Oxygen-conserving regulator assembly

• US 6,116,242 A
• Filed: 04/28/1997
• Issued: 09/12/2000
• Est. Priority Date: 09/28/1995
• Status: Expired due to Fees

• Current Assignee: Caire Incorporated (Niterra Co., Ltd.)
• Original Assignee: Nellcor Puritan Bennett Incorporated (Medtronic Plc)
• Inventors: Davis, Richard A., Grenaway, John R., Leithauser, Douglas R., Frye, Mark R.
• Primary Examiner(s): Weiss, John G.
• Assistant Examiner(s): ANDERSON, CHARLES WENDELL
• Application Number:
  US08/849,417
• Time in Patent Office: 1,233 Days
• Field of Search: 128/205.24, 128/204.18, 128/204.23, 128/207.12, 128/204.26, 128/204.28
• US Class Current: 128/205.24
• 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: A61M 16/0677 Gas-saving devices therefor
• CPC Class Codes: A61M 16/0841 for sampling
• 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 16/207 Membrane valves with pneumatic amplification stage, i.e. having master and slave membranes
• CPC Class Codes: A61M 2016/0021 with a proportional output signal, e.g. from a thermistor
• CPC Class Codes: A61M 2202/0007 introduced into the body
• CPC Class Codes: A61M 2202/0208 Oxygen
• CPC Class Codes: A61M 2202/03 Gases in liquid phase, e.g. cryogenic liquids
• CPC Class Codes: A61M 2205/8225 using incorporated gas cartridges for the driving gas

Abstract

An apparatus is provided for controlling discharge of oxygen from an oxygen supply source to a patient. The apparatus includes an oxygen supply inlet, a pressure regulator coupled to the oxygen supply inlet and configured to reduce pressure of oxygen received from the oxygen supply inlet to a selected magnitude, a flow controller coupled to the pressure regulator and configured to meter oxygen received from the pressure regulator at a selected flow rate, and an oxygen distribution assembly including a pneumatic demand oxygen valve and a conduit conducting oxygen discharged from the flow controller through the pressure regulator to the pneumatic demand oxygen valve for delivery to a patient. The flow controller includes a chamber and a rotary valve for splitting oxygen discharged from the chamber into a first stream in an oxygen supply passageway for use by a patient and a second stream in a diaphragm supply passageway for controlling operation of pneumatic demand oxygen valve.

Claims

1. Apparatus for controlling discharge of oxygen from an oxygen supply source to a patient, the apparatus comprising

an oxygen supply inlet,

a pressure regulator coupled to the oxygen supply inlet and configured to reduce pressure of oxygen received from the oxygen supply inlet to a selected magnitude,

a flow controller coupled to the pressure regulator to position the pressure regulator between the oxygen supply inlet and the flow controller and configured to meter oxygen received from the pressure regulator at a selected flow rate, and

an oxygen distribution assembly including a pneumatic demand oxygen valve and a conduit conducting oxygen discharged from the flow controller to the pneumatic demand oxygen valve for delivery to a patient, the pressure regulator being positioned to lie between the flow controller and the pneumatic demand oxygen valve.

2. The apparatus of claim 1, wherein the pressure regulator includes a regulator body and a regulator mechanism positioned to lie in the regulator body and receive oxygen from the oxygen supply inlet and the regulator body is formed to include a portion of the conduit so the oxygen discharged from the flow controller passes through the regulator body before said oxygen is admitted into the pneumatic demand oxygen valve.

3. The apparatus of claim 2, wherein the pneumatic demand oxygen valve includes a valve body formed to include a patient supply passageway having a gas inlet coupled to the conduit and a gas outlet for attachment to a breathing line and a diaphragm valve member movable to open and close the patient supply passageway and the oxygen distribution assembly further includes an auxiliary conduit conducting oxygen from the flow controller to the diaphragm valve member to move the diaphragm valve member to a position closing the patient supply passageway.

