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A pneumatic oxygen conserving device includes a reservoir of pressurized gas delivered upon inhalation through a single-lumen cannula. Gas flow is interrupted by a series of interconnected passages and chambers, including a check valve which is acted upon by the flow of gas being delivered through t

A pneumatic oxygen conserving device includes a reservoir of pressurized gas delivered upon inhalation through a single-lumen cannula. Gas flow is interrupted by a series of interconnected passages and chambers, including a check valve which is acted upon by the flow of gas being delivered through the delivery outlet of the device. The device is self regulating to the extent that oxygen pulses of appropriate volume are delivered irrespective of the breathing rate of the user. The device includes a plate with various passages and chambers defined therein in such a way as to reduce the overall length of the device.

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1. A conserving device for use in delivering gas from a source of gas through a gas line to a patient, the conserving device comprising:a reservoir having an inlet for receiving the gas into the reservoir and an outlet for discharging the gas from the reservoir;a main valve in pneumatic communicatio

1. A conserving device for use in delivering gas from a source of gas through a gas line to a patient, the conserving device comprising:a reservoir having an inlet for receiving the gas into the reservoir and an outlet for discharging the gas from the reservoir;a main valve in pneumatic communication with the outlet of the reservoir and operable between a closed position for closing the outlet to pressurize the reservoir and an open position for opening the outlet to depressurize the reservoir;a pressure line extending pneumatically and communicating between the source of the gas and the main valve to bias the main valve towards the closed position, the pressure line terminating in a port;a sensing valve in pneumatic communication with the port and operable between a closed position to close the port and an open position to open the port and allow the gas from the pressure line to flow therethrough;a delivery outlet in pneumatic communication with the outlet of the reservoir and the gas line to deliver the gas discharged from the reservoir;a sensing passage communicating between the delivery outlet and the sensing valve;wherein, in response to inhalation by the patient through the gas line connected to the delivery outlet, air is drawn through the sensing passage and from the sensing valve to move the sensing valve to the open position to open the port, whereupon the biasing of the main valve is sufficiently reduced for the main valve to move to the open position, whereupon the outlet to the reservoir is opened and the gas therein is discharged from and exits through the delivery outlet to the patient; andwherein the sensing passage is disposed relative to the delivery outlet so that a portion of the gas flowing into the delivery outlet passes through the sensing passage to bias the sensing valve toward the closed position, the sensing valve closing the port when predetermined pressures are achieved in the sensing valve, whereupon the gas from the pressure line moves the main valve to close the reservoir outlet, interrupting delivery of the gas to the patient and permitting repressurizing of the reservoir, whereby the gas is delivered intermittently and is conserved. 2. The device of claim 1, further comprising a vent in pneumatic communication with the port to allow gas flowing from the port to escape to the ambient. 3. The device of claim 1 further comprising a plurality of orifices disposed in spaced relation on an orifice plate, a selected one of the orifices positioned between and in pneumatic communication with the source of the gas and the inlet of the reservoir, the selected orifice corresponding to the flow of gas. 4. The device of claim 3 further comprising a pressure regulator, the pressure regulator includinga regulator inlet adapted to attach to the source of gas;means for reducing the pressure of the source of gas to a delivery pressure, anda regulator outlet for delivering the gas at the delivery pressure, the regulator outlet in pneumatic communication with the selected orifice of the orifice plate. 5. The device of claim 1, wherein the main valve comprises a chamber and an element received in the chamber and movable therein to cause the main valve to close and open when predetermined pressures exist within the chamber. 