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Publication numberUS2391877 A
Publication typeGrant
Publication dateJan 1, 1946
Filing dateNov 29, 1943
Priority dateNov 29, 1943
Publication numberUS 2391877 A, US 2391877A, US-A-2391877, US2391877 A, US2391877A
InventorsCahan Alvin M
Original AssigneeCahan Alvin M
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Respiration apparatus
US 2391877 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

Jan. 1, 1946.

A. M. CAHAN RESPIRATION APPARATUS "Filed NOV. 29, 1943 2 Sheets-Sheet-l Jan. 1, 1946. A. M. CAHAN RESPIRATION APPARATUS Filed Nov. 29, 1943 2 Sheets-Sheet 2 EQRNTMQQKW IN VENTOR N M. cAH4/V ,4770AIVEX) Patented Jan. 1, 1946 UNITED STATES PATENT OFFICE (Granted under the act of March 3, 1883,15

amended April 30, 1928; 3'70 0. G. 757) Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to respiration apparatus adapted to deliver oxygen or other gas to a persons lungs and to effect discharge of such gas from the persons lungs to the atmosphere.

An object of the invention is to provide respiration apparatus of the type referred to which is capable of functioning as a spontaneous demand breather to supply oxygen to a persons lungs and effect discharge of gas from the persons lungs to the atmosphere in accordance with the requirements of a spontaneously breathing person, and also capable of functioning as a resuscitator to establish and/or maintain artificial respiration in a non-breathing person or in a person whose spontaneous breathing rate has declined to a dangerous point.

Another object of the invention is to provide such apparatus which will automatically function either as a demand breather or as a resuscitator, depending upon and responsive to the condition of the users spontaneous breathing or lack of spontaneous breathing.

Another object of the invention is to provide such apparatus which will function automatically as a demand breather whenever the person using the same is breathing spontaneously at arespiration rate adequate to maintain useful consciousness and which will automatically function as a resuscitator to establish or maintain artificial respiration whenever the users spontaneous respiration rate declines to the dangerous point.

Another object of the invention is to provide such apparatus which is capable of functioning as a demand breather and also capable of functioning as a resuscitator without the use of a negative pressure phase in the respiratory cycle.

Another object of the invention is to provide such apparatus which is capable or automatically following the respiratory rhythm of the user with absolute fidelity whenever the spontaneous respiration rate is sufficient to maintain useful consciousness and which is capable of automatically establishing or maintaining artificial respiration at a predetermined respiration rate whenever the users spontaneous respiration rate declines to the dangerous point.

Another object of the invention is to provide such apparatus which is capabl of functioning automatically to deliver oxygen or other gas to a persons lungs and to eifect discharge of such gas therefrom in a regular and continuous artificial respiration cycle comprising alternate inhalation (delivery) and exhalation (discharge) phases at a predetermined minimum rateof successive occurrences of these respiratory phases, whenever the users spontaneous respiration rate does not exceed said predetermined rate, and which is capable of automatically functioning to deliver oxygen to a. persons lungs and of effecting discharge therefrom in accordance with the users spontaneous breathing requirements whenever his spontaneous, respiration rate exceeds said predetermined minimum rate.

Another object of the invention is to provide such apparatus which shall be suitable for use as a spontaneous demand breather for flying personnel requiring additional oxygen at high a1- titudes.

Another object of the invention is to provide such apparatus which shall .be suitable for the resuscitation of flying personnel separated from their oxygen supply through accident or enemy action.

Another object of the invention is to provide such apparatus that is not only satisfactory for conventional resuscitation purposes but is also satisfactory, for the treatment of patients in pulmonary edema following exposure to gaseous lung irritants such as phosgene or the like.

Another object of the invention is to provide such apparatus which is capable of maintaining and/ or establishing artificial respiration to thereby maintain useiul consciousness at altitudes above the ceiling limit of operation of conventional demand flow oxygen systems now in use.

An instrument capable of performing under these varied conditions outlined in the objects above stated must be provided with delivery and expiration fiow rates of oxygen or other gas delivered to and. expelled from the subject using the device that are automatically variable according to the particular requirements of the subject at any given time, in addition to providing for absolute control of the upper and lower limits of pressure under which the oxygen or other gas is delivered to the subject. Thus, during the inspiratory cycle the instrument must be capable of delivering oxygen or other gas to the subject under positive pressure up to a predetermined pressure limit in such a mannerthat should the subject demand an instantaneous flow of eighty-five to a hundred liters of gas per minute he shall have it Without fighting for it against a negative pressure; and should the subject in the next moment demand oxygen at a rate of five liters per minute, he shall have. it withthe device for the commencement of the inhalation cycle before the subject requires it.

In addition, the device must be capable of following the respiratory rhythm of the subject with absolute fidelity so as not to impose a rhythm of its own upon him, and yet should he cease to breathe, it must furnish him intermittent positive-pressure resuscitation automatically and without change in adjustment of the apparatus, and independently of altitude.

Theconventional type of resuscitator utilizes a positive-pressure phase followed by a negativepressure phrase in the respiratory cycle; that is to say the conventional type of resuscitator supplies oxygen or other gas to the persons lungs at a positive pressure and then withdraws said gas from the person's lungs by a sucking action or negative pressure phase. The most important reason for not using anegative-pressure phase at high altitude, in addition to other reasons based on physiological considerations, is that during a negative-pressure phase the partial pressure of oxygen in the rarefied atmosphere is,reduced below the ambient partial pressure. The result is that the blood saturation at that altitude is reduced below the level which would prevail ifthe oxygen were breathed under normal circumstances.

It has been found that, by breathing oxygen under intermittent positive pressure without the interposition of a negative pressure phase, it is possible to maintain useful consciousness comfortably at altitudes approximately up to fifty thousand feet. This is not possible with the use 01' a conventional demand oxygen flow system since the latter operates efliciently only when using a negative phase in the cycle.

