Automatic intermittent positive pressure ventilators

Claim 1

A MECHANICAL VENTILATOR COMPRISING: (A) A VENTILATING GAS SUPPLY CONDUIT FOR CONDUCTING VENTILATING GAS TO AN INHALATING PATIENT INCLUDING A VARIABLE VOLUME VENTILATING GAS RESERVOIR; (B) A VENTILATING GAS SUPPLY PORT FOR SUPPLYING VENTILATING GAS TO THE VENTILATING GAS SUPPLY CONDUIT; (C) MEANS FOR CONTRACTING THE VOLUME OF THE VENTILATGAS RESERVOIR; (D) A SOURCE OF DRIVING FLUID UNDER PRESSRE, THE FLUID BEING ISOLATED FROM THE VENTILATING GAS; (E) MEANS FOR CONTRACTING THE VOLUME OF THE VENTILATING GAS RESERVOIR RESPONSIVE TO DRIVING FLUID PRESSURE; (F) CHECK VALVE MEANS FOR OPENING THE VENTILATING GAS SUPPLY PORT RESPONSIVE TO EXPANSION OF THE VENTILATING GAS RESERVOIR AND FOR CLOSING THE VENTILATING GAS SUPPLY PORT RESPONSIVE TO CONTRACTION OF THE VENTILATING GAS RESERVOIR; (G) A NON-REBREATHING VALVE MEANS FOR EXHAUSTING EXHALED GAS AWAY FROM THE PATIENT; (H) A FIRST LIMIT FOR VOLUMETRICALLY LIMITING EXPANSION OF THE VENTILATING GAS RESERVOIR; A SECOND LIMIT MEANS FOR VOLUMETRICALLY LIMITING THE CONTRACTION OF THE VENTILATING GAS RESERVOIR; AND MEANS FOR CAUSING EXPANSION TO COMMENCE WITHOUT SIGNIFICANT TIME DELAY WHEN THE VOLUMETRIC LIMIT ON CONTRACTION IS REACHED; (I) ADJUSTABLE PRESSURE-RESPONSIVE MEANS RESPONSIVE TO AND ACTUATED BY VENTILATING GAS PRESSURE IN THE VENTILATING GAS SUPPLY CONDUIT, THE PRESSURE-RESPONSIVE MEANS HAVING A VARIABLE SETTING THAT CAN BE PRESET TO RESPOND WHEN A PREDETERMINED MAXIUM VENTILATING GAS PRESSURE VALUE BUILDS UP IN THE VENTILATING GAS SUPPLY CONDUIT CAUSED BY INCREASING IMPEDANCE IN THE PATIENT; (J) A THIRD LIMIT MEANS ACTUATED BY RESPONSE OF THE PRESSURE-RESPONSIVE MEANS TO LIMIT FURTHER CONTRACTION OF THE VENTILATING GAS RESERVOIR BEFORE THE VOLUMETRIC LIMIT ON CONTRACTION IMPOSED BY THE SECOND LIMIT MEANS IS REACHED; AND (K) CONTROL MEANS RESPONSIVE TO ACTUATION OF THE THIRD LIMIT MEANS, THE CONTROL MEANS, WHEN ACTUATED, RELEASLING DRIVING FLUID PRESSURE FROM THE MEANS FOR CONTRACTING THE VENTILATING GAS RESERVOIR, THEREBY CAUSING EXPANSION OF THE VENTILATING GAS RESERVOIR TO IMMEDIATELY COMMENCE; (L) WHEREBY THE VENTILATING GAS RESERVOIR CYCLES WITH A CONSTANT STROKE-VOLUME AND SUPPLIES A CONSTANT AMOUNT OF VENTILATING GAS TO THE PATIENT OVER A GIVEN TIME INTERVAL UNTIL THE PREDETERMINED MAXIMUM PRESSURE VALUE IS REACHED RESPONSIVE TO INCREASING IMPEDANCE IN THE PATIENT, WHEN THE RESERVOIR, UPON RESPONSE OF THE PRESSURE-RESPONSIVE MEANS AND ACTUATION OF THE THIRD LIMIT MEANS AND CONTROL MEANS AUTOMATICALLY PRESSURE-CYCLES WITH A VARIABLE STROKEVOLUME IN WHICH THE STROKE-FREQUENCY INCREASES PROPORTIONATELY WITH DECRESE OF STROKE-VOLUME TO EFFECTIVELY MAINTAIN SUBSTANTIALLY THE SAME CONSTANT AMOUNT OF VENTILATING GAS OVER A GIVEN TIME INTERVAL TO THE PATIENT, BUT AT A SAFEY LIMITED MAXIMUM PRESSURE, UNTIL PATIENT IMPEDANCE DECREASES SUFFICIENTLY TO CAUSE VENTILATING GAS PRESSURE IN THE VENTILATING GAS SUPPLY CONDUIT TO REMAIN BELOW THE PREDETERMINED MAXIMUM PRESSURE VALUE, AND THE RESERVOIR AUTOMATICALLY RESUMES CYCLING WITH A CONSTANT STROKEVOLUME.