VENTILATOR

• US 3,756,229 A
• Filed: 12/14/1970
• Issued: 09/04/1973
• Est. Priority Date: 12/14/1970
• Status: Expired due to Term

• Current Assignee: Louis A. Ollivier
• Original Assignee: Louis A. Ollivier
• Inventors: Ollivier, Louis A.
• Primary Examiner(s): Gaudet, Richard A.
• Assistant Examiner(s): Dunne, G. F.
• Application Number:
  US05/097,933
• Time in Patent Office: 995 Days
• Field of Search: 128/145.5,145.6,145.7,145.8 137/63R
• US Class Current: 128/204.26
• CPC Class Codes: A61M 16/00 Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes stimulating the respiratory movement by mechanical, pneumatic or electrical means, iron lungs combined with gas breathing means A61H31/00
• CPC Class Codes: Y10S 137/908 Respirator control

Abstract

A fully pneumatic ventilator capable of both pressure-cycled and volume-cycled operation. A flow controller operates on the basis of a difference between two control pressures, the lesser of which gradually increases during each inspiratory phase of a breathing cycle, to give a flow which starts out at a relatively high rate and is gradually reduced until cut off. In volumecycled operation, the ventilator employs a cycle generator and a time-volume valve to generate an inspiratory time, a ratio between the expiratory time and the inspiratory time, and to set a volume to be delivered. The time-volume valve enables independent setting of the volume and the inspiratory time. The cycle generator and the time-volume valve supply the flow controller with its control signals, and in turn supplies the patient with the breathing gas. There is a relief valve to avoid exerting too much pressure on the patient'"'"''"'"'s airways, and there is a vacuum relief preventing too great a suction upon them. An override ends an expiratory phase and starts a new inspiratory phase if the patient seeks to initiate inspiration. In the pressure-controlled mode of operation an airway pressure sensor and controller is employed, and the cycle generator and the time portion of the time-volume valve are not used. Various safety features are provided in both modes.

Claims

1. A volume-cycled fully pneumatically operated pneumatic ventilator for connection to a supply of breathing gas, including in combination:

pneumatically operated flow control means for providing breathing gas during the inspiratory phase of each breathing cycle at a rate dependent upon the difference between first and second control pneumatic pressures, PC1 and PC2, pneumatically operated ratio control means for generating said pressure PC1 at a constant value and only during the inspiratory phase, for delivering said pressure PC1 to said flow control means, and for determining the ratio of inspiratory time to expiratory time for each said cycle, pneumatically operated time control means connected to said ratio control means for determining an inspiratory time for each breathing cycle, independently of the volume to be delivered, and for generating said second control pneumatic pressure PC2 from said pressure PC1 at a value always less than said pressure PC1 when the pressure PC1 is present, and sending said pressure PC2 to said flow control means, said time control means increasing second control pressure PC2 during the inspiratory phase from a minimum value to a maximum value, then decreasing it during the expiratory phase from said maximum value to said minimum value, and pneumatically operated volume control means connected to said time control means and to said flow control means for determining, independently of time, the volume of breathing gas delivered in each inspiratory phase.

2. The ventilator of claim 1 having a patient airway conduit connected to said flow control means for providing said breathing gas to a patient, an exhalation valve in said patient airway conduit, and control means for actuating said exhalation valve in synchronization with said time control means, for opening said exhalation valve during each said expiratory phase and closing it during each said inspiratory phase.

3. The ventilator of claim 1 wherein said time control means is connected to said ratio control means for receiving said pressure PC1 by a parallel network of a check valve and a restriction, means for opening said check valve during each inspiratory phase for rapid flow of gas at said PC1 pressure and for closing it during each expiratory phase, so that said PC2 pressure flows back only through said restriction, said restriction being sized to be effective at the shorter values of the time setting, said ventilator also having means comprising a part of said ratio control means for bleeding said pressure PC1 to atmosphere at the beginning of each expiratory phase.

4. The ventilator of claim 1 having a manually actuated sigh valve connected to said time control means by a conduit into which said PC2 pressure is delivered, and a sigh chamber to which gas from said conduit is admitted when said manually actuated sigh valve is opened, thereby increasing the capacity of the timing system and lengthening both the inspiratory and expiratory phases proportionately, with proportional increase in volume, while said manually actuated valve is held open.

5. The ventilator of claim 1 having pneumatically operated override means for actuation by a patient able to initiate a new inspiratory phase before completion of a controlled expiratory phase, comprising a patient airway conduit connected to said flow control means, means connected to said patient airway conduit for sensing a patient-induced vacuum of given value, signal supply means for producing a pressure signal when said given value is sensed, and means for venting said PC2 pressure from its then pressure to its minimum pressure upon application of said signal thereto.

6. A volume-cycled fully pneumatically operated pneumatic ventilator, including in combination:

supply means for supplying a breathing gas at a first regulated pressure P1, pneumatically operated regulator means connected to said supply means and having an outlet for said gas at a second, lower, pressure P2, pneumatically operated flow control means connected to said supply means for providing breathing gas at a rate dependent upon the difference between first and second control pneumatic pressures, PC1 and PC2, a patient airway conduit connected to said flow control means for flow therethrough of said breathing gas, said conduit having an exhalation valve, pneumatically operated ratio control means connected to said regulator means for generating from said pressure P2, the pressure PC1 at a constant value, for delivering said pressure PC1 to said flow control means, and for determining the ratio of inspiratory time to expiratory time for each said cycle, pneumatically operated time control means connected to said ratio control means for determining an inspiratory time for each breathing cycle, independently of the volume to be delivered, and for generating said second control pneumatic pressure PC2 from said pressure PC1 and sending it to said flow control means, means in said ratio control means for causing said first control pressure PC1 to be present only during the inspiratory phase and to be constant during that phase, said second control pressure PC2 being always less than PC1 during the inspiratory phase and increasing continually during that phase from a minimum value to a maximum value, means in said ratio control means for decreasing continually said pressure PC2 during the expiratory phase from said maximum value to said minimum value, pneumatically operated volume control means connected to said time control means and to said supply means at pressure P1 and to said flow control means at a pressure P3 for determining, independently of time, the volume of breathing gas to be delivered in each inspiratory phase, and pneumatically operated exhalation valve control means connected to said time control means and said exhalation valve for synchronizing the opening of the exhalation valve with said expiratory phase and the closing thereof with said inspiratory phase.

