Piston actuated, pilot valve operated breathing regulator

• US 4,436,090 A
• Filed: 08/11/1981
• Issued: 03/13/1984
• Est. Priority Date: 01/22/1979
• Status: Expired due to Term

• Current Assignee: Phillip H. Darling
• Original Assignee: Phillip H. Darling
• Inventors: Darling, Phillip H.
• Primary Examiner(s): Cohen, Lee S.
• Application Number:
  US06/291,998
• Time in Patent Office: 945 Days
• Field of Search: 128/204.24, 128/204.25, 128/204.26, 128/204.29, 128/205.11, 128/205.19, 128/205.24, 137/491, 137/492, 137/489
• US Class Current: 128/204.26
• CPC Class Codes: A61M 16/0009 with sub-atmospheric pressure, e.g. during expiration
• CPC Class Codes: A61M 16/107 in the inspiratory path
• CPC Class Codes: A61M 16/20 Valves specially adapted to medical respiratory devices
• CPC Class Codes: A61M 16/208 Non-controlled one-way valves, e.g. exhalation, check, pop-off non-rebreathing valves
• CPC Class Codes: A61M 16/209 Relief valves
• CPC Class Codes: Y10T 137/7766 Choked passage through main valve head

Abstract

A breathing regulator includes a pressure-responsive piston which acts directly on a valve seat to open a pressurized gas pilot valve during inhalation. The same piston provides an outlet for exhalation. The piston is moved to open the pilot valve by inhalation suction. A one-way valve automatically blocks the exhalation path during inhalation. The outlet for the pressurized gas provides an injector nozzle effect to reduce the effort required to actuate the valve during inhalation. The preferred embodiment of the invention incorporates the regulator in a resuscitator or respirator for medical applications. In this embodiment, a mechanism is included for controlling the amount of inhalation back pressure in the patient'"'"'s air passages which will close the pressurized gas valve and open the exhaust passage in the regulator. This mechanism includes an adjustable spring-loaded pressure plate on the external side of the piston. The inhalation pressure adjusting mechanism also provides for positive end expiratory pressure. In another embodiment, the basic regulator is adapted for use as a breathing regulator for high altitude aviation. In this embodiment, the invention includes aneroid bellows which close an ambient air inlet when a predetermined altitude is reached, so that breathing is exclusively from a pressurized gas source. The aviation embodiment also provides for pressurized breathing.

Claims

1. A device for the regulation of a user'"'"'s breathing from a source of pressurized gas, comprising:

a housing having passage means for conducting said pressurized gas to said user;

a valve body in said housing, said valve body having a pressurized gas inlet and a gas outlet, said outlet communicating with said passage means;

a first pressurization chamber in said body, communicating with said inlet;

valving means, moveable within said body, for controllably opening and closing said outlet, said valving means having first and second surfaces, said first surface confronting said first chamber, said second surface having a larger area than said first surface;

a second pressurization chamber communicating with said first pressurization chamber, said second surface of said valving means confronting said second chamber, said valving means being moveable in opposite directions within said body in response to the force differential between said first and second surfaces so that said valving means closes said gas outlet when the force on said second surface, equal to the pressure on said second surface times the area of said second surface, is greater than the force on said first surface, equal to the pressure on said first surface times the area of said first surface, thus closing said gas outlet when the pressures in said first and second pressurization chambers are equal, and said valving means opens said gas outlet when the force on said first surface is greater than the force on said second surface;

a pilot valve having pilot passage means for venting gas from said second chamber to reduce the pressure in said second chamber with respect to the pressure in said first chamber so that said valving means opens said outlet;

pilot passage closure means, slideably moveable between a first position and a second position, for closing said pilot passage means in said first position and opening said pilot passage means in said second position;

pilot valve actuating means, attached to said pilot passage closure means, and forming a pressure interface between the interior and exterior of said housing, for moving said closure means from said first position to said second position in response to an inhalation-induced reduction in pressure on the interior side of said interface with respect to the pressure on the exterior side of said interface; and

exhalation outlet means from said housing.

2. The device of claim 1, wherein said pilot valve actuating means comprises:

a piston which is moveable within said housing; and

means for providing a substantially frictionless seal between said piston and said housing.

3. The device in claim 1, further comprising:

means for adjustably diluting said pressurized gas in said passage means with ambient air from the atmosphere external to said housing.

4. The device of claim 3, wherein said diluting means comprises:

an air inlet into said housing;

a fixed apertured member in said housing; and

means for variably obstructing the flow of air from said air inlet through said apertured member.