4. The apparatus of claim 3, wherein the regulator body is formed to include a portion of the auxiliary conduit.

5. The apparatus of claim 3, wherein the flow controller includes a flow controller housing formed to include an internal chamber coupled to the conduit and to the auxiliary conduit, a passageway conducting oxygen from the pressure regulator to the internal chamber, and a flow control valve positioned in the internal chamber for movement relative to the flow controller housing between a first position range communicating oxygen from the internal chamber though the conduit and the auxiliary conduit to the diaphragm valve member, a second position range communicating oxygen from the internal chamber though the conduit to the diaphragm valve member without flowing oxygen through the auxiliary conduit to the diaphragm valve member, and a third position range blocking flow of oxygen in the internal chamber to the diaphragm valve member through the conduit and the auxiliary conduit.

6. The apparatus of claim 3, wherein the flow controller includes a flow controller housing coupled to the regulator body and formed to include an internal chamber coupled to the conduit and a flow control valve positioned in the internal chamber for movement relative to the housing to control discharge of oxygen from the internal chamber into the conduit and the pneumatic demand oxygen valve includes a valve body coupled to the regulator body and formed to include a patient supply passageway having a gas inlet coupled to the conduit and a gas outlet for attachment to a breathing line and a valve member movable relative to the valve body to open and close the patient supply passageway.

7. The apparatus of claim 6, wherein the regulator body includes a first external surface facing in one direction and a second external surface facing in another direction, the flow controller housing is coupled to the first external surface, and the valve body is coupled to the second external surface.

8. The apparatus of claim 1, wherein the conduit includes an inlet end coupled to the flow controller, an outlet end coupled to the pneumatic demand oxygen valve, and a middle portion interconnecting the inlet and outlet ends and passing through the regulator body of the pressure regulator.

9. The apparatus of claim 1, wherein the pressure regulator includes a regulator body receiving oxygen from the oxygen supply inlet and a regulator mechanism regulating pressure of oxygen received in the regulator body and the pneumatic demand oxygen valve includes a valve body coupled to the regulator body and formed to include a patient supply passageway having a gas inlet for attachment to the conduit and a gas outlet adapted for attachment to a breathing line and a valve seat in the patient supply passageway and a valve member for engaging and disengaging the valve seat to control flow of gas inlet to the gas outlet through the patient supply passageway.

10. The apparatus of claim 9, wherein the regulator body is formed to include a portion of the conduit.

11. The apparatus of claim 10, wherein the valve member includes a first wall facing away from the valve seat and a second wall facing toward the valve seat, the oxygen distribution assembly further includes an auxiliary conduit conducting oxygen from the flow controller to the first wall of the valve member, the valve body is formed to cause the patient supply passageway to conduct oxygen to the second wall of the valve member, and the regulator body is also formed to include a portion of the auxiliary conduit.

12. The apparatus of claim 9, wherein the pneumatic demand oxygen valve further includes a differential pressure controller positioned to lie in the valve body and configured to communicate with the auxiliary conduit and move the valve member from a closed position against the valve seat to an opened position away from the valve seat in response to inhalation of a patient breathing through the gas outlet.

13. The apparatus of claim 9, wherein the flow controller includes means for splitting the flow of oxygen received from the pressure regulator into a first oxygen stream discharged into the conduit and conducted through the patient supply passageway to reach a first side of the valve member facing toward the valve seat and a second oxygen stream conducted through an auxiliary conduit formed in the regulator body to reach a second side of the valve member facing away from the valve seat.

14. The apparatus of claim 1, wherein the flow controller includes a housing formed to include an internal chamber coupled to the conduit and a passageway conducting oxygen from the pressure regulator to the internal chamber and a flow control valve extending into the internal chamber and moving therein to regulate oxygen flow from the internal chamber into the conduit.

15. The apparatus of claim 14, wherein the flow control valve includes a rotor disk positioned in the internal chamber to receive oxygen discharged into the internal chamber through the passageway formed in the pressure regulator and a shaft mounted in the housing to support the rotor disk for rotational movement in the internal chamber about an axis of rotation.