7. A volume-cycled pneumatic ventIlator, including in combination:

supply means for supplying a breathing gas at a first regulated pressure P1, regulator means connected to said supply means and having an outlet for said gas at a second, lower, pressure P2, flow control means connected to said supply means for providing breathing gas at a rate dependent upon the difference between first and second control pneumatic pressures, PC1 and PC2, a patient airway conduit connected to said flow control means for flow therethrough of said breathing gas, said conduit having an exhalation valve, ratio control means connected to said regulator means for generating from said pressure P2, the pressure PC1 at a constant value, for delivering said pressure PC1 to said flow control means, and for determining the ratio of inspiratory time to expiratory time for each said cycle, time control means connected to said ratio control means for determining an inspiratory time for each breathing cycle, independently of the volme to be delivered, and for generating said second control pneumatic pressure PC2 from said pressure PC1 and sending it to said flow control means, means in said ratio control means for causing said first control pressure PC1 to be present only during the inspiratory phase and to be constant during that phase, said second control pressure PC2 being always less than PC1 during the inspiratory phase and increasing continually during that phase from a minimum value to a maximum value, means in said ratio control means for decreasing continually said pressure PC2 during the expiratoy phase from said maximum value to said minimum value, volume control means connected to said time control means and to said supply means at pressure P1 and to said flow control means at a pressure P3 for determining, independently of time, the volume of breathing gas to be delivered in each inspiratory phase, and exhalation valve control means connected to said time control means and said exhalation valve for synchronizing the opening of the exhalation valve with said expiratory phase and the closing thereof with said inspiratory phase, said flow control means comprising a diaphragm assembly of three diaphragms, namely, first and second outer diaphragms of equal effective area and a central diaphragm of smaller effective area, a seat at one end of said diaphragm assembly, a first chamber at one end of said diaphragm assembly closed by said first outer diaphragm and having an outlet orifice toward and away from which said seat moves, flow through said outlet orifice being varied according to the position of said seat, said first chamber having an inlet connected to said volume control means at said pressure P3, a second chamber between said first outer diaphragm and said central diaphragm connected to said time control means at pressure PC2, a third chamber between said central diaphragm and said second outer diaphragm connected to said ratio control means at pressure PC1, and a fourth chamber at the opposite end of said diaphragm assembly from said first chamber and connected to said supply pressure P1, compression spring means in said fourth chamber bearing on said diaphragm assembly, and means for setting the degree of compression of said compression spring means, whereby as said pressure PC2 increases during the inspiratory phase and said pressure P1 remains constant, the outflow from said orifice decreases during said inspiratory phase from a maximum to a minimum, and whereby the outflow is shut off during said expiratory phase, as said pressure PC1 is then atmospheric and PC2 is greater than PC1.

8. The ventilator of claim 6 having pneumatically operated override means for actuation by a patient able to initiate a new inspiratory phase before completion of a controlled expiratory phase, comprising pneumatically operated means connected to said patient airway conduit for sensing A patient-induced vacuum of given value, pneumatically operated signal supply means for producing a pressure signal when said given value is sensed, and pneumatically operated means for venting said PC2 pressure from its then pressure to its minimum pressure upon application of said signal thereto.

9. A volume-cycled pneumatic ventilator including in combination:

supply means for supplying a breathing gas at a first regulated pressure P1, regulator means connected to said supply means and having an outlet for said gas at a second, lower, pressure P2, flow control means connected to said supply means for providing breathing gas at a rate dependent upon the difference between first and second control pneumatic pressures, PC1 and PC2, a patient airway conduit connected to said flow control means for flow therethrough of said breathing gas, said conduit having an exhalation valve, ratio control means connected to said regulator means for generating from said pressure P2, the pressure PC1 at a constant value, for delivering said pressure PC1 to said flow control means, and for determining the ratio of inspiratory time to expiratory time for each said cycle, time control means connected to said ratio control means for determining an inspiratory time for each breathing cycle, independently of the volume to be delivered, and for generating said second control pneumatic pressure PC2 from said pressure PC1 and sending it to said flow control means, means in said ratio control means for causing said first control pressure PC1 to be present only during the inspiratory phase and to be constant during that phase, said second control pressure PC2 being always less than PC1 during the inspiratory phase and increasing continually during that phase from a minimum value to a maximum value, means in said ratio control means for decreasing continually said pressure PC2 during the expiratory phase from said maximum value to said minimum value, volume control means connected to said time control means and to said supply means at pressure P1 and to said flow control means at a pressure P3 for determining, independently of time, the volume of breathing gas to be delivered in each inspiratory phase, exhalation valve control means connected to said time control means and said exhalation valve for synchronizing the opening of the exhalation valve with said expiratory phase and the closing thereof with said inspiratory phase, override means for actuation by a patient able to initiate a new inspiratory phase before completion of a controlled expiratory phase, comprising means connected to said patient airway conduit for sensing a patient-induced vacuum of given value, signal supply means for producing a pressure signal when said given value is sensed, and means for venting said PC2 pressure from its then pressure to its minimum pressure upon application of said signal thereto, said means for sensing comprising a first diaphragm assembly in a housing and having a first large-area diaphragm and a second small-area diaphragm, with a first chamber between them connected to said airway conduit, the other side of said first large-area diaphragm being vented to the atmosphere, the other side of said second small-area diaphragm being open to a second chamber vented to the atmosphere, and a seat supported by said first diaphragm assembly, spring means in said first chamber, and sensitivity control means for setting the pressure exerted by said spring means against said first diaphragm assembly, and a detector assembly having a second diaphragm assembly open at one end to said second chamber and having a tubular extension that provides an axial conduit and is opened and closed by said seat, spring means acting on said second diaphragm assembly to urge it to open said axial conduit, and a third chamber on the opposite end of said second diaphragm asembly, means for limiting tHe motion of said second diaphragm assembly to a fixed amount, and passage means through said second diaphragm assembly into said third chamber from said axial conduit, said third chamber having an inlet with a restricted orifice leading into said third chamber and connected to said regulator at the pressure P2, and a port connecting said third chamber to said signal supply means.