5. The device of claim 4, wherein said variable flow obstructing means comprises:

a moveable apertured member connected to said housing and located between said fixed apertured member and said air inlet.

6. The device of claim 4, wherein said variable flow obstructing means comprises:

aneroid means in said housing proximate said air inlet, for expanding to increasingly obstruct said air inlet in response to decreasing ambient pressure.

7. The device of claim 1, further comprising:

an air inlet into said housing; and

automatic valving means for closing said air inlet when said pressurized gas in said pressurized gas inlet is at or above a first predetermined pressure and opening said air inlet when the pressure of said pressurized gas in said pressurized gas inlet is below said first predetermined pressure.

8. The device of claim 7, wherein said automatic valving means additionally opens said air inlet when the pressure of said pressurized gas in said passage means is at or above a second predetermined pressure, so that said air inlet provides an over-pressure relief outlet.

9. The device of claim 1, wherein said pilot valve actuating means moves said closure means from said second position to said first position in response to an increase in pressure on the interior side of said pressure interface with respect to the pressure on the exterior side of said interface.

10. The device of claim 9, further comprising:

breathing pressure adjustment means, acting on said pilot valve actuating means for both (a) providing positive pressure breathing by said user during inhalation, and (b) maintaining a predetermined positive and expiratory pressure is provided.

11. The device of claim 10, wherein said breathing pressure adjustment means comprises:

pressurization means engageable with the exterior side of said pressure interface, for controllably applying a presure to said interface to vary said pressure on the interior side of said pressure interface which causes said pilot passage closure means to move between said second position and said first position.

12. The device of claim 11, wherein said exhalation outlet means is through said pressure interface, and said pressurization means closes said exhalation outlet means during inhalation.

13. The device of claim 11, further comprising:

means, responsive to the pressure at said gas outlet for controllably engaging said pressurization means against the exterior side of said pressure interface.

14. The device of claim 9, further comprising:

pressurized inhalation means for providing positive pressure inhalation at a constant absolute pressure level relative to decreasing ambient pressure.

15. The device of claim 14, wherein said pressurized inhalation means comprises:

pressure-responsive means for increasing said predetermined pressure which cause said pilot passage closure means to move between said second position and said first position as said ambient pressure decreases.

16. The device of claim 15, wherein said pressure-responsive means comprises:

first expandable means for expanding in response to said user'"'"'s inhalation; and

second expandable means for gradually expanding in response to decreasing ambient pressure, the expansion of said first and second expandable means pressurizing the external side of said pressure interface.

17. The device of claim 1, further comprising:

means on said valve body and in communication with said pressurized gas inlet, for providing vacuum assisted exhalation using the Coanda effect.

18. A device for regulating a user'"'"'s breathing from a source of pressurized gas, comprising:

a housing having passage means for conducting said pressurized gas to said user;

a valve body in said housing and having an inlet and an outlet for said pressurized gas, said outlet communicating with said passage means;

main valving means moveable within said valve body, for opening and closing said outlet;

pilot valving means, slideably moveable between an open and a closed position, for controllably actuating said main valving means against the force of said pressurized gas;

pressure-responsive means, attached to the low pressure side of said pilot valving means and providing a pressure interface between the interior and exterior of said housing, for moving said pilot valving means to said open position when the pressure on the interior side of said interface drops below the pressure on the exterior side of said interface by a first predetermined amount;

means for moving said pilot valving means to said closed position when the pressure on the interior side of said pressure interface rises by a second predetermined amount in response to an increase in pressure in said passage means as a result of the end of inhalation; and

pressurization means, engageable with the exterior side of said pressure interface, for adjutably applying a pressure to said exterior side to vary said second predetermined amount of pressure.

19. The device of claim 18, additionally comprising:

breathing pressure adjustment means, acting on said pressure-responsive means, for selectably (a) providing positive pressure inhalation, and (b) maintaining a predetermined positive pressure in said passage means so that positive end expiratory pressure is provided.

20. The device of claim 19, wherein said breathing pressure adjustment means comprises:

means for independently controlling the pressure of said positive pressure breathing and said predetermined positive pressure at the end of exhalation.

21. The device of claim 19, wherein said pressurization means further comprises:

aneroid means, responsive to the pressure of said pressurized gas and the pressure at said outlet, for controllably actuating said breathing pressure adjustment means.