In carrying the invention into practice, a conduit is provided for communication with the tracheal passage of a person and said conduit is provided with an intake port adapted for communication with a-source of supply of oxygen or other gas and said conduit is also provided with an exhaust portv communicating with the atmosphere. The intake and exhaust ports are equipped with valves associated in such a manner that when one valve is open the other is closed; i. e. when"the intake port is open to the source of supply to permit delivery of gas to a persons lungs, the exhaust port is closed to the atmosphere to prevent discharge of oxygen from the system, and also, when the intake port is closed to the source of supply to prevent delivery of gas to the lungs, the exhaust port is open to the atmosphere to permit discharge of the gas from the persons lungs. Pressure responsive means is provided responsive to pressure of gas in the system between the intake port and the main exhaust port to the atmosphere for controlling the operation of the main intake and exhaust valves aforesaid so that when the pressure within the system reaches a predetermined minimum level, the apparatus'is conditioned for the inhalation phase of the respiratory cycle in which the main intake port is open to the source of supply of oxygen for delivery of oxygen to the lungs of the user and the main exhaust port is closed to prevent discharge of gas from the lungs of the user and from the system to the atmosphere; and when the pressure in the system reaches a predetermined maximum level the device is conditioned for the exhalation phase of the respiratory cycle in which the main intake port is closed to the source of supply of oxygen prevent-- ing further delivery of oxygen to the lungs of the user and the main exhaust port is open to the atmosphere permitting discharge of gas from the lungs of the user and from the system to the atmosphere. Means is provided for adjusting the maximum and minimum pressure levels at which the respective delivery and exhaust means become effective.

A particular object of the invention is to provide control means for controlling the flow of gas to the users lungs which is operative to automatically vary the rate of flow in accordance with the users demand and operative to deliver gas to the users lungs at pressures above atmospheric pressure.

Another particular object of the invention is to provide control means for controlling the flow of gas to the users lungs which is operative to automatically vary the rate of flow in accordance with the users demand and which is adjustable to preselect the pressure range within which the control means is operative to cause flow of gas to the users lungs.

To the foregoing ends, the delivery flow control means of the invention is designed to operate responsive to variations in pressure within the users lungs and to vary the rate or flow of gas to the users lungs in a reciprocal relation to said pressure. Thus when the delivery means is effective, the flow of gas to the users lungs will be controlled by the delivery control means so that the flow is greatest when the pressure within the users lungs is at a minimum value and the flow will decrease as the pressure in the lungs rises. Means is provided for rendering the control means capable of causing how of gas to the users lungs when the pressures therein are above the atmospheric pressure. Means is also provided for adjusting the range of pressures at which the control means may operate to cause flow of gas to the users lungs.

Another particular object of the invention is to provide control means for controlling the discharge flow of gas from the users lungs to the atmosphere which is capable of affording a predetermined constant positive pressure opposing exhalation while at the same time permitting varying rates of exhalation, according to the users requirements, and allowing the pressure within the respiratory channels to reach the ambient atmosphere pressure within a predetermined maximum period.

In accordance with the invention, discharge control means is provided for controlling the discharge of gas from the users lungs to the atmosphere during the exhalation phase of the apparatus, said discharge control means including means for varying the rate of discharge of gas from the respiratory channels as a function of the instantaneous pressure of gas within said channels when said pressure is within predetermined limits, and means for effecting discharge of gas from the respiratory channels irrespective of saidpressure limits. Provision is made for the adjustment of the pressure limits within which the first means may operate. Provision is also made for adjusting the discharge effectiveness of the second means.

The present invention contemplates improvements in the type of apparatus disclosed in my United States Patent No. 2,288,436, dated June 30, 1942, the present invention relating primarily to the control of the delivery and discharge of gas in connection with this type of apparatus.

Other objects, advantages and features of novelty will become apparent as the invention is described in detail in connection with the accompanying drawings, in which,

Fig. l is a partially schematic, partially sectional view of a respiration apparatus illustrating the principles of the present invention;

Fig. 2 is a pressure flowdiagrarn showing the pressure pattern of successive respiration cycles of said apparatus as they occur under the condition of normal respiration of a breathing person and also as they occur in artificial respiration of a nonbreathing person, said diagram also illustrating the relation between the inspiratory flow and the pressure of gas within the user's lungs.

Description of the respiration cycling instrumentalities Now referring to the drawings for a detailed description of'the invention, the respiration apparatus generally comprises delivery means for delivering oxygen or other gas to a persons tracheal passage, exhaust means for discharging gas therefrom to the atmosphere, and operating means for automatically rendering the delivery and discharge means effective alternately. The operating means includes pressure responsive means for controlling the cycling of the device to render the delivery means efiective at one pressure level and to render the exhaust means effective at another pressure level. The apparatus includes delivery control means for controlling the fiow of gas to the persons lungs when the delivery means is effective so that the rate of flow of gas to the persons lungs is in accordance with the persons requirements. The apparatus also includes exhaust control means for controlling the discharge of gas from a person's lungs to the atmosphere when the discharge means is effective so that the exhalation of gas from the persons lungs may be opposed by a predetermined pressure, said discharge control means being operative nevertheless to permit the person to exhale at whatever rate his condition requires, and to permit the pressure in the user's lungs to reach the ambient atmospheric pressure within a predetermined maximum period.

Referring to Fig. 1 of the drawings, the delivery means as there shown comprises a delivery conduit I communicating with a second conduit'2, the upper end 2a of which is adapted to lead to and communicate with any suitable inhalation mask or other means designed to introduce gas to a persons tracheal passage and thence to his lungs. The delivery conduit I communicates with the interior chamber 9 of a valve casing 4 provided with intake port 5 for communication with a source of supply of oxygen or other gas and adapted to admit gas to the delivery. conduit I. The exhaust means for discharging gas from the persons lungs to the atmosphere includes the conduit 2 constituting a discharge conduit communicating with the interior chamber 6 of a valve casing 1 and having an outlet communicating with the atmosphere and comprising the exhaust port 8. v

The discharge of gas by the exhaust means (when the exhaust valve I0 is open) is controlled by exhaust control means including spring loaded valve 50 and orifice or passage 5I regulated by needle valve 53. The details and operation of the exhaust control means will be more fully described later herein.

Thus, the delivery and exhaust means include a common conduit I-2 communicating with the source of supply of oxygen, the user's lungs and the atmosphere.