10. The ventilator of claim 9 having a relay for said detector assembly comprising a third diaphragm assembly having a pair of diaphragms of equal effective areas defining a fourth chamber on one side of said third diaphragm assembly, connected to the third chamber for maintaining the same pressure as in said third chamber, a fifth chamber between said diaphragms and vented to atmosphere, and a sixth chamber on the other side of said third diaphragm assembly, said third diaphragm assembly having an axial opening and a passageway opening from said sixth chamber into said fifth chamber, a seventh chamber joined to said sixth chamber by a port, a poppet for opening and closing said port and having an extension for engaging said axial opening and closing it when engaged by said third diaphragm assembly, said third diaphragm assembly operating when in contact with said poppet to open said port, said seventh chamber having an inlet connected to said P2 pressure, and a signal conduit connecting said sixth chamber to said means for venting said PC2 pressure.

11. The ventilator of claim 6 having a manually adjustable pneumatically operated pressure relief valve connected to said patient airway conduit for venting pressure to atmosphere when it exceeds a preset value.

12. The ventilator of claim 6 having a vacuum release valve connected to said patient airway conduit for admitting air to said airway conduit if the vacuum therein exceeds a predetermined value.

13. The ventilator of claim 6 having a manually actuated sigh valve connected to said pressure PC2 and a sigh chamber to which gas at pressure PC2 is admitted when said manually actuated valve is opened, thereby increasing the capacity of the timing system and lengthening both the inspiratory and expiratory phases proportionately, with proportional increase in volume, while said manually actuated valve is held open.

14. The ventilator of claim 6 having a control conduit connecting said exhalation valve to said patient airway conduit through a restriction and connecting exhalation valve to said exhalation valve control means and wherein said exhalation valve control means is connected to said pressure PC1 and comprises a diaphragm valve biased by a spring for venting said control conduit to atmosphere during said expiratory phase, said diaphragm valve being closed by said pressure PC1 overcoming said bias spring when said pressure PC1 is present during said inspiratory phase.

15. The ventilator of claim 6 having pneumatically operated means for operating humidifying, nebulizing, and high-pressure exhalation means through an operating conduit, comprising pneumatic relay means connected to said pressure PC1 and to said pressure P3 for generating a pressure equal to PC1 and for conducting it to said operating conduit during said inspiratory phase and for bleeding said operating conduit to atmosphere during said expiratory phase.

16. A fully pneumatic volume-cycled ventilator, providing inspiratory phases alternating with expiratory phases, including in combination:

supply means for supplying a breathing gas at a first regulated pressure P1, regulator means connected to said supply means and having an outlet for said gas at a second, lower, pressure P2, pressure generating means connected to said regulator means for generating from said pressure P2 a first control pneumatic pressure PC1 upon the initiation of each inspiratory phase and holding said pressure at a constant value until the end of said inspiratory phase, Time control means connected to said pressure generating means for determining an inspiratory time for each breathing cycle, independently of the volume to be delivered, by generating a second pneumatic pressure PC2 from said pressure PC1, said second control presssure PC2 being always less than PC1 during the inspiratory phase and increasing during that phase from a minimum value to a maximum value, and for determining an expiratory time for the breathing cycle by bleeding said first control pressure PC1 to atmosphere upon the termination of each said inspiratory phase and decreasing said second control pressure PC2 during the expiratory phase from said maximum value to said minimum value, ratio control means connected to said time control means for determining the ratio of inspiratory time to expiratory time for each breathing cycle, flow control means connected to said supply means and to said pressures PC1 and PC2 for providing breathing gas at a rate dependent upon the difference between first and second control pneumatic pressures, PC1 and PC2, a patient airway conduit connected to said flow control means for conducting said breathing gas and having exhalation valve means, exhalation valve control means connected to said exhalation valve means and to said time control means for synchronizing said exhalation valve with said inspiratory and expiratory phases, and volume control means connected to said supply means, said time control means and to said flow control means at a pressure P3 for determining, independently of time, the volume of breathing gas delivered in each inspiratory phase by (1) varying the flow rate whenever the time is varied so that the volume delivered during the set time remains unchanged and by (2) enabling additional variation of the flow rate for any one time setting for changing the volume delivered while the time remains unchanged.

17. The ventilator of claim 16 having a control conduit connecting said exhalation valve means to said patient airway conduit through a restriction and connecting said exhalation valve to said exhalation valve control means and wherein said exhalation valve control means comprises a diaphragm valve biased by a spring for venting said control conduit to atmosphere during said expiratory phase, said diaphragm valve being connected to said pressure PC1 and being closed by said pressure PC1 overcoming said bias spring when said pressure PC1 is present during said inspiratory phase.

18. The ventilator of claim 16 having means for operating humidifying, nebulizing, and high-pressure exhalation means through an operating conduit, comprising relay means connected to said pressure PC1 and to said pressure P3 for generating a pressure equal to PC1 and for conducting it to said operating circuit during said inspiratory phase and for bleeding said operating conduit to atmosphere during said expiratory phase.