6. A conserving device for use in delivering gas from a source of gas through a gas line to a patient, the conserving device comprising:a reservoir having an inlet for receiving the gas into the reservoir and an outlet for discharging the gas from the reservoir;a main valve in pneumatic communication with the outlet of the reservoir and operable between a closed position for closing the outlet to pressurize the reservoir and an open position for opening the outlet to depressurize the reservoir;a pressure line extending pneumatically and communicating between the source of the gas and the main valve to bias the main valve towards the closed position, the pressure line terminating in a port;a sen sing valve in pneumatic communication with the port and operable between a closed position to close the port and an open position to open the port and allow the gas from the pressure line to flow therethrough;a delivery outlet in pneumatic communication with the outlet of the reservoir and the gas line to deliver the gas discharged from the reservoir;a sensing passage communicating between the delivery outlet and the sensing valve; anda vent in pneumatic communication with the port to allow gas flowing from the port to escape to the ambient;wherein the vent comprises one of a plurality of selectable orifices corresponding to a range of rates of intermittent flow of the gas;wherein, in response to inhalation by the patient through the gas line connected to the delivery outlet, air is drawn through the sensing passage and from the sensing valve to move the sensing valve to the open position to open the port, whereupon the biasing of the main valve is sufficiently reduced for the main valve to move to the open position, whereupon the outlet to the reservoir is opened and the gas therein is discharged from and exits through the delivery outlet to the patient; andwherein the sensing passage is disposed relative to the delivery outlet so that a portion of the gas flowing into the delivery outlet passes through the sensing passage to bias the sensing valve toward the closed position, the sensing valve closing the port when predetermined pressures are achieved in the sensing valve, whereupon the gas from the pressure line moves the main valve to close the reservoir outlet, interrupting delivery of the gas to the patient and permitting repressurizing of the reservoir, whereby the gas is delivered intermittently and is conserved. 7. A conserving device for use in delivering gas from a source of gas through a gas line to a patient, the conserving device comprising:a reservoir having an inlet for receiving the gas into the reservoir and an outlet for discharging the gas from the reservoir;a main valve in pneumatic communication with the outlet of the reservoir and operable between a closed position for closing the outlet to pressurize the reservoir and an open position for opening the outlet to depressurize the reservoir;a pressure line extending pneumatically and communicating between the source of the gas and the main valve to bias the main valve towards the closed position, the pressure line terminating in a port;a sensing valve in pneumatic communication with the port and operable between a closed position to close the port and an open position to open the port and allow the gas from the pressure line to flow therethrough;a delivery outlet in pneumatic communication with the outlet of the reservoir and the gas line to deliver the gas discharged from the reservoir;a sensing passage communicating between the delivery outlet and the sensing valve;wherein, in response to inhalation by the patient through the gas line connected to the delivery outlet, air is drawn through the sensing passage and from the sensing valve to move the sensing valve to the open position to open the port, whereupon the biasing of the main valve is sufficiently reduced for the main valve to move to the open position, whereupon the outlet to the reservoir is opened and the gas therein is discharged from and exits through the delivery outlet to the patient; andwherein the sensing passage is disposed relative to the delivery outlet so that a portion of the gas flowing into the delivery outlet passes through the sensing passage to bias the sensing valve toward the closed position, the sensing valve closing the port when predetermined pressures are achieved in the sensing valve, whereupon the gas from the pressure line moves the main valve to close the reservoir outlet, interrupting delivery of the gas to the patient and permitting repressurizing of the reservoir, whereby the gas is delivered intermittently and is conserved;wherein the sensing passage includes an openi ng at a medial location therein, the opening having a smaller cross-sectional area than adjacent areas of the sensing passage to restrict the flow of gas through the opening. 8. A conserving device for use in delivering gas from a source of gas through a gas line to a patient, the conserving device comprising:a reservoir having an inlet for receiving the gas into the reservoir and an outlet for discharging the gas from the reservoir;a main valve in pneumatic communication with the outlet of the reservoir and operable between a closed position for closing the outlet to pressurize the reservoir and an open position for opening the outlet to depressurize the reservoir;a pressure line extending pneumatically and communicating between the source of the gas and the main valve to bias the main valve towards the closed position, the pressure line terminating in a port;a sensing valve in pneumatic communication with the port and operable between a closed position to close the port and an open position to open the port and allow the gas from the pressure line to flow therethrough;a delivery outlet in pneumatic communication with the outlet of the reservoir and the gas line to deliver the gas discharged from the