The operating means for rendering the delivery means and the exhaust means effective alternately includes an intake valve 9 adapted for cooperation with the intake port 5, an exhaust valve I0 adapted for cooperation with the exhaust port 8, and a common actuator comprising a member II interconnecting the intake and exhaust valves '9 and ID for simultaneous operation whereby when the common actuator II is moved in one direction the intake valve 9 is moved to a position opening the intake port 5 for admission of gas to the delivery conduit I and the exhaust valve In is moved to a position closing the exhaust port 8 to prevent discharge of gas from the discharge conduit 2, and thereby prevent discharge of gas from the lungs of the user to the atmosphere. The operating means for efiecting operation of the intake and exhaust valves 9 and I0 includes pressure responsive means responsive to the pressure of gas in the common conduit I-2 of the delivery and exhaust means, and hence responsive to the pressure of gas within the tracheal passage of the user or within the lungs of the user, for controlling the operation of the intake and exhaust valves 9 and In. The pressure responsive means generally designated by the letter A is operative through appropriate electrical means or other suitable means to efiect operation of intake and exhaust valves 9 and I0 whereby when the pressure of gas within the common conduit I-2 reaches a predetermined pressure limit the intake valve 9 is opened and the exhaust valve I0 is closed; and when the pressure of gas within the common conduit I-2 reaches another predetermined limit the intake valve 9 is caused to be closed and the exhaust valve is caused to be opened.

As shown in Figure l, the pressure responsive means A comprises a housing I2 within which is positioned a suitable diaphragm I3 which may be made of thin metal, rubberized fabric or any other suitable material that will withstand the pressures to which it is subjected. This diaphragm I3 defines a pressure chamber I4 within the housing I2, which pressure chamber I4 is in communication through a small orifice I5 and a conduit IS with the common conduit I2. The pressure chamber I4 may be placed in communication with the common conduit I--2 at any desired point therein, but preferably the pressure chamber I4 is placed in communication with the discharge side of common conduit I-2 as shown, and the communication is efiected through the small orifice I5, so that the pressure responsive means is not so greatly afiected by impulse effects of oxygen flow from the intake valve to the user's lungs. The diaphragm I3 carries an actuator comprising a stem I'l associated with the diaphragm I3 for movement therewith, said actuator stem I! having associated therewith a contactor I8 adapted to be moved by the diaphragm I3 into and out of engagement with stationary contacts I9 and 29 for making and breaking successively electric circuits capable of energizing and deenergizing a solenoid 2| for corresponding actuations of the intake and exhaust valves 9 and III. A spring 22 is positioned to act against the diaphragm I3 and is designed to have such flexing characteristics that when low pressures communicated to the pressure chamber I4 are applied to the diaphragm I 3, substantial move ment of the latter will occur, The pressure exerted by the spring 22 upon the diaphragm I3 is adjustable by means of a screw 23 adjustably associated with the housing I2 and bearing against one end of the spring 22. The contacts I9 and 29 are associated respectively with screws 24 and 25 adjustable with respect to the housing I2 for corresponding adjustment of the contacts I9 and 29. By the means 23, 24 and 25, the pressure responsive means A is adjustable to vary the upper and lower pressure limits of gas within the conduit I2, at which limits the diaphragm I3 is effective to move the contactor I8 into engagement with one or the other of the contacts I9 and 20, for corresponding actuation of the intake and exhaust 'valves 9 and III, to render the delivery and exhaust means effective alternately.

Movement of the common actuator II to operate the intake and exhaust valves 9 and I9 in one direction is effected by means of the solenoid 2|, having its core 21 associated with a lever 28 pivoted as at 29 to the apparatus supporting frame 30, said lever 28 being pivoted as at 3| to the common actuator II. Energization of the solenoid 2| serves to move the common actuator I I to the position shown in Fig. 1 wherein the intake valve 9 is open and the exhaust valve I is closed. Movement of the common actuator in an opposite direction to effect closing of the intake valve and opening of the exhaust valve III is effected, upondeenergization of the solenoid 2|, by means of the spring 32, having one end connected to the lever 28 and the other end of said spring connected as at 33 to the apparatus housing 39, the spring 32 acting upon deenergization of the solenoid 2|, to move the lever 28 in a clockwise direction, referring to Fig. 1, about the pivot 29,

Operation of the respiration cycling instrumem talities The operation of the apparatus thus far disclosed may be described as follows:

Assume that the upper end 2a of the common conduit I-2 has been placed in communication with a persons tracheal passage and the intake port placed in communication with a source of supply of oxygen or other gas, the exhaust port 8 gives access to the atmosphere, and that the adjusting means 23, 24 and 25 have been set so that the contactor I8 will make electrical contact with the stationary contact 20 when the pressure of gas within the chamber I4 is at a predetermined minimum level (e. g., at atmospheric pressure or slightly above), and so that the contactor It will make contact with the stationary contact I9 when the pressure in the chamber I 4 reaches a predetermined maximum level. The pressure within th conduit |-2 and the chamber I4 will at the moment of commencement of operation stand at the minimum or approximately atmospheric pressure level. At this minimum pressure level the contactor I 8 will be in engagement with the stationary contact 29 completing an electrical circuit from the negative side of the battery 34 through wire 35, contacts I8 and 29, wires 36 and 31 to the solenoid 2| and thence through wire 38, relay switch 38 and wire 40 to the positive side of the battery 34, thus energizing the solenoid 2|. At this point, therefore, the common actuator II will be in its leftward position, as shown in Figure 1, with intake valve 9 open and exhaust valve I9 closed. This position of actuator II causes the contact 4| carried b the lever 28 to be engaged with the stationary contact 42 completing a holding circuit from the negative side of the battery 34 through wire 43, contacts 42 and 4|, wire 31 to the solenoid 2| and thence through wire 38, switch 39 and wire 40 to the positive side of the battery 34 to maintain the solenoid energized when the contactor I8 moves out of engagement with the contact 20 as the pressure in the chamber I4 rises.

Thus, at the commencement of operation of the apparatus with the pressure of gas in the conduit I2 and chamber I4 at a minimum level, the solenoid 2| is energized to position the common actuator II in its leftward position, as shown in Fig. 1, with the intake valve 9 open to admit the gas from a source of supply to the conduit I and the exhaust valve I0 closed to prevent discharge of gas from the conduit 2 to the atmosphere. With the valve 9 open and the exhaust valve In closed, gas will be delivered from the source of supply to the common conduit I-2 and to the users lungs, causing the pressure in the conduit I--2 and chamber I4 to rise and acting upon the diaphragm I3 to move the contactor I8 out of engagement with the stationary contact 20 and toward a position of engagement with the stationary contact I9. During such movement of the contactor I8, the solenoid 2| will remain energized through the holding circuit above de scribed.