16. The apparatus of claim 15, wherein the rotor disk includes a plurality of oxygen flow-metering apertures conducting oxygen from the internal chamber into the conduit at selected flow rates and at selected rotated positions of the rotor disk around the axis of rotation relative to the housing.

17. The apparatus of claim 1, wherein the oxygen distribution assembly further includes an auxiliary conduit, the pneumatic demand oxygen valve includes valve means for controlling flow of oxygen from the conduit to the patient and an inhale/exhale sensing diaphragm pneumatically coupled to the valve means, the valve means is fluidly coupled to the auxiliary conduit, the flow controller includes a housing formed to include an internal chamber and a passageway conducting oxygen from the pressure regulator to the internal chamber and a flow control valve extending into the internal chamber, and the flow control valve is formed to include an oxygen flow channel to conduct oxygen from the internal chamber into the auxiliary conduit upon movement of the flow control valve to a predetermined position in the internal chamber communicating the auxiliary conduit to the oxygen flow channel so that oxygen is communicated through the auxiliary conduit to the valve means.

18. The apparatus of claim 17, wherein the pressure regulator includes a regulator body formed to include a portion of the auxiliary conduit.

19. The apparatus of claim 18, wherein the pressure regulator includes a regulator body formed to include a portion of the conduit.

20. The apparatus of claim 17, wherein the flow control valve is also formed to include a flat wall portion to block oxygen from flowing from the internal chamber into the auxiliary conduit upon movement of the valve to another predetermined position in the internal chamber.

21. The apparatus of claim 17, wherein the flow control valve includes a rotor disk and a shaft supporting the rotor disk for rotational movement in the internal chamber about an axis of rotation and the oxygen flow channel has an arcuate shape.

22. The apparatus of claim 21, wherein the rotor disk further includes a plurality of oxygen flow-metering apertures surrounding the arcuate oxygen flow channel.

23. The apparatus of claim 21, wherein the flow controller further includes a flow selector knob coupled to the shaft and supported to rotate about the axis of rotation relative to the housing between a first position range placing the oxygen flow channel in communication with the auxiliary conduit to allow oxygen to flow from the internal chamber into the auxiliary conduit to reach the valve means in the pneumatic demand oxygen valve and a second position range placing flat wall portion in communication with the auxiliary conduit to block oxygen from flowing from the internal chamber into the auxiliary conduit toward the valve means.

24. Apparatus for controlling discharge of oxygen from an oxygen supply source to a patient, the apparatus comprising

an oxygen supply inlet,

a pressure regulator coupled to the oxygen supply inlet and configured to reduce pressure of oxygen received from the oxygen supply inlet to a selected magnitude,

a flow controller coupled to the pressure regulator and configured to meter oxygen received from the pressure regulator at a selected flow rate,

an oxygen distribution assembly including a pneumatic demand oxygen valve and a conduit conducting oxygen discharged from the flow controller to the pneumatic demand oxygen valve for delivery to a patient, the pressure regulator being positioned to lie between the flow controller and the pneumatic demand oxygen valve,

first detachable connector means for detachably connecting the flow controller to the pressure regulator, and

second detachable connector means for detachably connecting the pneumatic demand oxygen valve to the pressure regulator.

25. The apparatus of claim 24, wherein the pressure regulator includes a modular regulator body, the flow controller includes a modular flow controller housing, the pneumatic demand oxygen valve includes a modular valve body, the first detachable connector means includes at least one fastener coupling the modular flow controller housing to one side of the modular regulator body, and the second detachable connector means includes at least one fastener coupling the modular flow controller housing to another side of the modular regulator body.

26. The apparatus of claim 25, wherein the modular flow controller housing includes a mounting orientation post, the modular valve body includes a mounting orientation post, the one side of the modular regulator body is formed to include an aperture receiving the mounting orientation post of the modular flow controller housing, and the another side of the modular regulator body is formed to include an aperture receiving the mounting orientation post of the modular valve body.