22. The device of claim 18, wherein said pressurization means comprises:

pressurized inhalation means for providing positive pressure inhalation at a constant absolute pressure level relative to decreasing ambient pressure.

23. The device of claim 22, wherein said pressurized inhalation means comprises:

aneroid means for increasing said second predetermined pressure with decreasing ambient pressure.

24. The device of claim 23, wherein said aneroid means comprises:

first aneroid means for expanding in response to said user'"'"'s inhalation; and

second aneroid means for gradually expanding in response to decreasing ambient pressure, the expansion of said first and second aneroid means applying a pressure to the exterior side of said pressure interface to vary said second predetermined pressure.

25. The device of claim 18, further comprising:

rigid connecting means for attaching said pressure-responsive means to said pilot valving means to provide unitary, straight-line motion of said pilot valving means and said pressure-responsive means.

26. The device of claim 18, further comprising:

means responsive to the ambient pressure external to said housing and acting on said main valving means, for varying the amount which said pressurized gas outlet is opened by said main valving means in response to changes in said ambient pressure.

27. The device of claim 18, wherein said main valving means comprises:

a pressurized gas outlet occluding portion; and

means for generating a partial pressure recovery proximate said occluding portion when said pressurized gas flows through said outlet past said main valving means as said main valving means opens said outlet, so that the fluttering of said main valving means is substantially eliminated.

28. In a device for the regulation of a user'"'"'s breathing from a source of pressurized gas, of the type having a housing which includes a passage for conducting said pressurized gas from said source to said user, said passage comprising a main valve, moveable within said housing, for regulating the flow of said pressurized gas, and a pilot valve orifice for controlling movement of said main valve against the force exerted by said pressurized gas, the improvement comprising:

pilot valve closure means movable in a straight line path for selectively blocking said orifice;

pressure-responsive means in said housing for actuating by straight-line motion said pilot valve closure means; and

pressurization means, selectably acting on said pressure-responsive means, for (a) effecting positive pressure breathing during inhalation, and (b) maintaining a predetermined positive pressure in said user'"'"'s air passages at the end of exhalation, so that positive and expiratory pressure is provided.

29. The device of claim 28, wherein said pressure-responsive means comprises:

a piston providing a pressure interface between the interior and exterior of said housing and moveable from a first position to a second position within said housing when the pressure on the exterior side of said pressure interface exceeds the pressure on the interior side of said pressure interface by a predetermined amount;

means engaging said pilot valve closure means for closing said pilot valve orifice when the pressure differential from the exterior side to the interior side of said pressure interface is less than said predtermined amount; and

connecting means for rigidly connecting said piston and said pilot valve closure means for closing said pilot valve orifice when the pressure differential from the exterior side to the interior side of said pressure interface is less than said predetermined amount so that the movement of said piston from said first position to said second position opens said pilot valve closure means, and the closing of said pilot valve orifice by said pilot valve closure means moves said piston from said second position to said first position.

30. The device of claim 29, further comprising:

sealing means for providing a substantially frictionless seal between said piston and said housing as said piston moves between said first and second positions; and

outlet means for permitting exhalation through said pressure interface.

31. The device of claim 30, wherein said outlet means comprises:

an aperture in said pressure interface; and

resilient valving means for sealing said aperture during inhalation and opening said aperture during exhalation.

32. The device of claim 29, wherein said pressurization means comprises:

means for adjustably exerting a pressure on the exterior side of said pressure interface.

33. The device of claim 29, wherein said pressurization means comprises:

pressure adjustment means for adjustably increasing the pressure on the exterior side of said pressure interface during inhalation to increase the pressure required on the interior side of said pressure interface to close said pilot valve closure means.

34. The device of claim 33, wherein said pressurization means further comprises:

second pressure adjustment means for adjustably applying pressure to the exterior side of said pressure interface during exhalation to cause said piston to move from said first to said second position when the difference between said applied pressure and said user'"'"'s expiratory pressure is greater than said predetermined pressure differential, so that said pilot valve closure means is opened.

35. A device for regulating a user'"'"'s breathing from a source of pressurized gas comprising:

a housing having passage means for conducting said pressurized gas to said user;

a valve body in said housing and having inlet and outlet means for said pressurized gas, said outlet means communicating with said passage means;

pressurized gas valving means, moveable between a firs and a second position in said valve body, for respectively closing and opening said outlet means;

pressure responsive means, including a pressure interface between the interior and exterior of said housing for both (a) moving said pressurized gas valving means between said first and second positions in response to said user'"'"'s inhalation, and (b) providing an exhalation outlet from said housing in response to said user'"'"'s exhalation;

means for maintaining said exhalation outlet closed when the pressure in the interior of said housing is below a specified pressure; and

means for adjustably applying pressure to said pressure interface on the side exterior of said housing to adjust said specified pressure required to open said exhalation outlet.