19. A volume-cycled fully pneumatically operated pneumatic ventilator for connection to a supply of breathing gas, including in combination:

pneumatically operated pressure generating means for generating from said supply a first control pneumatic pressure PC1 upon the initiation of each inspiratory phase and holding said pressure at a constant value until the end of said inspiratory phase, pneumatically operated time control means connected to said pressure generating means for determining an inspiratory time for each breathing cycle, independently of the volume to be delivered, by generating a second pneumatic pressure PC2 from said pressure PC1, said second control pressure PC2 being always less than PC1 during the inspiratory phase and increasing during that phase from a minimum value to a maximum value, and for determining an expiratory time for the breathing cycle by bleeding said first control pressure PC1 to atmosphere upon the termination of each said inspiratory phase and decreasing saiD second control pressure PC2 during the expiratory phase from said maximum value to said minimum value, pneumatically operated ratio control means connected to said time control means for determining the ratio of inspiratory time to expiratory time for each breathing cycle, pneumatically operated flow control means connected to said supply and to said pressures PC1 and PC2 for providing breathing gas at a rate dependent upon the difference between first and second control pneumatic pressures, PC1 and PC2, a patient airway conduit connected to said flow control means and including exhalation valve means, pneumatically operated control means connected to said exhalation valve means and to said time control means for synchronizing said exhalation valve means with said inspiratory and expiratory phases, and pneumatically operated volume control means connected to said supply, said time control means, and to said flow control means for determining, independently of time, the volume of breathing gas delivered in each inspiratory phase by (1) varying the flow rate whenever the time is varied so that the volume delivered during the set time remains unchanged and by (2) enabling additional variation of the flow rate for any one time setting for changing the volume delivered while the time remains unchanged.

20. The ventilator of claim 19 wherein said time control means is connected to said pressure generating means for receiving said pressure PC1 by a parallel network of a check valve and a restriction, said check valve being opened during each inspiratory phase for rapid flow of gas at said PC1 pressure and closed during each expiratory phase, so that back flow to decrease said second control pressure PC2 is only through said restriction, which is sized to be effective at the shorter values of the time setting.

21. A volume-cycled, completely pneumatically operated pneumatic ventilator for connection to a supply of breathing gas, including in combination:

pneumatic time control means for determining the inspiratory time for each breathing cycle, independently of the volume of breathing gas to be delivered, by generating from said supply a first control pneumatic pressure PC1 upon the initiation of each inspiratory phase and by generating a second control pneumatic pressure PC2 from said pressure PC1, said first control pressure PC1 being present only during the inspiratory phase and constant during that time and dropping to atmospheric at the beginning of the expiratory phase, said second control pressure PC2 being always less than PC1 during the inspiratory phase and increasing during that phase from a minimum value above atmospheric to a maximum value, then decreasing during the expiratory phase from said maximum value to said minimum value, pneumatically operated ratio control means connected to said time control means for determining the ratio of inspiratory time to expiratory time for each breathing cycle, a patient airway conduit having exhalation valve means, pneumatically operated flow control means connected to said supply, said ratio control means, said time control means, said volume control means and said patient airway conduit, for providing breathing gas from said supply to said patient airway conduit at a rate dependent upon the difference between said first and second control pneumatic pressures PC1 and PC2, pneumatically operated control means connected to said exhalation valve means and to said time control means for synchronizing the operation of said exhalation valve means with said inspiratory and expiratory phases, and pneumatically operated volume control means connected to said supply and said time control means for determining, independently of time, the volume of breathing gas delivered in each inspiratory phase.

22. The ventilator of claim 21 wherein said time control means is connected to said ratio control means for receiving said pressure PC1 by a parallel network of a check valve and a restriction, said check valve being opened during each inspiratory phase for rapid flow of gas at said PC1 pressure and closed during each expiratory phase, so that back flow from said pressure PC2 during the expiratory phase is only through said restriction, which is sized to be effective at the shorter values of the time setting, said ventilator also having means comprising part of said ratio control means for bleeding said pressure PC1 to atmosphere at the beginning of said expiratory phase.

23. The ventilator of claim 21 having a manually actuated sigh valve connected to said time control means by a conduit into which said PC2 pressure is delivered, and a sigh chamber to which gas from said conduit is admitted when said manually actuated sigh valve is opened, thereby increasing the capacity of the timing system and lengthening both the inspiratory and expiratory phases proportionately, with proportional increase in the volume of breathing gas during said lengthened inspiratory phase, while said manually actuated valve is held open.

24. A fully pneumatic volume-cycled pneumatic ventilator, providing inspiratory phases alternating with expiratory phases, including in combination:

