Abstract: A resuscitation/ventilation apparatus incorporates an entrainment mixer with a nozzle, discharging entraining gas into an entrainment chamber, the nozzle being connected with a high pressure source of the entraining gas. One entrainment port to the entrainment chamber is connected to atmosphere and another entrainment port is connected to an oxygen source. A continuously variable restriction is disposed in the oxygen supply conduit upstream of the other entrainment port and is variable independently of any control of the entraining gas supply, to enable delivery of a gas mixture of steplessly variable oxygen concentration.

Abstract: A ventilator for inducing or assisting lung function in humans is characterized by a control system that provides for semi-automatic operation in which a single complete ventilation cycle in accordance with predetermined ventilation parameters (tidal volume, durations of inhalation and exhalation phases) is initiated by operation of a trigger. The ventilator is particularly useful in one-man resuscitation by CPR. The control system may require a discrete trigger operation to initiate each successive ventilation cycle or it may provide for continuous operation with timed successive cycles, in the manner of an automatic ventilator, by holding or latching the trigger. Various embodiments based on gas-powered ventilators are disclosed but the invention is also applicable to electrically operated or controlled ventilators. In a typical embodiment (FIG.

Abstract: A portable resuscitator/ventilator device especially intended for emergency use and powered by pressurized primary breathable gas such as oxygen or compressed air from a bottle comprises a control unit that outputs primary gas pulses to a patient valve that includes an entrainment mixer for diluting the primary gas with air. The entrainment mixer is selectively operable to that the patient valve delivers primary gas or air-diluted primary gas as required. The control unit includes a fixed value flow-control restrictor that passes a required tidal volume of primary gas for undiluted delivery to the patient and the impedance of the patient valve is arranged to increase when the entrainment mixer is operational so that flow of the primary gas is automatically reduced to provide the required tidal volume of air-diluted primary gas without wastage of primary gas or any adjustment of the control unit.

Abstract: A pressure fluid-actuated oscillator, especially suitable for use in lung ventilation equipment for emergency use, comprises a double-piloted 5-port valve and biased timer valves controlling the supply to its pilots to provide for repeated changeover of the 5-port valve at intervals determined by the respective timing periods of the timer valves. One of the timer valves has an adjustable timing period whereas the other has a nominally fixed timing period but is made sensitive to the duration of the immediately preceding timing period determined by the adjustable timer valve so as automatically to change its timing period in the same sense as adjustment of the adjustable timer valve.In lung ventilation equipment using such an oscillator, therefore, a single control may serve for directly setting the critical inhalation phase duration and to cause a complementary alteration of the exhalation phase duration that maintains the ratio of duration of the respective phases within desirably close limits.

Abstract: Lung ventilation equipment comprising a gas pulse source delivering pulses of breathable gas to a patient valve for introduction into the respiratory system of a patient for resuscitation or anaesthetic purposes is characterized by a restrictor in the pulse delivery line from the pulse source to the patient valve, the restrictor being constructed to operate in a sonic-flow "choked" condition during passage of a gas pulse therethrough so that system pressures and resistances downstream of the restrictor cannot affect operation of the pulse source. Downstream of such a restrictor, therefore, conduits may be of small bore while the patient valve may be of the low-pressure type that normally requires a large-bore supply conduit.

Abstract: A gas valve mechanism especially suitable for use as the patient valve in conjunction with a lung ventilator or resuscitation device by developing high actuating forces from low pressure gas supplies comprises a valve element movable in a body having a gas pulse inlet, a gas pulse outlet and an exhaust outlet. The valve element has a large effective area exposed to the gas pulse inlet and is moved by gas pressure at that inlet, against spring-loading, to open a restricted flow path to the gas pulse outlet, the flow path restriction developing a pressure differential acting to oppose the spring loading and hold the valve element positively in the flow path open position.