circuit comprising a gas inlet means for supplyng an actuating gas, an enclosed gas chamber having an inlet means, a time-cycled actuating valve means connected to said inlet, said valve means alternatively and automatically connecting the interior of said chamber with said gas inlet means and directly with the exterior of said chamber in phase respectively with the inhalation and exhalation phases of a respiratory cycle, a flexible bellows pendently mounted within said chamber, said bellows being compressed by the flow of an actuating gas into said chamber during the inhalation phase of the respiratory cycle, means for urging said bellows into at least a partially expanded position to resist deflation of said bellows; and a patient breathing circuit comprising a manifold, means for supplying a breathing ga to said manifold, an elastic bladder, gas reservoir connected to said manifold for supplying a breathing gas to said bellows, a passageway communicating with the interior of said bellows at one end thereof and terminating in an outlet for delivering said breathing gas to a patient, a first check valve means positioned in said manifold connecting the interior of said manifold with the ambient atmosphere and permitting the one way flow of air from said atmosphere into said manifold, said urging means being adapted to urge said bellows into an expanded position and produce a subatmospheric pressure within said bellows to unseal said check valve means and permit the flow of air into said manifold, a transfer line connecting said passageway and said manifold, and a second check valve means positioned in said transfer line to control the one way flow of breathing gas from said manifold into said passageway.

6. In a respirator in accordance with claim 5, in said patient breathing circuit a pressure equalizing valve means connected to said manifold adjacent said gas reservoir to prevent a rise in pressure in said breathing circuit during the exhalation phase of the respiratory cycle due to excess breathing gas addition.

7. In a respirator in accordance with claim 6 which comprises a valve body having an inlet port communicating with said manifold and an outlet port open to the ambient atmosphere, an inner chamber intermediate said inlet and outlet ports having a first valve seat positioned adjacent said outlet port and a second valve seat positioned adjacent said inlet port vis-a-vis said first seat, a valve closure biased in a normally closed position against said second seat.

8. In an intermittent positive pressure respirator an actuator circuit comprising a gas inlet means for supplying an actuating gas, an enclosed gas chamber having an inlet means, a time-cycled actuating valve means connected to said inlet, said valve means alternatively and automatically connecting the interior of said chamber with said gas inlet means and directly with the exterior of said chamber in phase respectively with the inhalation and exhalation phases of a respiratory cycle, actuating gas flow control means cooperating with said gas inlet means comprising an inspiration flow rate control means and a maximum respiration pressure control serially connected between said gas inlet means and said actuating valve, a flexible bellows pendently mounted within said chamber, said bellows being compressed by the flow of an actuating gas into said chamber during the inhalation phase of the respiratory cycle, means for urging said bellows into at least a partially expanded position to resist deflation of said bellows; and a patient breathing circuit comprising a manifold, means for supplying a breathing gas to said manifold, an elastic bladder, gas reservoir connected to said manifold for supplying a breathing gas to said bellows, a passageway communicating with the interior of said bellows at one end thereof and terminating in an outlet for delivering said breathing gas to a patient, a first check valve means positioned in said manifold connecting the interior of said manifold with the ambient atmosphere and permitting the one way flow of air from said atmosphere into said manifold, said urging means being adapted to urge said bellows into an expanded position and produce a subatmospheric pressure within said bellows to unseal said check valve means and permit the flow of air into said manifold, a transfer line conmeeting said passageway and said manifold, and a second check valve means positioned in said transfer line to control the one way flow of breathing gas from said manifold into said passageway.

9. In an intermittent positive pressure respirator an actuating circuit comprising a gas inlet means for supplying an actuating gas, an enclosed gas chamber having an inlet means, a time-cycled three way actuating valve means interconnecting a first part connected to the gas inlet means, a second part connected to the inlet means in said chamber, and a third part connecitng with the exterior of said chamber, a valve closure cooperating with said first and third parts, means operated by said actuating gas for positioning said valve closure whereby the interior of said chamber is alternatively and automatically connected with said gas inlet means and directly with the exterior of said chamber in phase respectively with the inhalation and exhalation phases of a respiratory cycle, actuating gas flow control means cooperating with said gas inlet means comprising an inspiration flow rate control means and a maximum respiration pressure control serially connected between said gas inlet means and said actuating valve, a flexible bellows pendently mounted within said chamber, said bellows being compressed by the flow of an actuating gas into said chamber during the inhalation phase of the respiratory cycle, means for urging said bellows into at least a partially expanded position to resist deflation of said bellows and a patient breathing circuit comprising a manifold, means for supplying a breathing gas to said manifold, an elastic bladder, gas reservoir connected to said manifold for supplying a breathing gas to said bellows, a passageway communicating with the interior of said bellows at one end thereof and terminating in an outlet for delivering said breathing gas to a patient, a first check valve means positioned in said manifold connecting the interior of said manifold with the ambient atmosphere and permitting the one way flow of air from said atmosphere into said manifold, said urging means being adapted to urge said bellows into an expanded position and produce a subatmospheric pressure within said bellows to unseal said check valve means and permit the flow of air into said manifold, a transfer line connecting said passageway and said manifold, and a second check valve means positioned in said transfer line to control the one way flow of breathing gas from said manifold into said passageway.