36. The device of claim 35, wherein said pressure responsive means comprises:

a piston having an exterior side and an interior side to provide said pressure interface, and moveable within said housing in a first direction to move said pressurized gas valving means from said first position to said second position.

37. The device of claim 36, wherein said pressure-responsive means further comprises:

means for moving said pressurized gas valving means from said second position to said first position in response to a predetermined inspiratory pressure in said user'"'"'s breathing passges, the movement of said pressurized gas valving means from said second position to said first position urging said piston toward a second direction, opposite to said first direction, against a pressure on the exterior side ofsaid piston.

38. The device of claim 37, wherein said means for adjustably applying pressure comprises:

means acting on the exterior side of said piston, for adjusting said predetermined inspiratory pressure.

39. The device of claim 38, wherein said means acting on the exterior side of said piston comprises:

pressurization means, engageable with the exterior side of said piston, for adjustably biasing said piston toward said first direction, so that said predetermined inspiratory pressure which causes said pressurized gas valving means to move from said second position to said first position is adjustably varied.

40. The device of claim 39, wherein said pressurization means comprises:

first means for providing positively pressurized inhalation by engaging said piston during inhalation; and

second means for maintaining a predetermined positive pressure in said user'"'"'s breathing passage at the end of exhalation, so that positive end expiratory pressure is provided.

41. the device of claim 40, wherein said first and second means are independently operable.

42. The device of claim 38, wherein said pressure adjustment means increases said predetermined inspiratory pressure relative to ambient pressure in response to decreasing ambient pressure on the exterior of said housing.

43. The device of claim 42, wherein said pressure-adjustment means comprises:

first expandable means for expanding in response to said user'"'"'s inhalation;

second expandable means for gradually expanding in response to decreasing ambient pressure on the exterior of said housing; and

said first and second expandable means and said piston being arranged so that the expansion of said first and second expandable means increasingly pressurizes the exterior side of said piston in proportion to the decrease in ambient pressure on the exterior of said housing, to maintain a substantially constant absolute pressure on the exterior side of said piston, so that said predetermined inspiratory pressure which causes said pressurized gas valving means to move from said second position to said first position is increased relative to decreasing ambient pressure.

44. The device of claim 36, wherein said exhalation outlet is provided through said piston, and said pressure-responsive means comprises:

exhalation valving means for opening said exhalation outlet only when said pressurized gas valving means is in said first position.

45. The device of claim 36, further comprising:

substantially frictionless sealing means between said piston and said housing.

46. The device of claim 35, wherein said pressure-responsive means comprises:

aperture means through said pressure interface; and

means for closing said aperture means during inhalation and opening said aperture means in response to said user'"'"'s exhalation to provide said exhalation outlet.

47. The device of claim 35, wherein said pressurized gas valving means comprises:

a main valving means for opening and closing said pressurized gas outlet means; and

pilot valving means for actuating said main valving means against the force exerted by said pressurized gas.

48. The device of claim 47, wherein said pressure-responsive means is rigidly linked to said pilot valving means, and said pressure-responsive means is moveable in a first direction in response to inhalation to open said pilot valving means, thereby opening said main valving means.

49. The device of claim 47, wherein said main valving means comprises:

a slidable member in said valve body and having first and second surfaces, said member being slidable in a first direction to open said pressurized gas outlet means when the force exerted by said pressurized gas on said first surface exceeds the force exerted by said pressurized gas on said second surface, the opening of said pressurized gas outlet means tending to cause a sudden decrease in the gas pressure proximate said first surface, resulting in a corresponding decrease in the force exerted by said pressurized gas against said first surface; and

means, proximate said first surface, for recovering at least part of the gas pressure proximate said first surface to maintain a force against said first surface as said pressurized gas outlet means is opened so that the chattering of said main valving means is substantially prevented.

50. The device of claim 35, further comprising:

an air inlet into said housing; and

automatic valving means for closing said inlet when said pressurized gas in said pressurized gas inlet means is at or above a first predetermined pressure, and opening said air inlet (a) when the pressure of said pressurized gas in said inlet means is below said first predetermined pressure, and (b) when the pressure in said housing is above a second predetermined pressure.