When the pressure of gas within the conduit I-2 rises to a predetermined maximum level, as determined by the adjustment of the means 23, 24, said pressure acting upon the diaphragm I3 will cause movement of th contactor I8 into engagement with the stationary contact I9, thereby completing an electrical circuit from the negative side of the battery 34 through wire 35, contacts I8 and I9, wire 45, relay 46 and wire 49 to the positive side of the battery 34. Completion of this electrical circuit will open the relay switch 39 against the action of the spring 41, thus breaking the electrical circuit through the solenoid 2| and causing the same to be deenergized whereupon the common actuator II will be caused to be moved in a rightward direction, having reference to Fig. 1, by the action of the spring 32 to close the intake valve 9 and open the exhaust valve III, thus rendering the delivery means ineffective and the exhaust means effective, and thereby initiating the exhalation phase of the respiratory cycle of the apparatus during which the user of the apparatus may exhale, if he is breathing spontaneously, or, if he is not breathing spontaneously, the natural elasticity of his lungs will cause exhaust of gas therefrom which is discharged to the atmosphere through the discharge conduit 2 past the spring loaded valve 50 and also through the restricted orifice 5| to the atmosphere through the exhaust port 8.

As the gas is discharged from the conduit 2 to the atmosphere, during the exhalation phase of the respiratory cycle, the pressure within the chamber I4 decreases, causing the contactor I8 to move out of engagement with the stationary contact I9. When the contactor I8 moves out oiv engagement with the stationary contact I9, the electrical circuit through the relay 46 is broken, permitting the relay switch 39 to be again closed by the action of the spring 41 to condition the circuit through the solenoid for subsequent com pletion to again energize the solenoid 2I at such time as the contactor I8 again comes into engagement with the stationary contact 20. The exhalation phase of the respiratory cycle of th apparatus continues until the discharge of gas from conduit 2 to the atmosphere has reduced pressure of gas in the conduit I-2 and the chamber I4 to the predetermined minimum level, determined by the adjustment of the means 23 and 25, to cause movement of the contactor I 8 again into contact with the stationary contact 29. Upon occurrence of the latter event, th solenoid 2| will again be energized as above described, causing movement of the lever 28 in a counterclockwise direction, having reference to Fig. I, about its pivot 29 to move the common actuator I I in a leftward direction, having reference to Fig. l, to

thereby close the exhaust valve I0, preventing further discharge of gas from the system to the atmosphere, and opening the intake valve 9 to again admit gas from the source of supply to the conduit I, thus initiating a new inhalation phase of the respiratory cycle of the apparatus, which will continue until the pressure of gas in the conduit I-2 and the chamber I5 rises to the predetermined maximum level, at which time the apparatus will function as above described to initiate a new exhalation phase of the respiratory ycle.

Description of delivery control means In accordance with the invention, delivery control means, generally designated by the letter B, is prov ded for controlling the delivery of gas to the delivery conduit I and thenc to the users tracheal passage and the users lungs in accordance with his demands or requirements. This control means is adapted to deliver gas to the conduit I at pressures above atmospheric pressure, and said control means is operative responsive to variations in pressure within the delivery conduit to vary the flow of gas thereto in a reciprocal relation to the pressur of gas in said conduit so that flow of gas from the source of sup ply to the delivery conduit I is greatest when the pressure of gas in said conduit I is at a minimum value. and the flow of gas to th conduit I decreases as the pressure therein rises.

Now, describing the delivery control means in detail, the same comprises a housing 69 within which is disposed a pressure responsive diaphragm SI defining a pressure chamber 62 communicating through a port 63 and a conduit 64 with th intake port 5 of the delivery conduit I. The pressure chamber 52 communicates with a source of oxygen or other gas through a port 65 and a conduit 65 leading to said source of supply. The port 65 is controlled by a valve 6'! having a stem 68 pivotally connected to a lever 69 which is pivoted to the casing 60 and also pivoted to an actuating stem I9 fixed to the diaphragm BI. The side of the diaphragm 6| exterior to the chamber 62 is subjected to atmospheric pressure and for this purpose the apertures II are provided in the casing 60. Spring means adjustable relative to the casing 69 is arranged to act upon the diaphragm 5|. To this end a stem I2 is fixed to the diaphragm 6| and said stem I2 has an enlarged head 12a engaged by one end of the spring 13, the

other end of which spring is engaged by anadjusting screw I4 adjustable relative to th casing 60 for varying the pressure exerted by the spring upon the diaphragm BI. A spring I5 acts between the casing 60 and the valve 6'! to urge the the chamber 62. As the pressure of gas inthe chamber 62 rises, the valve 61 gradually closesso as to gradually decrease the rate of flow of gas.

from the source of supply as the pressure ofgas within 1 the chamber 62 rises until at the preselected maximum pressure of gas within the chamber 62, the valve 61 is fully closed to stop the'fio-w of gas from the source of supply. The range of pressures of gas within the chamber 62 at which the delivery control means will cause delivery of gas from the source of supply may be regulated or adjusted by the disposition of the diaphragm BI and the preliminary loading placed thereon by the springs I3 and I5. Conveniently, the adjustment of the pressure range at which the control means is rendered effective to cause delivery of gas from the source of supply is accomplished by regulation of the pressure of the spring I3 on the diaphragm BI by means of the adjusting screw I4. Since the pressure chamber 62 is in communication with'conduit I when the intake valve 9 is open, the flow of gas from the source of supply to the conduit I is variably controlled responsive'to pressure variation in conduit I (and hence in the users lungs) during the inhalation phase of the respiration cycle of the apparatus. Thus, the delivery control means isoperative to vary the rate of flow of gas from the source of supply to the conduit I in a reciprocal relation to the pressure of gas within said conduit I, so that as the-pressure in conduit I rises, the rate of flow decreases, and as said pressure decreases, the rate of flow increases.

For the purposes of the invention it is desirable to supply oxygen to the user of the respiration apparatus at pressures above atmospheric pressure. Where the apparatus is used for the demand supplying of oxygen to flying personnel at high altitudes or fOr the resuscitation of flying personnel at such altitudes, it is desirable to increase the pressure at which gas is supplied to the user as the altitude increases. Moreover, for the purposes of enabling the respiration apparatus of the invention to operate automatically as a resuscitator, it is necessary that the delivery control means for controlling the delivery of gas to the user be capable of response to a range of pressures within the users lungs above atmospheric pressure, in order to automatically supply gas to the users lungs during the inhalation cycle in the event that the user is not breathing spontaneously or his spontaneous respiration rate is insufilcient, so that the apparatus will function automatically as a resuscitator under such conditions.

