Apparatus for use in administering intermittent positive pressure breathing therapy

Claim 1

IN RESPIRATION APPARATUS INCLUDING A SOURCE OF PRESSURIZED GAS AND DELIVERY MEANS, A PATIENT-CONTROLLED SYSTEM FOR SUPPLYING INTERMITTENTLY GAS FROM SAID SOURCE TO SAID DELIVERY MEANS, COMPRISING: MAIN CONDUIT MEANS COUPLED TO SAID SOURCE AND HAVING A VENT OPENING TO THE ATMOSPHERE; DELIVERY CONDUIT MEANS COUPLED AT ITS OPPOSITE ENDS TO SAID MAIN CONDUIT MEANS AND TO SAID DELIVERY MEANS; VENT VALVE MEANS ADAPTED TO BE CYCLED BETWEEN AN INOPERATIVE CONDITION, WHEREIN FLOW OF GAS TAKES PLACE FROM SAID SOURCE THROUGH SAID MAIN CONDUIT MEANS TO THE ATMOSPHERE THROUGH SAID VENT OPENING, AND AN OPERATIVE CONDITION, WHEREIN THE FLOW OF GAS IS FROM SAID SOURCE THROUGH SAID MAIN AND DELIVERY CONDUIT MEANS TO SAID DELIVERY MEANS; A VENTURI IN SAID DELIVERY CONDUIT MEANS; AND CONTROL MEANS INCLUDING PRESSURE-SENSING MEANS COUPLED TO SAID VENTURI AT THE THROAT THEREOF AND TO SAID DELIVERY CONDUIT MEANS AT A LOCATION SPACED FROM SAID VENTURI; MEANS CONNECTING SAID CONTROL MEANS AND SAID VENT VALVE MEANS TO CYCLE SAID VENT VALVE MEANS BETWEEN SAID INOPERATIVE AND SAID OPERATIVE CONDITION, AND MEANS FOR PREVENTING A NEGATIVE PRESSURE SIGNAL IN SAID DELIVERY CONDUIT MEANS ADJACENT SAID DELIVERY MEANS FROM ACTING ON SAID CONTROL MEANS THROUGH THE COUPLING TO SAID DELIVERY CONDUIT MEANS SPACED FROM THE VENTURI, BUT PERMITTING SUCH SIGNAL TO ACT ON SAID CONTROL MEANS THROUGH THE COUPLING AT THE THROAT OF SAID VENTURI, SAID CONTROL MEANS BEING RESPONSIVE TO A PREDETERMINED NEGATIVE PRESSURE SIGNAL IN SAID DELIVERY CONDUIT MEANS ADJACENT SAID DELIVERY MEANS FOR CYCLING SAID VENT VALVE MEANS TO ITS OPERATIVE CONDITION AND TO A PREDETERMINED TERMINAL FLOW THROUGH SAID DELIVERY CONDUIT MEANS INDEPENDENT OF ABSOLUTE PRESSURES THEREIN FOR CYCLING SAID VENT VALVE MEANS TO ITS INOPERATIVE CONDITION.