supply means for supplying a breathing gas at a first regulated pressure P1, regulator means connected to said supply means and having an outlet for said gas at a second, lower, pressure P2, a PC1 conduit, a PC2 conduit, a cycle generator having a housing with an inlet connected to the outlet from said regulator means and having a first diaphragm assembly with two diaphragms of different effective areas, with atmospheric pressure between them, a first seat at one end bounded by the smaller area diaphragm of said first diaphragm assembly, adapted to close said inlet or to open it to a first chamber, said first chamber having an outlet, a second chamber at the other end bounded by the larger area diaphragm of said first diaphragm assembly and having a port connected to said PC2 conduit, a compression spring in said second chamber urging said first diaphragm assembly to close said inlet, and an inspiratory-time-to-expiratory-time ratio determining screw assembly for regulating the compression of said spring, a fixed-orifice bleed connected to the outlet of said first chamber, said cycle generator also having a second diaphragm assembly with two diaphragms of different effective areas and a second seat, a third chamber at one end bounded by the larger area diaphragm of said second diaphragm assembly and having an inlet connected to the outlet from said first chamber and an outlet leading to said PC1 conduit via a spring-urged check valve which transmits the pressure of said first chamber to said PC1 conduit during each inspiratory phase and prevents back flow from said PC1 conduit into said third chamber at end of each expiratory phase, when said first seal closes said inlet to said cycle generator and while said third chamber bleeds to atmosphere through said fixed orifice bleed, a fourth chamber between the diaphragms of said second diaphragm assembly having a port connected to said PC2 conduit, and a fifth chamber at the other end bounded by the smaller area of diaphragm of said second diaphragm assembly having an inlet connected to said PC1 conduit, normally closed by said second seat and an outlet vented to atmosphere, for venting said PC1 conduit during each said expiratory phase, an inspiratory-time-determining valve, having an inlet connected to said PC1 conduit and an outlet connected to said PC2 conduit, for supplying said PC2 conduit with the gas at a varying pressure PC2 always lower than the pressure PC1 during each inspiratory phase, said time-determining valve having a logarithmically shaped stem and orifice and time-setting means for determining the position of said stem relative to said orifice and therefore the flow rate from said PC1 conduit to Said PC2 conduit, said PC2 pressure building up continuously during each said inspiratory phase to a maximum value set by said ratio-determining screw assembly, and continuously decreasing during said expiratory phase by bleeding through said PC1 conduit to atmosphere until it reaches a minimum value which is a set amount lower than said maximum value, the set amount being determined by the ratio of the effective areas of the two diaphragms of said first diaphragm assembly, an inspiratory volume-determining valve, having an inlet connected to said supply means, an outlet at a reduced pressure P3 and at a flow determined by the relative position of a plug within an orifice, the plug being shaped so that its position sets the area of passage according to a logarithmic function, first flow-setting means determining the position of said plug relative to its orifice entirely independently of said time-setting means and second flow-setting means also determining the position of said plug relative to its orifice in inverse ratio to the setting of said time, so that the volume delivered by said volume-determining valve remains the same when the time determining means alone is varied, a flow controller having a third diaphragm assembly of three diaphragms including two outer diaphragms of equal effective area and a central diaphragm of smaller effective area and having a third seat at one end, a sixth chamber at one end of said third diaphragm assembly having an outlet orifice toward and away from which said third seat moves, flow through said outlet orifice being varied according to the position of said third seat, said sixth chamber having an inlet connected to the outlet from said volume-determining valve at said pressure P3, said flow controller also having a seventh chamber adjacent to said sixth chamber, between said first outer diaphragm and the central diaphragm with a port connected to said PC2 conduit, an eighth chamber adjacent to said seventh chamber between the central diaphragm and the second outer diaphragm with a port connected to said PC1 conduit, and a ninth chamber at the opposite end of said diaphragm assembly from said sixth chamber with a port connected to said supply pressure P1, a compression spring in said ninth chamber bearing on said third diaphragm assembly, and means for setting the compression of said compression spring, whereby as said pressure PC2 increases during the inspiratory phase and said pressure PC1 remains constant, the outflow from said outlet orifice decreases from a maximum at the start of the inspiratory phase to a minimum at the end of the phase, and whereby the flow is shut-off during the expiratory phase as PC1 is at atmospheric pressure and PC2 is greater than PC1, a patient airway conduit connected to said outlet orifice of said flow controller, an exhalation valve in said patient airway conduit, and exhalation valve control means for said exhalation valve connected thereto and to said cycle generator for synchronizing the opening and closing of said exhalation valve with the initiation, respectively, of said expiratory and inspiratory phases.

25. The ventilator of claim 24 having a control conduit connecting said exhalation valve to said patient airway conduit through a restriction and connecting said exhalation valve to said exhalation valve control means and wherein said exhalation valve control means is connected to said PC1 conduit and comprises a diaphragm valve biased by a spring for venting said control conduit to atmosphere during said expiratory phase, said diaphragm valve being closed by said pressure PC1 overcoming said bias spring when said pressure PC1 is present during said inspiratory phase.

26. The ventilator of claim 24 having means for operating humidifying, nebulizing, and high-pressure exhalation means through an operating conduit, comprising relay means connected to said PC1 conduit and to the outlet of sAid inspiratory volume-determining valve at said pressure P3 for generating a pressure equal to PC1 and for conducting it to said operating conduit during said inspiratory phase and for bleeding said operating conduit to atmosphere during said expiratory phase.

27. The ventilator of claim 24 wherein the inlet to said inspiratory-time-determining valve is connected to said PC1 conduit by a parallel network of a check valve and a restriction, said check valve being opened during each inspiratory phase for rapid flow of gas and closed during each expiratory phase, so that back flow is only through said restriction, the restriction being sized to be effective at the shorter expiratory times for which the ventilator can be set.

28. The ventilator of claim 24 having an adjustable pressure relief valve connected to said airway conduit for venting pressure to atmosphere when it reaches a preset value.

29. The ventilator of claim 24 having a vacuum release valve connected to said airway conduit for admitting air to said airway conduit if the vacuum therein exceeds a predetermined value.

30. The ventilator of claim 24 having a manually actuated sigh valve connected to said PC2 conduit and a sigh chamber to which gas from said PC2 conduit is admitted when said manually actuated valve is opened, thereby increasing the capacity of the timing system and lengthening both the inspiratory and expiratory phases proportionately, with proportional increase in volume, while said manually actuated valve is held open.

31. The ventilator of claim 24 having override means for actuation by a patient able to initiate a new inspiratory phase before completion of a controlled expiratory phase, comprising means connected to said patient airway conduit for sensing a patient-induced vacuum of given value, signal supply means for producing a pressure signal when said given value is sensed, and means for venting said PC2 pressure conduit from its then pressure to its minimum pressure upon application of said signal thereto.

32. The ventilator of claim 31 wherein said means for sensing comprises a housing, a fourth diaphragm assembly in said housing having two diaphragms, one large area diaphragm and one small area diaphragm, with a tenth chamber between them connected to said airway conduit, the end with large area diaphragm of said fourth diaphragm assembly being vented to the atmosphere, the other end being open to an eleventh chamber and having a fourth seat, spring means in said tenth chamber, and sensitivity control means for setting the pressure exerted by said spring means against said diaphragm assembly, a detector assembly having a fifth diaphragm assembly open at one end to said eleventh chamber and having a tubular extension that provides an axial conduit and is opened and closed by said fourth seat, spring means acting on said fifth diaphragm assembly to urge it to open said axial conduit, twelfth chamber on the opposite end of said fifth diaphragm assembly, the motion of said fifth diaphragm assembly being limited to a fixed amount by internal configuration of said eleventh and twelfth chambers, a port venting said eleventh chamber to atmosphere, a passage through said fifth diaphragm assembly into said twelfth chamber from said axial conduit, an inlet connected to said P2 conduit and having a restricted orifice leading into said twelfth chamber, and a port connecting said twelfth chamber to said signal supply means.