reservoir;a sensing passage communicating between the delivery outlet and the sensing valve;wherein, in response to inhalation by the patient through the gas line connected to the delivery outlet, air is drawn through the sensing passage and from the sensing valve to move the sensing valve to the open position to open the port, whereupon the biasing of the main valve is sufficiently reduced for the main valve to move to the open position, whereupon the outlet to the reservoir is opened and the gas therein is discharged from and exits through the delivery outlet to the patient;wherein the sensing passage is disposed relative to the delivery outlet so that a portion of the gas flowing into the delivery outlet passes through the sensing passage to bias the sensing valve toward the closed position, the sensing valve closing the port when predetermined pressures are achieved in the sensing valve, whereupon the gas from the pressure line moves the main valve to close the reservoir outlet, interrupting delivery of the gas to the patient and permitting repressurizing of the reservoir, whereby the gas is delivered intermittently and is conserved; andwherein the sensing passage comprises a check valve, the check valve having a check element with opposing sides, the first side facing the sensing valve, the second side facing the delivery outlet, the element movable in response to pressure differences between the opposing sides to open and close the check valve, the check valve having a counterbore defined therein, the counterbore being located so that the air drawn from the sensing valve during inhalation is carried from the first side to the second side of the checking element. 9. The device of claim 7, wherein the sensing valve includes opposing delivery and venting sides, andwherein, when the gas flows from the reservoir to the delivery outlet, a portion of said gas passes through the check valve, flowing from the second side of the check element to the first side, to increase the pressure on the delivery side of the sensing valve to bias the sensing valve toward the closed position. 10. A pneumatic apparatus for delivering pulses of gas from a gas delivery source through a single-lumen cannula in response to inhalation by a patient, the apparatus comprising:a main body having an inlet for receiving gas from a gas source, an outlet delivering the pulses of gas, and a plurality of chambers defined between the inlet and the outlet;the main body includinga regulator pneumatically connected to the inlet for producing a delivery pressure for the gas exiting therefrom;a flow-rate selector secured relative to the regulator so as to receive the gas exiting therefrom, the flow-rate selector having a pressure passage and a variable rate passage ex tending therethrough, the selector including a plurality of orifices defined therein, the orifices sized to correspond to selected oxygen delivery rates of the apparatus, the selector being movably mounted to position a selected one of the orifices in the variable rate passage to cause the gas to exit from the variable rate passage at a selected oxygen delivery rate;a reservoir defined within the main body and having a reservoir inlet and a reservoir outlet, the reservoir located within the main body to receive the gas from the variable rate passage;a main valve located within the main body, the main body comprising a chamber and a movable element received within the chamber, the chamber having a chamber inlet therein, a chamber outlet, and a pressure inlet, the chamber inlet in pneumatic communication with the reservoir outlet, and the pressure inlet in pneumatic communication with the pressure passage of the flow rate selector, the chamber inlet and the pressure inlet disposed in the chamber on opposite sides of the movable element, the movable element being movable to open and close the reservoir outlet;a sensing valve comprising a sensing chamber with a sensing element received therein and a port defined in the sensing chamber, the sensing element movably mounted to seal the port in response to predetermined pressures in the sensing chamber, the sensing element dividing the sensing chamber into two regions;a vent to atmosphere defined in the main body and extending between the sensing chamber and the exterior surface of the main body, the vent to atmosphere being in pneumatic communication with the first of the regions of the sensing chambers;a delivery outlet adapted to connect to the single-lumen cannula;a delivery passage having a delivery end communicating with the delivery outlet and a chamber end communicating with the chamber outlet, the delivery passage receiving gas from the chamber received from the reservoir;a sensing passage disposed within the main body, the sensing passage having a first opening communicating with the delivery outlet and the delivery passage, and a second opening communicating with the second of the regions of the sensing chamber. 