51. The device of claim 35, wherein said valve body outlet means provides a jet nozzle effect to reduce inhalation effort.

52. A device for regulating the flow of a pressurized fluid, comprising:

a housing having a passage means for conducting said pressurized fluid to a point of use;

a valve body in said housing, said valve body having an inlet and an outlet for said pressurized fluid, said inlet adapted to be connected to a pressurized fluid source, said outlet communicating with said passage means in said housing;

main valving means in said valve body for opening and closing said outlet, said valving means having two opposed sides, the pressure of said pressurized fluid tending to maintain a greater fluid pressure force on one side of said main valving means than the fluid pressure force on the other side thereof to maintain said main valving means in a first position which closes said outlet;

linearly movable pilot valving means for controllably venting the pressure which maintains said main valving means in said first position, so that said main valving means moves to a second position which opens said outlet; and

pressure-responsive means, including a pressure interface between the interior and exterior of said housing for both (a) actuating said pilot valving means when the pressure on the interior side of said pressure interface is less than the pressure on the exterior by a predetermined amount and (b) providing exhaust outlet means for said fluid to exit said housing when said main valving means is in said first position.

53. The device of claim 52, wherein said pressure-responsive means comprises:

a piston having an exterior side and an interior side to provide said pressure interface, said piston being connected to said pilot valving means and moveable within said housing in a first direction to open said pilot valving means.

54. The device of claim 53, wherein said pressure-responsive means further comprises:

means for closing said pilot valving means in response to a predetermined increase in pressure in said housing, said main valving means moving from said second position to said first position to close said pressurized fluid outlet in response to the closing of said pilot valving means, the closing of said pilot valving means urging said piston toward a second direction opposite to said first direction, against a pressure on the exterior side of said piston.

55. The device of claim 54, further comprising:

pressure adjustment means, acting on the exterior side of said piston, for adjusting said predetermined increase in pressure which actuates said pilot valve closing means.

56. The device of claim 55, wherein said pressure-adjustment means comprises:

pressurization means, engageable with the exterior side of said piston, for adjustably biasing said piston toward said first direction, so that said predetermined increase in pressure which actuates said pilot valve is adjustably varied.

57. The device of claim 56, wherein said pressurized fluid is a breathable gas, said housing includes passage means for communication with a user'"'"'s breathing passages, and said pressurization means comprises:

breathing pressure control means for adjustably controlling said user'"'"'s inhalation effort and exhalation effort.

58. The device of claim 57, wherein said breathing pressure control means comprises:

first means for controlling inspiratory pressure by biasing said piston in said first direction during inhalation; and

second means for adjustably maintaining a positive end expiratory pressure in said user'"'"'s breathing passages by biasing said piston in said first direction at the end of exhalation.

59. The device of claim 58, wherein said first and second means are independently operable.

60. The device of claim 59, further comprising:

said first expandable means for actuating said first means by expanding to engage said first means;

first valving means for admitting said breathable gas into said first expandable means to effect the expansion thereof, and for venting said gas from said first expandable means;

timing means for actuating said first valving means to admit said gas to said first expandable means at a selected time interval;

first control means, responsive to said user'"'"'s inspiratory pressure, for actuating said first valving means to vent said gas from said first expandable means when a predetermined inspiratory pressure is reached;

second expandable means for actuating said second means by expanding to engage said second means;

second valving means for admitting said breathable gas into said second expandable means to effect the expansion thereof, and for venting said gas from said second expandable means; and

second control means responsive to said inspiratory pressure, for actuating said second valving means to alternately admit and vent said gas in a selectable sequence, said sequence initiated in response to a predetermined rise in said inspiratory pressure.

61. The device of claim 57, wherein said pressurization means comprises:

expandable means, engaging the exterior side of said piston, for expanding in response to decreasing ambient pressure on the exterior side of said piston, said expansion and said decreasing ambient pressure maintaining a substantially constant total pressure on the exterior side of said piston to bias said piston in said first direction with substantially constant pressure as said ambient pressure decreases, so that said predetermined increase in pressure which actuates said pilot valve is correspondingly increased relative to decreasing ambient pressure.

62. The device of claim 53, wherein said exhaust outlet means is provided through said piston, and said pressure-responsive means comprises:

said exhaust outlet valving means opening said exhaust outlet means only when said pilot valving means is closed.

63. The device of claim 53, further comprising:

sealing means for providing a substantially frictionless seal between said piston and said housing.