27. The apparatus of claim 25, wherein the one side of the modular regulator body faces in a first direction and the another side of the modular regulator body faces in a second direction opposite to the first direction.

28. Apparatus for controlling discharge of oxygen from an oxygen supply source to a patient, the apparatus comprising

an oxygen supply inlet,

a modular pressure regulator coupled to the oxygen supply inlet and configured to reduce pressure of oxygen received from the oxygen supply inlet to a selected magnitude,

a modular flow controller configured to meter oxygen received from the pressure regulator at a selected flow rate,

a first connector coupled to the modular pressure regulator and to the modular flow controller to position the modular pressure regulator adjacent to the modular flow controller and to communicate oxygen from the modular pressure regulator to the modular flow controller,

an oxygen distribution assembly including a modular pneumatic demand oxygen valve and a conduit conducting oxygen discharged from the modular flow controller to the modular pneumatic demand oxygen valve for delivery to a patient, and

a second connector coupled to the modular pressure regulator and the modular pneumatic demand oxygen valve to position the modular pneumatic demand oxygen valve adjacent to the modular pressure regulator.

29. The apparatus of claim 28, wherein the modular flow controller includes a mounting orientation post, the modular pneumatic demand valve includes a mounting orientation post, and the modular pressure regulator is formed to include a first aperture receiving the mounting orientation post of the modular flow controller and a second aperture receiving the mounting orientation post of the modular pneumatic demand valve.

30. The apparatus of claim 29, wherein the modular pressure regulator includes a first side wall formed to include the first aperture and a second side wall formed to include the second aperture.

31. The apparatus of claim 30, wherein the first side wall faces in a first direction and the second side wall faces in a second direction opposite to the first direction.

32. The apparatus of claim 29, wherein the mounting orientation post of the modular flow controller is positioned to lie in spaced-apart relation to the first connector and the mounting orientation post is configured to lie in spaced-apart relation to the second connector.

33. The apparatus of claim 28, wherein the modular pressure regulator and the modular flow controller are positioned to lie in side-by-side relation.

34. The apparatus of claim 32, wherein the modular pressure regulator abuts the modular flow controller.

35. The apparatus of claim 28, wherein the modular pressure regulator and the modular pneumatic demand oxygen valve are positioned to lie in side-by-side relation.

36. The apparatus of claim 35, wherein the modular pressure regulator abuts the modular flow controller.

37. The apparatus of claim 28, wherein the conduit includes an inlet end coupled to the modular flow controller, an outlet end coupled to the modular pneumatic demand oxygen valve, and a middle portion interconnecting the inlet and outlet ends and passing through the modular pressure regulator.

38. The apparatus of claim 37, wherein the oxygen distribution assembly further includes an auxiliary conduit conducting oxygen from the modular flow controller to a valve member mounted in a space formed in the modular pneumatic demand valve in communication with the conduit to control oxygen flow from the conduit to a patient through the modular pneumatic demand valve, the modular pressure regulator is formed to include a portion of the pressure regulator.

39. The apparatus of claim 28, wherein the oxygen distribution assembly further includes an auxiliary conduit conducting oxygen from the modular flow controller to a valve member mounted in a space formed in the modular pneumatic demand valve in communication with the conduit to control oxygen flow from the conduit to a patient through the modular pneumatic demand valve, the modular pressure regulator is formed to include a portion of the pressure regulator.

40. The apparatus of claim 28, wherein the modular pneumatic demand valve includes a diaphragm valve member communicating with the conduit and an inhale/exhale sensing diaphragm pneumatically coupled to the diaphragm valve member and the modular flow controller includes an internal chamber and means for splitting the flow of oxygen received in the internal chamber from the modular pressure regulator into a first oxygen stream discharged into the conduit and a second oxygen stream, and the apparatus further comprises means for selectively communicating the second oxygen stream to the diaphragm valve member in the modular pneumatic demand valve.