11. A pneumatic apparatus for delivering pulses of gas from a gas delivery source through a single-lumen cannula in response to inhalation by a patient, the apparatus comprising:a main body having an inlet for receiving gas from a gas source, an outlet for delivering the pulses of gas, and a plurality of chambers defined between the inlet and the outlet;the main body includinga regulator pneumatically connected to the inlet for producing a delivery pressure for the gas exiting therefrom;a flow-rate selector secured relative to the regulator so as to receive the gas exiting therefrom, the flow-rate selector having a pressure passage and a variable rate passage extending therethrough, the selector including a plurality of orifices defined therein, the orifices sized to correspond to selected oxygen delivery rates of the apparatus, the selector being movably mounted to position a selected one of the orifices in the variable rate passage to cause the gas to exit from the variable rate passage at a selected oxygen delivery rate;a reservoir defined within the main body and having a reservoir inlet and a reservoir outlet, the reservoir located within the main body to receive the gas from the variable rate passage;a main valve located within the main body, the main body comprising a chamber and a movable element received within the chamber, the chamber having a chamber inlet therein, a chamber outlet, and a pressure inlet, the chamber inlet in pneumatic communication with the reservoir outlet, and the pressure inlet in pneumatic communication with the pressure passage of the flow rate selector, the chamber inlet and the pressure inlet disposed in the chamber on opposite sides of the movable element, the movable element being movable to open and close the reservoir outlet;a sensing valve comprising a sensing chamber with a sensing element received therein and a port defined in the sensing chamber, the sensing element movably mounted to seal the port in response to predetermined pressures in the sensing chamber, the sensing element dividing the sensing chamber into two regions;a vent to atmosphere defined in the main body and extending between the sensing chamber and the exterior surface of the main body, the vent to atmosphere being in pneumatic communication with the first of the regions of the sensing chambers;a delivery outlet adapted to connect to the single-lumen cannula;a delivery passage having a delivery end communicating with the delivery outlet and a chamber end communicating with the chamber outlet, the delivery passage receiving gas from the chamber received from the reservoir;a sensing passage disposed within the main body, the sensing passage having a first opening communicating with the delivery outlet and the delivery passage, and a second opening communicating with the second of the regions of the sensing chamber;wherein the main body includes a plate therein and wherein the reservoir and the main chamber are substantially defined in the plate, wherein the main body includes a longitudinal axis and wherein the regulator, the flow rate selector, and the plate are secured to each other along the longitudinal axis. 12. The apparatus of claim 11, wherein the regulator, the flow rate selector, and the plate are each substantially cylindrical and have central axes mounted coaxially with the longitudinal axis of the main body. 13. The apparatus of claim 11, wherein the main body includes an end cap having inner and outer surfaces, wherein the plate includes a plate surface opposing the inner surface of the end cap to define the sensing chamber, and wherein the delivery outlet is defined in the outer surface of the end cap. 14. The apparatus of claim 11, wherein the regulator, the flow rate selector, and the plate are secured in series. 15.A pneumatic apparatus for delivering pulses of gas from a gas delivery source through a single-lumen cannula in response to inhalation by a patient, the apparatus comprising:a main body having an inlet for receiving gas from a gas source, an outlet for delivering the pulses of gas, and a plurality of chambers defined between the inlet and the outlet;the main body including:a regulator pneumatically connected to the inlet for producing a delivery pressure for the gas exiting therefrom;a flow-rate selector secured relative to the regulator so as to receive the gas exiting therefrom, the flow-rate selector having a pressure passage and a variable rate passage extending therethrough, the selector including a plurality of orifices defined therein, the orifices sized to correspond to selected oxygen delivery rates of the apparatus, the selector being movably mounted to position a selected one of the orifices in the variable rate passage to cause the gas to exit from the variable rate passage at a selected oxygen delivery rate;a reservoir defined within the main body and having a reservoir inlet and a reservoir outlet, the reservoir located within the main body to receive the gas from the variable rate passage;a main valve located within the main body, the main body comprising a chamber and a movable element received within the chamber, the chamber having a chamber inlet therein, a chamber outlet, and a pressure inlet, the chamber inlet in pneumatic communication with the reservoir outlet, and the pressure inlet in pneumatic communication with the pressure passage of the flow rate selector, the chamber inlet and the pressure inlet disposed in the chamber on opposite sides of the movable element, the movable element being movable to open and