64. The device of claim 63, wherein said sealing means comprises:

a groove around the periphery of said piston; and

an "O" ring of generally circular cross-section in said groove having a thickness less than both the depth and the width of said groove and a diameter slightly larger than the inside diameter of said housing around said piston to permit limited free movement of said piston.

65. The device of claim 63, wherein said sealing means comprises:

a sealing member mounted on said housing, sealingly engaging said piston at the extremes of its movement within said housing, but disengaging said piston during said movement.

66. The device of claim 53, wherein the movement of said piston in said first direction actuates said pilot valving means by straight line motion.

67. The device of claim 52, wherein said exhaust outlet means from said housing comprises:

means forming an aperture through said pressure interface; and

means for closing said aperture when the pressure on the interior side of said interface is less than or equal to the pressure on the exterior side of said interface, and opening said aperture when the pressure on the interior side of said interface exceeds the pressure on the exterior side.

68. the device of claim 52, further comprising:

means engageable against the exterior side of said pressure interface for adjustably increasing the pressure on said exterior side.

69. The device of claim 52, wherein said main valving means comprises:

a slidable member in said valve body and having first and second surfaces, the area of said second surface being greater than the area of said first surface, said member being slidable in a first direction to open said pressurized fluid outlet when the force exerted by said pressurized fluid on said first surface exceeds the force exerted by said pressurized fluid on said second surface, the opening of said pressurized fluid outlet tending to depressurize the area proximate said first surface resulting in a corresponding decrease in the force exerted on said first surface; and

means proximate said first surface, for providing at least a partial fluid pressure recovery in said area proximate said first surface as said pressurized fluid outlet is opened to maintain a force against said first surface, so that said main valving means is substantially prevented from chattering.

70. A breathing regulator comprising:

a valve body having inlet means for communicating with a source of pressurized breathable gas, and gas outlet means for communicating with the breathing passages of an animal;

main valving means in said valve body for opening and closing said outlet means, said valving means, when closed, having a pair of unequal sized opposing surfaces subject to the pressure of said pressurized breathable gas to bias said valving means to a closed position;

pilot valving means for controllably actuating said main valving means against the pressure exerted by said pressurized gas; and

a piston rigidly attached to said pilot valving means for actuating said pilot valving means in response to a predetermined, breathing induced change in pressure in said outlet means.

71. A breathing regulator, comprising:

a valve body having inlet means for communicating with a source of pressurized breathable gas, and outlet means for said gas, said outlet means being fluidly connectable with the breathing passages of an animal;

main valving means, in said valve body, for opening and closing said outlet means;

a pilot valve chamber communicating with said main valving means, the pressure in said chamber controlling said opening and closing of said outlet means by said main valving means;

a pilot orifice in said pilot valve chamber for exhausting said chamber;

slideably movable pilot orifice closing means for controllably exhausting said chamber; and

linearly moveable, pressure-responsive means for actuating said orifice closing means in response to a predetermined change in pressure in said outlet means, said change in pressure being induced by said animal'"'"'s breathing.

72. A device for the regulation of a user'"'"'s breathing from a source of pressurized gas, comprising:

a valve body having inlet and outlet means for said pressurized gas;

an outlet chamber for communicating with said outlet means and said user'"'"'s breathing passages;

valving means in said valve body for controllably opening and closing said outlet means in response to said user'"'"'s inspiratory and expiratory pressures;

said inspiratory and expiratory pressures being determined by a pressure differential induced between the interior and exterior of said outlet chamber during inhalation and exhalation, respectively; and

means forming a pressure-responsive interface between the interior and exterior of said outlet chamber for controllably varying both said inspiratory and expiratory pressures by controllably adjusting said pressure differential.

73. The device of claim 72, further comprising:

means for substantially preventing damage to said user'"'"'s lungs resulting from an explosive decompression of said user'"'"'s environment.

74. A device for the regulation of a user'"'"'s breathing from a source of pressurized gas, comprising:

a valve body having pressurized gas inlet means and gas outlet means communicating with said user'"'"'s breathing passages;

valving means in said valve body for controllably opening said outlet means in response to said user'"'"'s inhalation and closing said outlet means when a predetermined absolute inspiratory pressure is reached in said user'"'"'s breathing passages and communicated to said gas outlet means, said predetermined absolute inspiratory pressure tending to remain constant with decreasing external ambient pressure; and

means, responsive to the pressure at said gas outlet means and the external ambient pressure, for maintaining said predetermined inspiratory pressure as said ambient pressure decreases.