10. In an intermittent positive pressure respirator an actuating circuit comprising a gas inlet means for supplying an actuating gas, an enclosed gas chamber having an inlet means, a time-cycled three way actuating valve means interconnecting a first part connected to the gas inlet means, a second part connected to the inlet means in said chamber, and a third part connecting with the exterior of said chamber, a valve closure cooperating with said first and third parts, means operated by said actuating gas for positioning said valve closure whereby the interior of said chamber is alternatively and automatically connected with said gas inlet means and directly with the exterior of said chamber in phase respectively with the inhalation and exhalation phases of a respiratory cycle, actuating gas flow control means cooperating with said gas inlet means comprising an inspiration flow rate control means and a maximum respiration pressure control serially connected between said gas inlet means and said actuating valve, a flexible bellows pendently mounted Within said chamber, said bellows being compressed by the flow of an actuating gas into said chamber during the inhalation phase of the respiratory cycle, means for urging said bellows into at least a partially expanded position to resist deflation of said bellows; and a patient breathing circuit comprising a manifold, means for supplying a breathing gas to said manifold, an elastic bladder, gas reservoir connected to said manifold for supplying a breathing gas to said bellows, a passageway communicating with the interior of said bellows at one end thereof and terminating in an outlet for delivering said breathing gas to a patient, a first check valve means positioned in said manifold connecting the interior of said manifold with the ambient atmosphere and permitting the one way flow of air from said atmosphere into said manifold, said urging means being adapted to urge said bellows into an expanded position and produce a subatmospheric pressure within said bellows to unseal said check valve means and permit the flow of air into said manifold, a first transfer line connecting said passageway and said manifold, a second check valve means positioned in said transfer line to control the one way flow of breathing gas from said manifold into said passageway, a second transfer line connecting said manifold and said passageway, and a selector valve for selectively directing the flow of breathing gas directly through said manifold and said passageway to said outlet for delivering the breathing gas to a patient and directing the flow of breathing gas directly from said bellows through said passageway to said outlet.

11. In an intermittent positive pressure respirator an actuator circuit comprising a gas inlet means for supplying an actuating gas, an enclosed gas chamber having an inlet means, a time-cycled three way actuating valve means interconnecting a first part connected to the gas inlet, a second part connected to the inlet means in said chamber, and a third part connecting with the exterior of said chamber, a valve closure cooperating with said first and third parts, means operated by said actuating gas for positioning said valve closure whereby the interior of said chamber is alternatively and automatically connected with said gas inlet means and directly with the exterior of said chamber in phase respectively with the inhalation and exhalation phases of a respiratory cycle which comprises a valve stem secured to said valve closure and reciprocatively journalled in said actuating valve means, a windshield wiper motor having a driven shaft, a cam means driven by said shaft adapted to reciprocatively move said valve stem, an actuating gas control means cooperating with said gas inlet means comprising an inspiration flow rate control means and a maximum respiration pressure control serially connected between said gas inlet means and said actuating valve, a flexible bellows pendently mounted within said chamber, said bellows being compressed by the flow of an actuating gas into said chamber during the inhalation phase of the respiratory cycle, means for urging said bellows into at least a partially expanded position to resist deflation of said bellows; and a patient breathing circuit comprising a manifold, means for supplying a breathing gas to said manifold, an elastic bladder, gas reservoir connected to said manifold for supplying a breathing gas to said bellows, a pressure equalizing valve mounted on said manifold to permit any excess breathing gas supply to be dissipated to the atmosphere without interfering with positive pressure inspiration, said equalizing valve compris ing a valve body having an inlet port communicating with said manifold, and an outlet port open to the ambient atmosphere, an inner chamber intermediate said inlet and outlet ports having a first valve seat positioned adjacent said outlet port and a second valve seat positioned adjacent said inlet port vis-a-vis said first seat, a valve closure biased in a normally closed position against said second seat, a passageway communicating with the interior of said bellows at one end thereof and terminating in an outlet for delivering said breathing gas to a patient, a first check valve means positioned in said manifold connecting the interior of said manifold with the ambient atmosphere and permitting the one way flow of air from said atmosphere into said manifold, said urging means being adapted to urge said bellows into an expanded position and produce a subatmospheric pressure within said bellows to unseal said check valve means and permit the flow of air into said manifold, a first transfer line connecting said passageway and said manifold, and a second check valve means positioned in said first transfer line to control the one way flow of breathing gas from said manifold into said passageway.

12. An intermittent positive pressure respirator comprising a gas inlet means for supplying an actuating gas; an enclosed gas chamber having an inlet means; a timecycled actuating valve means connected to said inlet, said valve means alternatively and automatically connecting the interior of said chamber with said gas inlet means and directly with the exterior of said chamber in phase re spectively with the inhalation and exhalation phases of a respiratory cycle; a flexible bellows pendently mounted Within said chamber, said bellows being compressed by the flow of an actuating gas into said chamber during the inhalation phase of the respiratory cycle; means for urging said bellows into at least a partially expanded position to resist deflation of said bellows; means for supplying a breathing gas to the interior of said bellows; a passageway communicating with the interior of said bellows at one end thereof and terminating in an outlet for said breathing gas; and a check valve means positioned in said passageway connecting the interior of said passageway with the ambient atmosphere and permitting the one way flow of air from said atmosphere into said passageway, said urging means being adapted to urge said bellows into an expanded position and produce a subatmospheric pressure within said bellows to unseal said check valve means and permit the flow of air into said passageway.

References Cited in the file of this patent UNITED STATES PATENTS 2,284,964 Mautz June 2, 1942 2,737,176 Fox Mar. 6, 1956 FOREIGN PATENTS 1,015,863 France Aug. 13, 1952 946,258 Germany July 26, 1956

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