close the reservoir outlet;a sensing valve comprising a sensing chamber with a sensing element received therein and a port defined in the sensing chamber, the sensing element movably mounted to seal the port in response to predetermined pressures in the sensing chamber, the sensing element dividing the sensing chamber into two regions;a vent to atmosphere defined in the main body and extending between the sensing chamber and the exterior surface of the main body, the vent to atmosphere being in pneumatic communication with the first of the regions of the sensing chambers;a delivery outlet adapted to connect to the single-lumen cannula;a delivery passage having a delivery end communicating with the delivery outlet and a chamber end communicating with the chamber outlet, the delivery passage receiving gas from the chamber received from the reservoir;a sensing passage disposed within the main body, the sensing passage having a first opening communicating with the delivery outlet and the delivery passage, and a second opening communicating with the second of the regions of the sensing chamber;wherein the main body comprises a substantially cylindrical housing with a longitudinal central axis, the housing being substantially symmetrical about the longitudinal central axis. 16. A pneumatic apparatus for delivering pulses of gas from a gas delivery source through a single-lumen cannula in response to inhalation by a patient, the apparatus comprising:a main body having an inlet for receiving gas from a gas source, an outlet for delivering the pulses of gas, and a plurality of chambers defined between the inlet and the outlet;the main body includinga regulator pneumatically connected to the inlet for producing a delivery pressure for the gas exiting therefrom;a flow-rate selector secured relative to the regulator so as to receive the gas exiting therefrom, the flow-rate selector having a pressure passage and a variable rate passage extending therethrough, the selector including a plurality of orifices defined therein, the orifices sized to correspond to selected oxygen delivery rates of the apparatus, the selector being movably mounted to position a selected one of the orifices in the variable rate passage to cause the gas to exit from the variable rate passage at a selected oxygen delivery rate;a reservoir defined within the main body and having a reservoir inlet and a reservoir outlet, the reservoir located within the main body to receive the gas from the variable rate passage;a main valve located within the main body, the main body comprising a chamber and a movable element received within the chamber, the chamber having a chamber inlet therein, a chamber outlet, and a pressure inlet, the chamber inlet in pneumatic communication with the reservoir outlet, and the pressure inlet in pneumatic communication with the pressure passage of the flow rate selector, the chamber inlet and the pressure inlet disposed in the chamber on opposite sides of the movable element, the movable element being movable to open and close the reservoir outlet;a sensing valve comprising a sensing chamber with a sensing element received therein and a port defined in the sensing chamber, the sensing element movably mounted to seal the port in response to predetermined pressures in the sensing chamber, the sensing element dividing the sensing chamber into two regions;a vent to atmosphere defined in the main body and extending between the sensing chamber and the exterior surface of the main body, the vent to atmosphere being in pneumatic communication with the first of the regions of the sensing chambers;a delivery outlet adapted to connect to the single-lumen cannula;a delivery passage having a delivery end communicating with the delivery outlet and a chamber end communicating with the chamber outlet, the delivery passage receiving gas from the chamber received from the reservoir;a sensing passage disposed within the main body, the sensing passage having a first opening communicating with the delivery outlet and the delivery passage, and a second opening communicating with the second of the regions of the sensing chamber;wherein the movable element of the main valve comprises a pi ston and the main chamber comprises a cylinder, wherein the piston reciprocates between first and second positions, the first position having the reservoir outlet and the chamber outlet open to deliver gas from the reservoir to the delivery passage, the second position having the reservoir outlet closed to interrupt the flow of gas therefrom. 