33. The ventilator of claim 32 having a relay for said detector assembly, comprising a sixth diaphragm assembly having a pair of diaphragms of equal effective area defining a thirteenth chamber on one side of said sixth diaphragm assembly, connected to the twelfth chamber for maintaining the same pressure as in said twelfth chamber, a fourteenth chamber between said diaphragms and vented to atmosphere, and a fifteenth chamber on the other side of said sixth diaphragm assembly, said sixth diaphragm assembly having an axial opening and a Passageway opening from said fifteenth chamber into said fourteenth chamber, a sixteenth chamber joined to said fifteenth chamber by a port, a poppet for opening and closing said port and having an extension for engaging said axial opening and closing it when engaged by said sixth diaphragm assembly, said sixth diaphragm assembly operating when in contact with said poppet to open said port, and an inlet into said sixteenth chamber connected to said P2 pressure, and a signal conduit connecting said fifteenth chamber to said means for venting PC2.

34. A fully pneumatic pressure-cycled ventilator including in combination:

supply means for supplying a breathing gas at a first regulated pressure , regulator means connected to said supply means and having an outlet for said gas at a second, lower, pressure P2, an airway pressure sensor and controller comprising a housing, a first diaphragm assembly in said housing having a large first diaphragm, a smaller diaphragm, a first chamber between them having a port, a second chamber on the other side of said large first diaphragm, vented to the atmosphere, a third chamber on the other side of said second diaphragm, a seat on said first diaphragm assembly in said third chamber, a first spring in said first chamber bearing against said first diaphragm assembly, and a second, lighter, spring bearing on said large diaphragm in said second chamber, sensitivity control means for varying the pressure of said first spring against said first diaphragm assembly, a second diaphragm assembly having a pair of diaphragms of different effective areas and open at one end to said second chamber, with a third spring in said second chamber urging said second diaphragm assembly away from said first diaphragm assembly, a fourth chamber between said pair of diaphragms having a port, the other end of said second diaphragm assembly being open to atmospheric pressure, said first and second diaphragm assemblies each having extensions causing said second diaphragm assembly to exert force on said first diaphragm assembly when pressure in said fourth chamber is sufficient to overcome the force of said third spring and the pressure in said first chamber, a detector assembly having a third diaphragm assembly open to said third chamber and carrying a tubular extension that provides an axial conduit having an end facing said seat and opened and closed by said seat, a fourth spring acting on said third diaphragm assembly to urge it to open said axial conduit away from said seat, a fifth chamber on the opposite side of said third diaphragm assembly from said third chamber, the motion of said third diaphragm assembly being limited to a fixed amount by internal configurations of said third and fifth chambers, a port venting said third chamber to atmosphere, a passage through said third diaphragm assembly into said fifth chamber from said axial conduit, an inlet connected to the outlet from said regulator means at pressure P2 and having a restricted orifice leading into said fifth chamber, and an outlet port from said fifth chamber, a control conduit having its pressure controlled by and identical to that of said outlet port of said fifth chamber, a second pressure regulator for setting the pressure applied to said fourth chamber, having an inlet connected to said control conduit and having an outlet, a conduit connected to said outlet of said second pressure regulator having a fixed bleed to atmosphere and connected to the port to said fourth chamber, a flow valve, having an inlet connected to said supply means at said pressure P1, a plug, an orifice, an outlet for gas at a reduced pressure P3 and at a flow determined by the relative position of said plug and said orifice, and flow-setting means determining the position of said plug relative to said orifice, a flow controller having a fourth diaphragm assembly having three diaphragms including two outer diaphragms of equal effective area and a centRal diaphragm of smaller effective area and having a second seat at one end, a sixth chamber at one end of said fourth diaphragm assembly having an outlet orifice toward and away from which said second seat is moved, flow through said outlet orifice being varied according to the position of said second seat, said sixth chamber having an inlet connected to the outlet from said flow valve at said pressure P3, said flow controller also having a seventh chamber adjacent to said sixth chamber, between said first outer diaphragm and the central diaphragm of said fourth assembly with a port connected to atmosphere, an eighth chamber adjacent to said seventh chamber between the central diaphragm and second outer diaphragm with a port connected to said control conduit, and a ninth chamber at the opposite end of said fourth diaphragm assembly from said sixth chamber, with a port connected to said supply pressure P1, a compression spring in said ninth chamber bearing on said fourth diaphragm assembly, and means for setting the compression of said compression spring, a patieairway conduit connected to said outlet orifice of aid flow controller and connected to the port of said first chamber, an exhalation valve in said patient airway conduit, and exhalation valve control means connected to said control conduit for opening said exhalation valve during each said expiratory phase and closing it during each said inspiratory phase.

35. The ventilator of claim 34 having a second control conduit connecting said exhalation valve to said patient airway conduit through a restriction and connecting said exhalation valve to said exhalation valve control means, and wherein said exhalation valve control means comprises a diaphragm valve biased by a spring for venting said second control conduit to atmosphere during said expiratory phase, said diaphragm valve being closed by said control pressure overcoming said bias spring when said control pressure PC1 is above atmospheric during said inspiratory phase.

36. The ventilator of claim 34 having means for operating humidifying, nebulizing, and high-pressure exhalation means through an operating conduit, comprising relay means connected to said control pressure and to said pressure P3 for generating a pressure equal to said control pressure and for conducting it to said operating conduit during said inspiratory phase and for bleeding said operating conduit to atmosphere during said expiratory phase.