Description of exhaust control means One of the particular objects of the invention, as above pointed out, is to provide exhaust control means for controlling the discharge of gas from the users lungs during the exhalation phase of the respiratory cycle of the apparatus in such a manner that, whenever it is desirable, the exhalation may be opposed by a redetermined pressure. while at the same time, the user is permitted to exhale at whatever rate he requires, and in such a manner that the pressure of gas in the users lungs is permitted to reach the ambient atmospheric pressure within a predetermined maximum period of the exhalation p ase of the res iratory cycle. To this end the exhaust control means includes means for varying the rate of dischar e of gas from the dischar e conduit 2 as a. function of the pressure of as in said c nduit. The latter means is conseouently effective to vary the rate of discharge of gas from the persons lun s as a function of t e pressure of gas in the nersons lungs or in his tracheal passage. Said latter means is made o erative to vary the rate of discharge of gas as a function of pressu e in the conduit 2 when said pressure is within predetermined limits. The exhaust control means also includes means for effecting discharge of as from the conduit 2 irrespective of said predetermined pres u e limits at which the means for varyin the discharge rate is efiective.

Referring specifically to Fig. 1. the discharge conduit 2 is provided with two separate outlets or channels of flow to the atmosphere which are effective to permit the discharge 01' gas from the conduit 2 when the exhau t valve '0 is open. One 01 these two outlets or channels of fiow from the discharge conduit to the atmos here is provided by the comparatively large port 52 controlled by the spring loaded valve 50. The ot er of said two outlets or channels of dischar e flow of as from the conduit 2 to the atmosphere is provided by the comparativelysmall or restricted orifice or p ssage 5| which is controlled by the needle valve 53.

The sp ing loaded valve 50 includes a valve stem 54 provided with an abutment head 55 against which one end of a spring 56 bears. The other end of said spring bears against a part of a valve adjusting member 51 threadedly ass ciated with the valve casing 'l. Rotation of the valve adiustirg member 51 relative to the valve casing 1 will serve to vary the spring loading on the valve 50 and thus vary the ran e of pressure of gas within the discharge conduit 2, within which the valve 50 will be caused to open to permit discharge of gas from the conduit 2 through the port 52. Once the valve 50 is adjusted, it will be apparent that the same is operative to vary the effective opening of the exhaust port or outlet 52, and hence, to vary the effective discharge capacity of the exhaust means, as the pressure within th conduit |2, tending to open the valve 50 against the ac tion of the spring 56, increases or decreases.

Thus, if the spring loading'on the valve 50 is adiusted so that the valve 50 will open at a predetermined pressure of gas within the discharge conduit 2, it will be apparent that as the pressure of gas within the conduit 2 is increased above said predetermined pressure, the valve 50 will open to a correspondingly greater extent so that the rate of discharge of gas from the conduit 2 through the port 52 is increased as the pressure of gas within conduit 2 increases, and conversely, the rate of discharge flow of gas from the conduit 2 through the port 52 decreases as the pressureof gas within the conduit 2 decreases, until said pressure decreases to the predetermined pressure at which the valve 50 is fully closed by spring 55. It will be apparent also that whenever the exhaust valve I0 is open and the needle valve 53 is adjusted so as to permit the passage of gas through the orifice 5|, gas will continue to be discharged from the conduit 2 to the atmosphere through said orifice 5|, so long as the pressure of gas within the conduit 2 is above the ambient atmospheric pressure, and irrespective of the pressure limits within which the valve 50 is operative.

In accordance with the invention, it is desired to regulate the discharge control means including the spring loaded valve 50 and the restricted orifice 5! in such a manner that said control means provides a predetermined pressure opposing the discharge of gas to the atmosphere during the exhalation phase of the respiratory cycle of the apparatus when the exhaust port 8 is open, while at the same time permitting the user of the apparatus to exhale at whatever rate he requires within the limits of operation'of the spring-loaded valve 50. It is also desired to regulate the discharge control means in such a manner that the pressure of gas Within the conduit 2 will reach the ambient atmospheric pressure within a desired maximum exhalation period. The maximum length of the exhalation period is regulated by adjustment of the spring loading on the valve 50 and also by adjustment of the needle valve 53, bearing in mind that the pressure drop in the common conduit l-2 to the predetermined level, as determined by the adjustment of the pressure responsive means A, is efiective to operate the intake and exhaust valves 9 and ill to close the exhaust valv [0 and open the intake valve 9 to begin a new inhalation phase of the respiratory cycle. Hence, the maximum length of the exhalation period during which the intake valve 9 is closed and the exhaust valve I0 is open to permit discharge of gas from the users lungs to the atmosphere may be determined by adjustment of the discharge control means including the spring loaded valve 50 and the needle valve 53.

General operati n of the respiration apparatus As an example of the manner of operation of the respiration apparatus of the invention as a whole, including the delivery control means B and the exhaust control means comprising spring loaded valve 50 and the adjustable orifice 5|, the following description of such general operation will now be given. Assuming that the apparatus is to be used at altitudes just above thirty-five thousand feet, it is desired to adjust the delivery control means so that gas will be delivered to the lungs of the user at a pressure equal to eight inches of water and to adjust the exhaust control means so as to oppose exhalation or discharge of gas from the lungs of the user with an opposing pressure equal to four inches of water. The pressure limits just mentioned have been found to be suitable for proper respiration at altitudes Just above thirty-five thousand feet. As the altitude increases above thirty-five thousand feet it is desirable to increase both the pressure at which gas is delivered to the lungs of the user and the pressure opposing exhalation therefrom gradually until at an altitude of approximately fifty thousand feet the apparatus would be adjusted so as to deliver gas to the users lungs at a pressure approximately equal to twelve inches of water and so as to provide a pressure opposing exhalation equal to approximately eight inches of water. The maximum and minimum pressure limits within which the respiration apparatus will operate are of course primarily controlled by adjustment of a pressure responsive means A. That is to say, the maximum pressure limit of the apparatus, or the pressure of gas'within the conduit [-2 which will cause operation of the intake and exhaust valves 9 and I!) to initiate the exhalation phase of the respiratory cycle of the apparatus, is determined by adjustment of the pressure responsive means .A. Likewise, the minimum pressure limit of the apparatus, or the pressure of gas within the conduit l--2, at which the intake and exhaust valves 9 and ID will operate to initiate a new inhalation phase of the respiratory cycle of the apparatus, is also determined by the adjustment of the pressure responsive means.-