17. A conserving device for use in delivering gas from a source of gas to a person, the conserving device comprising:a reservoir for holding a volume of gas for delivery to the person, the reservoir having a reservoir inlet for receiving the gas from the gas source and a reservoir outlet for discharging the gas;a delivery system in pneumatic communication with the reservoir to open and close the outlet of the reservoir and to dispense gas intermittently from the reservoir to the person; anda sensing system in pneumatic communication with the person to receive gas to detect a pressure drop upon inhalation by the person, the sensing system also in pneumatic communication with the delivery system to cause the delivery system to open the outlet of the reservoir in response to detecting the pressure drop; anda gas control system pneumatically connected to the gas source, to the delivery system, and to the sensing system, the gas control system increasing the pressure in the sensing system when the gas control system receives gas from the delivery system and, in response to the increased pressure in the sensing system, causing the delivery system to close the outlet of the reservoir and interrupt the delivery of gas to the person;wherein the reservoir is in pneumatic communication with the gas source and is repressurized thereby while the reservoir is closed and depressurized when the reservoir outlet is opened; andwherein the delivery system dispenses a volume of gas from the reservoir at the time the reservoir outlet is opened. 18. The conserving device of claim 17, further comprising a single delivery outlet, the delivery outlet communicating with the delivery passage to delivery gas to the person therethrough and communicating with the sensing system to communicate inhalation by the person to the sensing system. 19. The conserving device of claim 17, further comprising a flow rate selector having an input and an output side, the input side in communication with the gas source and the output side in communication with the reservoir inlet to vary the flow of gas into the reservoir. 20. The conserving device of claim 17, further comprising a regulator for receiving the gas from the gas source and lowering the pressure thereof. 21. The conserving device of claim 17, further comprising means for delivering a pulse of gas having greater volume in response to slower breathing of the person and having lesser volume in response to more rapid breathing of the person. 22. A conserving device for use in delivering gas from a source of gas to a person, the conserving device comprising:a reservoir for holding a volume of gas for delivery to the person, the reservoir having a reservoir inlet for receiving the gas from the gas source and a reservoir outlet for discharging the gas;a delivery system in pneumatic communication with the reservoir to open and close the outlet of the reservoir and to dispense gas intermittently from the reservoir to the person; anda sensing system in pneumatic communication with the person to receive gas to detect a pressure drop upon inhalation by the person, the sensing system also in pneumatic communication with the delivery system to cause the delivery system to open the outlet of the reservoir in response to detecting the pressure drop; anda gas control system pneumatically connected to the gas source, to the delivery system, and to the sensing system, the gas control system increasing the pressure in the sensing system when the gas control system receives gas from the delivery system and, in response to the increased pressure in the sensing system, causing the delivery sys tem to close the outlet of the reservoir and interrupt the delivery of gas to the person;wherein the reservoir is in pneumatic communication with the gas source and is repressurized thereby while the reservoir is closed and depressurized when the reservoir outlet is opened;wherein the delivery system dispenses a volume of gas from the reservoir at the time the reservoir outlet is opened;wherein the delivery system comprises a main valve and a delivery passage, the main valve operable to open and close the reservoir outlet, the delivery passage adapted to be in pneumatic communication with the reservoir outlet when the main valve is open and with the person to receive the gas;wherein the sensing system comprises a sensing valve in a sensing chamber having two regions;wherein the gas control system comprises a pressure line and a sensing passage, the pressure line in communication with the main valve, and the sensing passage communicating between the delivery passage and the sensing chamber. 23. The conserving device of claim 22, wherein the sensing passage of the gas control system comprises a check valve operable between a first position closing the sensing chamber and a second position to open the sensing chamber. 24. A conserving device for use in delivering gas from a source of gas through a gas line to a patient, the conserving device comprising:a reservoir having an inlet for receiving the gas into the reservoir and an outlet for discharging the gas from the reservoir;a main valve in pneumatic communication with the outlet of the reservoir and operable between a closed position for closing the outlet to pressurize the reservoir and an open position for opening the outlet to depressurize the reservoir;a pressure line extending pneumatically and communicating between the source of gas and the main valve to bias the main valve towards the closed position, the pressure line terminating in a port;a sensing valve in pneumatic communication with the port and operable between a closed position to close the port and an open position to open the port and allow the gas from the pressure line to flow therethrough;a delivery outlet in pneumatic communication with the outlet of the reservoir and the gas line to deliver the gas discharged from the reservoir, the delivery outlet in further pneumatic