37. The ventilator of claim 34 having pneumatic means connected to said control pressure for determining a constant time interval, means for beginning said time interval at the beginning of each said expiratory phase, and means actuated upon completion of said time interval for initiating a new said inspiratory phase unless said inspiratory phase has already been started by patient effort during said time interval, said new inspiratory phase being subject to the stated conditions of the control pressure generating means.

38. The ventilator of claim 34 having an adjustable pressure relief valve connected to said airway conduit for venting pressure to atmosphere when it reaches a preset value.

39. The ventilator of claim 34 having a vacuum release valve connected to said airway conduit for admitting air to said airway conduit if the vacuum therein exceeds a predetermined value.

40. The ventilator of claim 34 having a relay for said detector assembly, comprising a fifth diaphragm assembly having a pair of diaphragms of equal effective area defining a tenth chamber on one end, connected to said fifth chamber for maintaining the same pressure as in said fifth chamber, an eleventh chamber between said diaphragms and vented to atmosphere, and a twelfth chamber on the other end, said fifth diaphragm assembly having an axial opening in said twelfth chamber leading to a passageway opening into said eleventh chamber, and a patient airway chamber joined to said twelftH chamber by said port, a poppet for opening and closing said port and having an extension for engaging said axial opening and closing it when engaged by said fifth diaphragm assembly, said fifth diaphragm assembly operating when in contact with said poppet to open said port, and an inlet into said thirteenth chamber connected to said P2 pressure, and an outlet connecting said twelfth chamber to said control conduit.

41. A ventilator operated solely by pneumatics and capable of both pressure-cycled and volume-cycled operation, including in combination:

supply means for supplying a breathing gas at a first regulated pressure P1, pneumatically operated regulator means connected to said supply means and having an outlet for said gas at a second, lower, pressure P2, pneumatically operated pressure reduction and flow-rate determining means having an inlet connected to said supply means at the pressure P1 and having an outlet for gas at pressure P3, pneumatically actuated flow control means having an inlet connected to said flow-rate determining means and having an outlet and pneumatically controlled means for opening said outlet only when a first control pressure PC1 is above a second control pressure PC2 and for then supplying said outlet with breathing gas from its said inlet at a flow rate dependent on the instantaneous difference between said first and second control pressures, a patient airway conduit connecting said outlet of said flow control means to a patient to be ventilated, a master operations switch connected to said regulator means and having a first '"'"''"'"''"'"''"'"'volume-cycled'"'"''"'"''"'"''"'"' position and a second '"'"''"'"''"'"''"'"'pressure-cycled'"'"''"'"''"'"''"'"' position, first pneumatically operated pressure generating means connected to said master operations switch for generating from said pressure P2 the pressure PC1 at a constant value, for delivering said pressure PC1 to said flow control means as said first control pressure when said switch is in '"'"''"'"''"'"''"'"'volume-cycled'"'"''"'"''"'"''"'"' position, pneumatically operated time control means connected to said first pressure generating means for determining an inspiratory time for each breathing cycle, independently of the volume to be delivered, by generating the pressure PC2 from said pressure PC1 at a value lower than PC1 during said inspiratory phase and sending it to said flow control means as said second control pressure PC2 by causing said pressure PC1 to be present only during the inspiratory phase and to be constant during that phase, said pressure PC2 increasing continually during that phase from a minimum value to a maximum value, always less than said pressure PC1 during said inspiratory phase and for determining an expiratory time for a breathing cycle, by bleeding said first control pressure PC1 to atmosphere upon the termination of each said inspiratory phase and by decreasing continually said pressure PC2 during the expiratory phase from said maximum value to said minimum value, pneumatically operated ratio control means connected to said time control means for determining the ratio of inspiratory time to expiratory time for each breathing cycle, pneumatically operated volume-control means connected to said time control means and to said flow-rate determining means for determining, independently of time, the volume of breathing gas to be delivered in each inspiratory phase of said volume-cycled mode, second pneumatically operated pressure generating means connected to said regulator means and to said switch when said switch is in '"'"''"'"''"'"''"'"'pressure cycled'"'"''"'"''"'"''"'"' position, for generating a pressure PC3 when the pressure in said patient airway conduit drops below a first predetermined level, indicating an attempt by the patient to initiate an inspiratory phase of a breathing cycle, pnuematically operated means for ceasing generation of said pressure PC3 and for bleeding it to atmosphere when the pressure in said airway conduit attains a second predetermined level Well above said first predetermined level, said operations switch acting in said '"'"''"'"''"'"''"'"'pressure-cycled'"'"''"'"''"'"''"'"' position to connect said pressure PC3 to said flow control means as said first control means and for bleeding said pressure PC2 to atmospheric and for disconnecting said pressure PC1 from said flow control means, said operations switch acting in said '"'"''"'"''"'"''"'"'volume-cycled'"'"''"'"''"'"''"'"' position to disconnect said pressure PC3 from said flow control means.

42. The ventilator of claim 41 having an exhalation valve in said patient airway conduit, and exhalation valve control means for opening said exhalation valve during each said expiratory phase and closing it during each said inspiratory phase.

43. The ventilator of claim 42 having a control conduit connecting said exhalation valve to said patient airway conduit through a restriction and connecting said exhalation valve to said exhalation valve control means and wherein said exhalation valve control means is connected by said switch to said PC1 in the '"'"''"'"''"'"''"'"'volume-cycled'"'"''"'"''"'"''"'"' position and to said PC3 in the '"'"''"'"''"'"''"'"'pressure-cycled'"'"''"'"''"'"''"'"' position and comprises a diaphragm valve biased by a spring for venting said control conduit to atmosphere during said expiratory phase, said diaphragm valve (a) being closed, when said master operations switch is in '"'"''"'"''"'"''"'"'volume-cycled'"'"''"'"''"'"''"'"' position, by said pressure PC1 overcoming said bias spring when said pressure PC1 is present during said inspiratory phase and (b) being closed, when said master operations switch is in '"'"''"'"''"'"''"'"'pressure-cycled'"'"''"'"''"'"''"'"' position by said pressure PC3 overcoming said bias spring when PC3 is above atmospheric during said inspiratory phase.