For the purposes of the use of the apparatus at altitudes just above thirty-five thousand feet, the pressure responsive means A may be adjusted for a maximum pressure equal to eight inches of water.- To this end, the means 23 and 24 will be adjusted so that the oontactor M will just engage the stationary contact l9 when thepressure of gas within the conduit l2 is equal to a pressur of eight inches of water. Preferably, the minimum pressure limit of the apparatus will be adjusted so as to be slightly above the ambient atmospheric pressure. To this end, the means 23, 25 will be adjusted so that the contacto-r 13 will just make contact with the stationary contact 20 when the pressure of gas within the conduit |2 reaches a pressure equal to 4 inch of water. Now the delivery control means B is preferably adjusted so as to deliver gas to the lungs of the user at a pressure slightly higher than the maximum pressure setting of the pressure responsive means A. To this end, the adjusting screw 14 of the delivery control means B will be adjusted so that the valve 61 will o en whenever the pressure of gas within the chamber 62 falls below said high pressure sett ng of the control means B. say eight and one-half inches, say a pressure equal to eight and one-half inches of water. Now, for the particular condition of use of the ap aratus with which we are dealingnamely, altitudes just above thirty-five thousand feetthe exhaust control means will be set so as to provide a constant pressure equal to a pressure of four inches of water opposing exhalation of gas from the users lungs. To this end, the valve-adjust ng means 51 and. the needle valve 53 will be adjusted so that the valve 50 will just open when the pressure of gas within the conduit 2 equals a pressure of four inches of water durin the exhalation phase of the respiratory cycle when the exhaust valve IQ is open. It will be understood that after the primary adjustment of a means 53, has been made as just described. the needl valve 53 may be further regulated, if desired, by the user so as to permit comfortable exhalation. However, the primary adjustment will be generally satisfactory for all practical purposes. The adjustment of the various instrumentalities as just described, is merely given for the purpose of illustration of desirable adjustments for a particular condition. It will be understood that the adjustments may be varied to suit particular different conditions. Means may be provided, if desired, to automatically control the primary adjustments of the pressure responsive means A, delivery control means B and the exhaust control means as a function of altitude so that as the altitude increases, the upper pressure limit adjustments of these instrumentalities may be automatically increased.

Now, with the apparatus adjusted as above specifically described, the operation will be substantially as Iollowsz' Upon the commencement of an inhalation phase of the respiratory cycle, during which the exhaust valve I0 is closed and the intake valve 9 is open, the gas will be delivered to the lungs of the user at a pressure slightly above the maximum pressure setting of the pressure responsive means A and the gas will flow to the users lungs at a rate determined by the rapidity of the users spontaneous inspiration, the rate of flow gradually decreasing as the pressure within the conduit l-2 rises until the pressure within the conduit l-Z reaches the predetermined maximum setting of'the pressure responsive means A, at which time the intake valve 9 will be closed toshut off the supply of gas to the users lungs and the exhaust valve ID will he opened to initiate the exhalation phase of the respiratory cycle. Upon the happening of the latter event, the gas will be discharged from the users lungs at whatever rate he requires until the pressure within the conduit |2 is reduced to a pressure equal to four inches of water, at which time the spring loaded valve 5|! will close and gas will continue to be discharged to the atmosphere through the restricted orifice I at a substantially constant rate of discharge flow until the pressure of gas within the conduit l-2 reaches the predetermined minimum level, determined by. the adjustment of the pressure responsive means A, whereupon the exhaust valve I0 will close and the intake valve 9 will again open to initiate a new inhalation phase of the respiratory cycle.

If, at any time during the inhalation phase of the respiratory cycle, the users demand for oxygen increases by a greater, or more rapid, expansion of the users lungs, the pressur within the conduit l2 will, as a result, be correspondingly decreased so that the valve 61 of the delivery control means will be caused to open to a greater extent to provide an increased rate of .delivery of gas to the users lungs to satisfy such increased demand.

It will be understood that the respiratory cycle of the apparatus is controlled by the users own spontaneous respiration when his spontaneous breathing rate exceeds the minimum rate (for which the apparatus is adjusted) sufilcient to maintain useful consciousness. Such minimum rate may, for instance, be eight respirations per minute.

When, however, the users spontaneous respiration rate decreases below the minimum rate of eight respirations per minute, or when the user ceases breathing entirely, the apparatus will automatically continue to deliver oxygen to the users lungs and discharge gas therefrom at the rate of eight respirations per minute. This minimum rate may be adjusted in the manner later herein described.

Now, referring to Figure 2, the operation of the apparatus is graphically illustrated by the pressure-flow diagram of said figure. In Fig. 1, both pressure and rate of flow are plotted against time, the curve representing flow during inspiration and the curve 8] representing pressure during inspiration. The curve 82 represents pressure during expiration. At the commencement of the inhalation phase of the respiratory cycle of the apparatus of the invention, at the moment when the exhalation valve I0 is moved to closed position and the intake valve -9 is moved to open position, the pressure of gas in a conduit I--2 is at its minimum (value, as determined by the minimum setting of the pressure responsive means A. For the purposes of this description, said minimum pressure level is represented by the zero line 83.

From Fig. 2 it will be seen that at the commencement of the inhalation phase of the respiratory cycle, the pressure of gas within the conduit |-2 represented by the curve 8| is at minimum value and the flow of oxygen into conduit I2, represented by the curve 80, is greatest at such time. Thus, if the users demand for oxygen is constant as when he is breathing spontaneously at a constant rate, or if the users spontaneous breathing has ceased or his rate of respiration is insuflicient to maintain useful consciousness, the pressure within the conduit l-2 rises in accordance with the pressure curve 8, as the inhalation phase of the respiratory cycle progresses, and the flow of oxygen decreases in accordance with the curve 80 as the pressure within the conduit [-2 rises until at the maximum pressure of gas within the conduit l 2, represented at the point 84 (which is determined by the maximum pressure setting of the pressure responsive means A), the flow is at a minimum value, as represented at the point 85 on curve 80. The time period of the inhalation phase of the respiratory cycle is represented at 86 along the base line 83. The reciprocal relation between the pressure of gas in the conduit l-2, and the flow of gas thereto during the inhalation phase of the respiratory cycle, which results from the operation of the delivery control means B, is thereby graphically illustrated. Obviously, if the users demand for oxygen increases, during inspiration, this will be reflected by a greater or more rapid expansion of the user's lungs, resulting in corresponding variations in pressure and flow and in the time period of inspiration.