communication with the sensing valve;a check valve communicating between the delivery outlet and the sensing valve;wherein the check valve opens in response to inhalation by the patient through the gas line connected to the delivery outlet to permit air to be drawn from the sensing valve to move the sensing valve to the open position to open the port, whereupon the biasing of the main valve is sufficiently reduced for the main valve to move to the open position, whereupon the outlet to the reservoir is opened and the gas therein is discharged from and exits through the delivery outlet to the patient; andwherein the check valve is disposed relative to the delivery outlet so that a portion of the gas flowing into the delivery outlet passes through the check valve to bias the sensing valve toward the closed position. 25. A conserving device for use in delivering gas from a source of gas through a gas line to a patient, the conserving device comprising:a reservoir having an inlet for receiving the gas into the reservoir and an outlet for discharging the gas from the reservoir;a main valve in pneumatic communication with the outlet of the reservoir; the main valve having a reciprocable element; anda pressure line extending pneumatically and communicating between the source of gas and the main valve to bias the main valve towards the closed position, the pressure line terminating in a port;a sensing valve in pneumatic communication with the port and operable between a closed position to close the port and an open position to open the port and allow the gas from the pressure line to flow therethrough;the reciprocable element of the main valve movabl e between first and second positions, the first position spaced from the reservoir outlet so that said outlet is open and against the port to seal the pressure line; the second position sealing the reservoir outlet so that gas is not dischargeable therefrom and spaced from the port to open the pressure line;wherein the movable element comprises first and second sides having corresponding surface areas, the first side being in pneumatic communication with the reservoir outlet, so that pressurized gas in the reservoir acts on the first side, the second side being in pneumatic communication with the pressure line, so that pressurized gas in the pressure line acts on the second side, andwherein, in the first position, the pressurized gas in the reservoir acts upon a larger surface area than is acted upon by the pressurized gas in the pressure line, and, in the second position, pressurized gas in the reservoir acts upon a smaller surface area than is acted upon by the pressurized gas in the pressure line. 26. A method of delivering pulses of gas to a patient through a cannula, the method comprising:a. providing a housing with a reservoir and a valve located therein in pneumatic communication with a source of gas, the valve having first and second sides with corresponding surface areas;b. receiving gas from the source of gas into the reservoir;c. applying gas from the gas source to the surface area of the first side of the valve to close the reservoir with the second side of the valve, the closed reservoir thereby becoming pressurized;d. applying the pressure in the reservoir over a surface area of the second side of the valve which is smaller than the surface area of the first side to which gas is being applied, whereby the balance of forces exerted on the sides of the valve seals the reservoir;e. relieving the pressure of the gas applied to the first side of the valve, in response to inhalation by the person, by an amount sufficient to change the balance of forces exerted on the valve and unseal the second side of the valve from the reservoir;f. upon unsealing of the reservoir, applying the pressurized gas in the reservoir over substantially the entire surface area of the second side to rapidly increase the force exerted on the second side and move the first side of the valve to seal against the source of gas;g. applying the pressurized gas from the source of gas over a surface area of the first side of the valve which is smaller than the surface area of the second side to which the pressurized gas from the reservoir is being applied, whereby the balance of forces exerted on the sides of the valve seal the first side against the source of gas;h. delivering at least a portion of the volume of gas stored in the reservoir to the patient, the relatively rapid movement of the valve causing a pulse of oxygen to exit the reservoir, the delivery relieving the pressure applied to the second side sufficient to change the balance of forces exerted on the valve and unseal the first side from the source of gas;i. upon unsealing of the source of gas, applying the pressurized gas from the source of gas over substantially the entire surface area of the first side to rapidly increase the force exerted on the first side and reciprocate the valve back to its initial position with the second side of the valve sealed against the reservoir;j. performing steps e through i in response to each inhalation by the person to delivery pulses of oxygen on demand. 27. The method of claim 26, wherein steps e through i occur within the first second after inhalation by the person.