44. The ventilator of claim 41 having pneumatically operated means for operating humidifying, nebulizing, and high-pressure exhalation means through an operating conduit, comprising pneumatic relay means, connected by said switch, when in the '"'"''"'"''"'"''"'"'volume-cycled'"'"''"'"''"'"''"'"' position to said pressure PC1 and, when in the '"'"''"'"''"'"''"'"'pressure-cycled'"'"''"'"''"'"''"'"' position to said pressure PC3, said relay means in both modes being connected to said pressure P3, for generating a pressure equal to PC1 or PC3, according to the position of said switch, and for conducting it to said operating conduit during said inspiratory phase and for bleeding said operating conduit to atmosphere during said expiratory phase.

45. The ventilator of claim 41 having pneumatic means connected to said pressure PC3 for determining a constant time interval, pneumatically operated means for beginning said time interval at the beginning of each said expiratory phase, and pneumatically operated means actuated upon completion of said time interval for initiating a new said inspiratory phase unless said inspiratory phase has already been started by patient effort during said time interval, said new inspiratory phase being subject to the stated conditions of the second pressure generating means.

46. The ventilator of claim 41 having an adjustable pressure relief valve connected to said patient airway conduit for venting pressure to atmosphere, when it reaches a preset value.

47. The ventilator of claim 41 having a vacuum release valve connected to said patient airway conduit for admitting air to said airway conduit if the vacuum therein exceeds a predetermined value.

48. The ventilator of claim 41 having a manually actuated sigh valve connected to said PC2 conduit and a sigh chamber to which gas from said PC2 conduit is admitted when said manually actuated valve is opened, thereby increasing the capacity of the timing system and lengthening both the inspiratory and expiratory phases proportionately, with proportional increase in volume, while said manually actuated valve is held open in said '"'"''"'"''"'"''"'"'volume-cycled'"'"''"'"''"'"''"'"' mode.

49. The ventilator of claim 41 having pneumatically operated override means for actuation in the '"'"''"'"''"'"''"'"'volume-cycled'"'"''"'"''"'"''"'"' mode by a patient able to initiate a nEw inspiratory phase before completion of a controlled expiratory phase, comprising a signal conduit for transmitting a pressure signal from said second pressure generating means at pressure PC3 when the pressure in said patient airway conduit drops below said first predetermined level and means connected to said signal conduit for venting said PC2 pressure conduit from its then pressure to its minimum pressure upon receipt of said signal.

50. A fully pneumatically operated ventilator of the type free from electric circuits and supplying breathing gas to a patient via an airway conduit during an inspiratory phase and stopping the supply during an expiratory phase, characterized by incorporating two modes of operation, (a) a volume-cycled mode in which the ventilator supplies a predetermined volume of breathing gas to the airway conduit over a predetermined time during the inspiratory phase and then is actuated to the expiratory phase for a predetermined time, and (b) a pressure cycled mode in which the ventilator supplies the breathing gas to the airway conduit whenever the pressure in the airway conduit drops below a predetermined level and stops the supply whenever a predetermined higher pressure is attained in the airway conduit, said ventilator comprising gas inlet means shared by both said modes, gas regulator means connected to said inlet means and shared by both said modes, pneumatically operated flow control means shared by both said modes and separately connected to said inlet means and to said gas regulator means for controlling the rate of flow of gas to the patient, gas outlet means connected to said flow control means and shared by both said modes, a pneumatically operated exhalation valve shared by both said modes, in said airway conduit, pneumatically actuated pneumatic control switch means shared by both said modes and separately connected to said inlet means and to said regulator means and connected to said exhalation valve for operating said exhalation valve, pneumatically operated pressure sensing means shared by both said modes and connected to said outlet means and to said regulator and to said flow control means for changing said ventilator from an expiratory phase to an inspiratory phase when the patient makes an effort of a predetermined negative pressure sensed by said sensing means, and a two-position manually operated master operation switch for selecting which of said two modes is to be used at any one time, said master operation switch having a single handle for switching from one mode to the other by a single simple movement.

51. The ventilator of claim 50 characterized by said pressure-cycled mode comprising a flow-rate-determiner and pressure-reducer means having an inlet connected to the supply of breathing gas, said flow control means having an inlet connected to said flow-rate-determiner and pressure-reducer means and having pneumatic control means for opening its outlet when the control pressure is above a predetermined minimum pressure and for closing it when the control pressure drops below the predetermined minimum pressure, said patient airway conduit connecting the outlet of the flow control means to the patient to be ventilated through said outlet means, and control pressure generator means connected directly to the supply, to the flow control means, and to the patient airway conduit, for generating the control pressure when the pressure in said airway conduit drops below a first predetermined level, indicating an attempt by the patient to initiate an inspiratory phase of a breathing cycle, and for ceasing generation of the control pressure and for bleeding said control pressure to atmosphere when the pressure in said airway conduit attains a second predetermined level well above the first predetermined level, thereby initiating the expiratory phase of the breathing cycle.

52. The ventilator of claim 51 characterized in that said control pressure genErator means includes a first sensor for sensing the first predetermined level, a lock actuated by said first sensor for locking the control pressure generator means in generating position upon attainment of the first predetermined level, a second sensor for sensing the second predetermined pressure, and an unlocker actuated by the second sensor for unlocking said lock upon attainment of the second predetermined level.

53. The ventilator of claim 51 characterized by a pneumatic timer connected to the control pressure for determining a constant time interval, a first initiator for beginning the constant time interval at the beginning of each expiratory phase, and a second initiator actuated upon completion of the time interval for initiating a new said inspiratory phase unless the inspiratory phase has already been started by patient effort during said time interval, the new inspiratory phase being subject to the stated conditions of the control pressure generator means.