The functioning of the exhaust control means during the exhalation phase of the respiratory cycle of the apparatus is also graphically illustrated in Fig. 2. During the exhalation phase of the respiratory cycle the pressure of gas within the conduit l--2 decreases, in accordance With the curve 82, to the pressure level represented by the point 81 within a time period E-l. The pressure level at the point 81, corresponding with the pressure at which the spring loaded valve 50 closes, is determined by the adjustment of the spring loading thereon. The expiration period E-J represents a normal expiration period of a spontaneously breathing person. At the end of such normal expiration period E-l the normally breathing person inhales spontaneously, causing a sharp drop in the pressure of gas within the conduit 1-2, as represented by thesteep decline R3 in the pressure curve, so that immediately pon the commencement of spontaneous inhalation, the pressure of gas in the conduit |-2 drops to the predetermined minimum value at a point 88 (Fig. 2) within a very short period of time, or substantially concurrent with the commencement of inhalation. The predetermined minimum value of pressure within the conduit l2 occurring at the point 89 is that determined by the minimum pressure settingv of the pressure responsive means A, at which time the pressure responsive means A is operative to close the exalation valve and open the intake valve 9 to commence a new inhalation phase of the respiratory cycle of the apparatus. When inhalation occurs. dropping the pressure in conduit I- 2 to the minimum value as at 89. a new inhalation cycle of the apparatus commences in which the pressure-flow pattern of inspiration period 88 is repeated, as indicated by solid lines and 8|. It will thus be seen that when the user of the apparatus is breathing spontaneously at a respiration rate more rapid than the minimum respiration rate for which the apparatus is set, his expiration period will extend until such time as his spontaneous inhalation commences, whereupon the apparatus is immediately conditioned, as a result of the users spontaneous inhalation, for the commencement of a new inhalation phase or the respiratory cycle of the apparatus.

Should the user's spontaneous breathing cease, or in the event that his spontaneous respiration rate does not exceed the predetermined minimum rate, the exhalation phase of the respiratory cycle of the apparatus will extend for a period 13-2, at the end of which period the apparatus is autophase of the respiratory cycle commences irrespective of the breathing or nonbreathing of the user. (The maximum length of the expiration period E-2 is controlled by adjustment of the exhaust control instrumentalities 53, 51.) Under such conditions, (as when the apparatus is functioning as a resuscitator), the inhalation phase of the respiratory cycle of the apparatus of the invention takes place in accordance with the diagrammatic illustration of Fig. 2 and occupies the ins iration period 86, the pressure of gas within the conduit l2 rising, in accordance with curve to the maximum point 84 and the rate of flow decreasing, in accordance with curve 80, as the pressure rises, so that when the pressure of gas within the conduit i-2 reaches the predetermined maximum point, the apparatus is conditioned for the exhalation phase of the respiratory cycle by the closing of the intake valve 9 and the opening of the exhaust valve Hi. The exhalation phase of the respiratory cycle then takes place automatically, the natural resilience of the persons lungs tending to collapse the same. The gas is discharged from the conduit.2 through the port 52 andthe small orifice 5| until the pressure of gas within the conduit l2 decreases to the predetermined. level represented at the point 81 (Fig. 2) at which the spring loaded valve 50 closes --arking the end of a period corresponding to the exhalation period E-I. Henceforth, during resuscitation, gas is discharged from the conduit 2 solely through the restricted orifice 5| during a period E3. During this period E--3 the pressure of gas within the conduit l2 declines in accordance with the dotted line curve 82 until the pressure of gas within the conduit l2 reaches the predetermined minimum level (as determined by the minimum pressure setting of the pressure res onsive means A) at a point 8| marking the end of the exhalation period 15-8, at the end of which period the operation of the pressure responsive means A causes closing of the exhaust valve l0 and opening of the intake valve 9 to automatically commence a new inhalation phase of the respiratory cycle of the apparatus during which gas flows to the conduit l-I. in accordance with dotted line pressure and flow curves Ma and 80a, in the manner above described. The curves 80a and Ma indicate a repetition of the pressure-flow pattern of inspiration period 88.

From the foregoing description. it will be apparent that the exhalation period E2 represents the maximum exhalation period for which the apparatus is adjusted at any particular time.

The length of the exhalation period E2 may be regulated by the adjustment of the springloading of the valve 50 and the adjustment of the needle valve 53. It will be apparent also that, once the apparatus is adjusted, at the end of such maximum exhalation period :E- 2 it automatically functions to commence a new inhalation cycle of the apparatus in which oxygen is delivered to the users lungs whether or not he is breathing spontaneously. The exhalation phase of the apparatus extends for the full length of the maximum exhalation period E-c-3, of course, only in the event that the user does not spontaneously inhalepriorto the end of said period Isl- 2. Adjustment of means -50, 53 consequently controls the minimum respiration rate of the apparatus.

If the user is breathing spontaneously at a rate sufficient to maintain useful consciousness, the delivery of gas to his lungs is regulated by his demand, the rate of flow of gas varying as a reciprocal of the pressure value within the conduit |--2. If the user ceases breathing entirely, or his respiration rate becomes insufficient to maintain useful consciousness, the apparatus nevertheless functions to initiate alternate inhalation and exhalation phases of an automatic respiration cycle .so as to deliver gas to the users lungs and discharge the same therefrom; and under such condition the flow of gas to the users lungs varies as a reciprocal of the pressure within the conduit 'i 2, and discharge of gas from the users lungs occurs in accordance with the curvessz, 92.

It will also be apparent that the operation of the discharge control means is such that the user may exhale at whatever rate his condition requires when he is breathing spontaneously, the spring loaded valve 5% being operative to permit varying rates of discharge of .gas from the conduit i-.2;; and'that, also, the exhalation period E-l will extend so long as the user is exhaling, whenever his respiration rate is sufficient to maintain useful consciousness, and he may begin a new inhalation phase at any time during the exhalation period E2 so that the length of the exhalation period E-l is determined by, and the time within the period E-2 at which a new inhalation phase of the apparatus commences will correspond with, the time at which the user ceases exhalation and begins spontaneous inhalation. Thus, the exhaust control means of the invention makes it possible to provide a preselected positive pressure opposing exhalation while permitting the user to exhale at Whatever rate his condition requires, when his spontaneous respiration rate is sufficient to maintain useful consciousness, and at the same time, the orifice 5| is continuously open during the exhalation phase of the apparatus to permit the pressure within the system to reach substantially atmospheric pressure, or the minimum pressure limit of operation of the system, within a predetermined maximum period of time E2, to then automatically initiate a new inhalation phase of the respiratory cycle of the apparatus, in the event spontaneous respiration has ceased, or the users spontaneous respiration rate is insufficient to maintain useful consciousness. Under the latter conditions, the apparatus functions to effect alternate delivery and discharge of oxygen to and from the users lungs at a predetermined minimum respiration rate determined by adjustment of the apparatus. Adjustment of delivery control instrumentalities El, 13, I5 controls the maximum inspiration period 86 effective when the users spontaneous respiration rate does not exceed the predetermined minimum .respiration rate. The size of the restricted orifice 5i and the adjustment of the needle valve 53 control the length of time that the expiration period E--2 continues after the spring loaded valve :59 closes. Hence, adjustment of these latter discharge control instrumentalities controls the maximum expiration period E-2, likewise efiective when the users spontaneous respiration does not exceed the predetermined minimum respiration rate.