41. An apparatus for controlling discharge of oxygen from an oxygen supply source to a patient through a breathing line coupled to the patient as the patient inhales and exhales, the apparatus comprising

an oxygen supply inlet,

a modular pressure regulator coupled to the oxygen supply inlet and configured to reduce pressure of oxygen received from the oxygen supply inlet to a selected magnitude,

a modular flow controller configured to meter oxygen received from the pressure regulator at a selected flow rate,

means for conducting oxygen provided by the modular flow controller through a supply passageway having a gas inlet coupled to the modular flow controller and a gas outlet for attachment to a breathing line, the conducting means including a valve seat in the supply passageway,

means for storing a supply of oxygen extant in the supply passageway in a first chamber to develop a pressure head in the first chamber, the storing means including auxiliary conduit means for admitting oxygen from the modular flow controller into the first chamber and outlet means for discharging oxygen from the first chamber to the atmosphere,

means for selectively blocking flow of oxygen through the supply passageway from the gas inlet to the gas outlet, the blocking means including a flexible diaphragm valve member including a first side communicating with oxygen admitted into the first chamber and a second side facing the valve seat in the supply passageway, the diaphragm valve member being mounted for movement between a flow-blocking position engaging the valve seat in the supply passageway and a flow-delivery position disengaging the valve seat in the supply passageway, and

control means for closing the outlet means during exhalation of a patient breathing thorough the gas outlet to store pressurized oxygen in the first chamber so that oxygen pressure in the first chamber acting against the first side of the diaphragm valve member will increase to move the diaphragm valve member to its flow-blocking position and opening the outlet means in response to inhalation of a patient breathing through the gas outlet to vent pressurized oxygen in the first chamber to the atmosphere through the outlet means so that oxygen pressure in the first chamber will decrease to allow pressurized oxygen in the supply passageway to move the diaphragm valve member away from the valve seat to its flow-delivery position, the modular flow controller including an internal chamber and means for selectively splitting the flow of oxygen received in the internal chamber from the modular pressure regulator into a first oxygen stream discharged into the supply passageway for distribution to a patient and a second oxygen stream discharged into the auxiliary conduit means for distribution to the first chamber.

42. Apparatus for controlling discharge of oxygen from an oxygen supply source to a patient, the apparatus comprising

a flow controller housing formed to include a sealed internal chamber having an oxygen-receiving inlet adapted to be coupled to an oxygen supply source, a first oxygen-discharging outlet, and a second oxygen-discharging outlet, and

a flow control valve positioned in the sealed internal chamber for movement relative to the flow controller housing between a first position range discharging oxygen from the sealed internal chamber through the first oxygen-discharging outlet and through the second oxygen-discharging outlet and a second position range discharging oxygen from the sealed internal chamber through the first oxygen-discharging outlet without discharging oxygen from the sealed internal chamber through the second oxygen-discharging outlet.

43. The apparatus of claim 42, wherein the flow control valve is also positioned in the sealed internal chamber for movement relative to the flow controller housing to a third position range blocking flow of oxygen from the sealed internal chamber through the first and second oxygen-discharging outlets.

44. The apparatus of claim 43, wherein the flow control valve includes a rotor disk positioned in the sealed internal chamber to receive oxygen admitted into the

sealed internal chamber through the oxygen-receiving inlet and a shaft mounted in the housing to support the rotor disk for rotational movement in the sealed internal chamber about an axis of rotation between the first, second and third position ranges.

45. The apparatus of claim 44, wherein the rotor disk is formed to include a plurality of oxygen flow-metering apertures conducting oxygen from the sealed internal chamber to the first oxygen-discharging outlet upon movement of the flow control valve to the first position range and a flow-shut off plate positioned to lie between two of the oxygen flow-metering apertures and to block flow of oxygen from the sealed internal chamber into the first oxygen-discharging outlet upon movement of the rotor disk in the sealed internal chamber to the third position range.

