Demand responsive flow controller

For use in a respiration system for the administration of oxygen from a supply conduit through a delivery conduit and cannula to a patient, a demand responsive flow controller comprising, in combination:

• a flow restrictor adapted to be coupled to the supply conduit for conducting a control power stream;
• an on/off fluidic valve having an inlet port adapted to be coupled to the supply conduit, an outlet port adapted to be coupled to the delivery conduit, and a valve control port for closing and opening a fluid flow path between said inlet and outlet ports in response to the application and removal of the control power stream to and from the valve control port, respectively;
• a fluidic switch having an inlet port coupled to the output of the flow restrictor, a gate control port for receiving a respiration signal, a discharge port coupled to said valve control port through which the control power stream is conducted only in response to a respiration signal at said control port corresponding with expiration, and a vent port communicating to atmosphere through which the power stream is conducted only in response to a respiration signal at said control port corresponding with inspiration;
• and,
• a fluidic transducer adapted to be coupled in fluid communication with the cannula and and including means in movable engagement with the gate control port of the fluidic switch for producing the respiration signals by opening and closing said gate control port to ambient pressure in response to cannula pressure fluctuations corresponding with inspiration and expiration, respectively.