It will :be apparent that various types of adjustment .of the pressure responsive means A, thedelivery control means B, and the discharge control manstfd, v5'5 may be made to suit various conditions, and that these adjustments may be availed of by a skilledoperator or physician in a particularly advantageous .manner to improve anesthesia techniques and to improve the-treatment of various respirator conditions requiring close control of the Various phases of the artificial respirator cycle.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent is:

1. In respiration apparatus of the class described, a conduit adapted for communication with gas administeringmeansanintake port for admitting gas to said conduit, an exhaust port communicating with said conduit and with the atmosphere, intake and exhaust valves for said intake .andexhaust ports, operating means for opening and closing said valves, said operating. means being operative to close the respective valves alternately and to open said valves alternately, said operating means including pressure responsive means responsive to the pressure of gas in said conduit for opening one of said .valves and closing the other valve when thepressure insaidconduit reaches a predetermined limit and for reversing the operations of said valves when the pressure within said conduit reaches another predetermined limit, said conduit having an outlet to the atmosphere when the exhaust valve is open, valve means including a valve for varying the rate of flow of gas through said outlet, yieldable means normally urging said last valve to a position closing said outlet, said yieldable means being arranged to act upon said last valve in opposition to the pressure of gas in said conduit acting upon said last valve and means for adjusting said yieldable means to vary the pressure range within which the pressure of gas in said conduit may effect opening of said latter valve, and a passage by-passing said last valve.

2. Respiration apparatus as claimed in claim 1, and valve means for controlling the flow of gas through said by-passage.

3. In respiration apparatus of the class described, a conduit adapted for communication with gas administering means, an intake port for admitting gas to said conduit, an exhaust port communicating with said conduit and with the atmosphere, intake and exhaust valves for said intake and exhaust ports, operating means for opening one of said valves and closing the other of said valves, and for reversing the operation of said valves, said conduit having two independent flow channels communicating with said exhaust port. valve means including a valve for controlling gas flow through the first channel, said last valve being arranged to open under pressure of gas in said conduit, and yieldable means normally urging said last valve to a position closing said first charmel, said yieldable means being arranged to act on said last valve in opposition to the pressure of gas in said conduit acting upon said last valve.

4. Respiration apparatus as claimed in claim 3 and valve means for controlling the flow of gas through the second channel.

5. Respiration apparatus as claimed in claim 3 wherein the effective cross-sectional area of the second channel is smaller than the effective crosssectional area of the first channel.

6. Respiration apparatus as claimed in claim 3, wherein the effective cross-sectional area of the second channel is smaller than the efiective crosssectional area of the first channel, and manually operable valve means for controlling the flow of ga through the second channel.

7. In apparatus of the class described in combination, a conduit adapted for communication with gas administering means, said conduit having two separate discharge channels for discharging gas from said conduit to the atmosphere, valve means including a valve for controlling gas flow through the first of said channels, said valve means including a valve arranged to open under pressure of gas in said conduit, and yieldable means normally urging said valve to a position closing said first channel, said yieldable means being arranged to act upon said valve in opposition to the pressure of gas in said conduit acting upon said valve, exhaust valve means operative independently of the aforesaid valve means for controlling discharge of gas through said channels to the atmosphere, intake valve means for controlling admission of gas to said conduit, and operating means for said intake and exhaust valve means and operative to move one of said intake and exhaust valve means to open position while moving the other of said intake and exhaust valve means to closed position, and said operating means being operative to reverse the operation of said intake and exhaust valve means.

8. In apparatus of the class described in combination, a conduit adapted for communication with gas administering means, said conduit having two separate discharge channels for discharging gas from said conduit to the atmosphere, valve means including a valve for controlling gas flow through the first of said channels, said valve means including a valve arranged to open under pressure of gas in said conduit, and yieldable means normally urgin said valve to a position closing said first channel, said yieldable means being arranged to act upon said valve in opposition to the pressure of gas in said conduit acting upon said valve, exhaust valve means operative independently of the aforesaid valve means for controlling discharge of gas through said channels to the atmosphere, intake valve means for controlling admission of gas to said conduit, and operating means for said intake and exhaust valve means, said operating means including pressure responsive means responsive to the pressure of gas in said conduit for moving one of said intake and exhaust valve means to open position while moving the other of said intake and exhaust valve means to closed position, said pressure responsive means being responsive to the pressure of gas in said conduit for reversing the operation of said intake and exhaust valve means.

9. Respiration apparatus as claimed in claim 8 wherein the effective cross-sectional area of the second channel is relatively small as compared to the efiective cross-sectional area of the first channel.

10. Respiration apparatus as claimed in claim 8 wherein the effective cross-sectional area of the second channel is relatively small as compared to the effective cross-sectional area of the first channel, and valve means for varying the effective cross-sectional area of said second channel.

ALVIN M. CAHAN.

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US2583502 *May 23, 1946Jan 22, 1952Leonard A WigginsBail out demand regulator
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US7762252 *Nov 8, 2006Jul 27, 2010Mine Safety Appliances CompanyDevices, systems and methods for operation of breathing apparatuses in multiple modes
US8256420 *Jun 4, 2010Sep 4, 2012Mine Safety Appliances Co.Devices, systems and methods for operation of breathing apparatuses in multiple modes
US20070251525 *Nov 8, 2006Nov 1, 2007Prete Christopher LDevices, systems and methods for operation of breathing apparatuses in multiple modes
US20100236554 *Jun 4, 2010Sep 23, 2010Prete Christopher LDevices, systems and methods for operation of breathing apparatuses in multiple modes
Classifications
U.S. Classification137/102, 137/487.5, 137/494, 251/129.2, 137/624.14
International ClassificationA61M16/00
Cooperative ClassificationA61M16/00
European ClassificationA61M16/00