46. The apparatus of claim 45, wherein the rotor disk is formed to include a C-shaped oxygen flow channel having opposite ends and a flat wall portion extending between the opposite ends of the C-shaped oxygen flow channel, the C-shaped oxygen flow channel is positioned to communicate oxygen therethrough from the sealed internal chamber to the second oxygen-discharging outlet upon movement of the flow control valve to the first position range, and the flat wall portion is positioned to block flow of oxygen from the sealed internal chamber to the second oxygen-discharging outlet upon movement of the flow control valve to one of the second and third position ranges.

47. The apparatus of claim 46, wherein the rotor disk includes a front face and an opposite rear face, the front face is formed to include the flow-shut off plate, the C-shaped oxygen flow channel, the flat wall portion, and an outlet of each of oxygen flow-metering aperture, and the rear face is formed to include an inlet of each oxygen flow-metering aperture.

48. The apparatus of claim 42, wherein the flow control valve includes a rotor disk positioned in the sealed internal chamber to receive oxygen admitted into the sealed internal chamber through the oxygen-receiving inlet and a shaft mounted in the housing to support the rotor disk for rotational movement in the sealed internal chamber about an axis of rotation between the first and second position ranges.

49. The apparatus of claim 48, wherein the rotor disk is formed to include a plurality of oxygen flow-metering apertures, each of the oxygen flow-metering apertures includes a flow restriction passage of a predetermined internal diameter, and each of the oxygen flow-metering apertures is located in the rotor disk to conduct oxygen from the sealed internal chamber to the first oxygen-discharging outlet upon rotation of the rotor disk about the axis of rotation to move the flow control valve to one of the first and second position ranges.

50. The apparatus of claim 49, wherein the rotor disk is formed to include a rear face facing in a first direction toward the shaft and a front face facing in a second direction opposite to the first direction, the rear face is formed to include an inlet opening for each oxygen flow-metering aperture receiving oxygen extant in the sealed internal chamber, and the front face is formed to include an outlet opening for each oxygen flow-metering aperture discharging oxygen into the first oxygen-discharging outlet upon movement of the flow control valve to one of the first and second position ranges.

51. The apparatus of claim 50, wherein the front face is also formed to include a C-shaped oxygen flow channel having opposite ends and a flat wall portion extending between the opposite ends of the C-shaped oxygen flow channel, the C-shaped oxygen flow channel is positioned to communicate oxygen therethrough from the sealed internal chamber to the second oxygen-discharging outlet upon movement of the flow control valve to the first position range, and the flat wall portion is positioned to block flow of oxygen from the sealed internal chamber to the second oxygen-discharging outlet upon movement of the flow control valve to the second position range.

52. A flow controller for use in an apparatus for controlling discharge of oxygen from an oxygen supply source to a patient, the flow controller comprising

a modular housing formed to include a sealed internal chamber, an inlet conduit adapted to be coupled to an oxygen supply source and configured to conduct oxygen from the oxygen supply source into the sealed internal chamber, a first outlet positioned to conduct a first stream of oxygen discharged from the sealed internal chamber toward a first point of use, and a second outlet positioned to conduct a second stream of oxygen discharged from the sealed internal chamber toward a second point of use,

a valve positioned to lie in the sealed internal chamber formed in the modular housing for movement from a first position range placing the inlet conduit in fluid communication with both of the first and second outlets so that oxygen flowing into the sealed internal chamber is split to cause the first stream to flow out of the sealed internal chamber through the first outlet and the second stream to flow out of the sealed internal chamber through the second outlet to a second position range placing the inlet conduit in fluid communication only with the first outlet so that oxygen flowing into the sealed internal chamber is discharged through the first outlet without flowing through the second outlet, and

a valve controller coupled to the modular housing to move the valve in the sealed internal chamber between the first and second position ranges.

53. The flow controller of claim 52, wherein the valve controller includes a shaft coupled to the modular housing for rotation about an axis and the shaft includes an inner end coupled to the valve to support the valve for rotation about the axis during movement of the valve between the first position range and the second position range.

54. The flow controller of claim 53, wherein the shaft includes an outer end and the flow controller further includes a flow selector knob coupled to the outer end of the shaft and configured to be gripped by a user to rotate the shaft and the valve about the axis to position the valve in one of the first and second position ranges.

55. The flow controller of claim 54, wherein the modular housing includes a mounting plate and an interface plate coupled to the mounting plate to define the sealed internal chamber therebetween, the interface plate is positioned to lie between the mounting plate and the flow selector knob and is configured to support the shaft for rotation about the axis, and the mounting plate is formed to include the inlet conduit and the first and second outlets.

56. The flow controller of claim 54, further comprising a detent mechanism mounted in the modular housing in spaced-apart relation to the shaft to fix the position of the rotatable valve in one of several predetermined fixed positions within the modular housing to retain the valve in a selected one of the first and second position ranges.

57. The flow controller of claim 53, wherein the valve includes a rear face coupled to the shaft and a front face arranged to face away from the shaft, the valve is formed to include a plurality of oxygen flow-metering apertures situated to lie in fluid communication with the inlet conduit and the first outlet when the valve lies in the first and second position ranges, and each flow-metering aperture is defined by an inlet formed in the rear face, an outlet formed in the front face, and a flow-restriction passage interconnecting an inlet and a companion outlet.

58. The flow controller of claim 57, wherein the front face of the valve is formed to include a C-shaped oxygen flow channel having opposite ends and a flat wall portion extending between the opposite ends of the C-shaped flow channel, the C-shaped flow channel is positioned to communicate oxygen therethrough from the sealed internal chamber to the second outlet upon movement of the valve to the first position range, and the flat wall portion is positioned to block flow of oxygen from the sealed internal chamber to the second outlet upon movement of the valve to the second position range.

59. The flow controller of claim 53, wherein the valve includes a rear face coupled to the shaft and a front face arranged to face away from the shaft and the valve is formed to include a plurality of oxygen flow-metering apertures having openings in the front and rear faces and a C-shaped oxygen flow channel formed in the front face to communicate oxygen therethrough from the sealed internal chamber to the second outlet only upon movement of the valve to the first position range.

60. The flow controller of claim 59, wherein the front face of the valve is formed to include a ring of openings into the oxygen flow-metering apertures surrounding the C-shaped oxygen flow channel.

61. The flow controller of claim 59, further comprising a detent mechanism mounted in the modular housing in spaced-apart relation to the shaft to fix the position of the rotatable valve in one of several predetermined fixed positions within the modular housing to retain the valve in a selected one of the first and second position ranges, the rear face of the valve is formed to include an outer ring of openings into the oxygen flow-metering apertures, and the rear face of the valve is also formed to include an inner ring of circumferentially spaced-apart depressions configured to receive the detent mechanism therein.

62. The flow controller of claim 52, wherein the modular housing includes a mounting plate formed to include the inlet conduit and the first and second outlets, a first O-ring seal stack mounted in the first outlet to support and sealingly engage the valve, and a second O-ring seal stack mounted in the second outlet to support and sealingly engage the valve.

63. The flow controller of claim 62, wherein the valve includes a rear face coupled to the valve controller and a front face sealingly engaging the first and second O-ring stacks during movement of the valve in the sealed internal chamber and when the valve is stationary.

64. The flow controller of claim 63, wherein the valve controller includes a shaft coupled to the modular housing for rotation about an axis and the shaft includes an inner end coupled to the rear face to support the valve for rotation about the axis and sealing engagement with the first and second O-ring seal stacks.

65. The flow controller of claim 63, wherein the valve is formed to include a plurality of oxygen flow-metering apertures having openings in the front and rear faces and being positioned to communicate oxygen therethrough from the sealed interior chamber through an oxygen-conducting passage defined by the first O-ring seal stack in the first outlet when the valve lies in the first and second position ranges and a C-shaped oxygen flow channel formed in the front face to communicate oxygen therethrough from the sealed interior chamber through an oxygen-conducting passage defined by the second O-ring seal stack in the second outlet only upon movement of the valve to the first position range.