Abstract: A carrier gas source is connected to the breathing system of a patient by a carrier-gas conduit. A positive displacement gas pump has an outlet connected to a distal port in the carrier-gas conduit. A pump gas-supply conduit, includes a vaporizer chamber and an ambient-referenced pressure regulator which has an output orifice connected indirectly to the positive displacement pump inlet. In one kind of anesthetic-vapor delivery apparatus, for use with high boiling anesthetic agents, the pump gas-supply conduit has an input end connected to a proximal port in the carrier-gas conduit. In another kind of anesthetic-vapor delivery apparatus, for use with lower temperature anesthetic agents there is no proximal port. In both kinds of anesthetic-vapor delivery apparatus, the ambient-referenced regulator controls the pressure at the pump inlet to a narrow range of pressures just below ambient atmospheric pressure.

Abstract: A hot wire sensor has a cylindrical light-transparent tube having two opaque patches adjacent the two tube ends, respectively, and with one platinum "hot" wire mounted about centrally therein and another platinum wire mounted adjacent thereto. A gas flow monitor includes a resistive bridge circuit, connected to the hot wire sensor. In the bridge circuit, the two platinum wires become two of the adjacent bridge branches. A DC voltage supply of the monitor is connected across the bridge at the bridge junction of the platinum wires, heating the one but not the other owing to disparate resistances in the bridge branches. A calibration socket is mounted vertically on an outer wall of the monitor housing. To calibrate the sensor, a tube end is inserted into the socket holding the tube axis horizontal and the tube is rotated until the opaque patch breaks a light beam between a LED and a photo transistor at the periphery of the socket.

Abstract: A hot wire sensor has a cylindrical light-transparent tube having two opaque patches adjacent the two tube ends, respectively, and with one platinum "hot" wire mounted about centrally therein and another platinum wire mounted adjacent thereto. A gas flow monitor includes a resistive bridge circuit, connected to the hot wire sensor. In the bridge circuit, the two platinum wires become two of the adjacent bridge branches. A DC voltage supply of the monitor is connected across the bridge at the bridge junction of the platinum wires, heating the one but not the other owing to disparate resistances in the bridge branches. A calibration socket is mounted vertically on an outer wall of the monitor housing. To calibrate the sensor, a tube end is inserted into the socket holding the tube axis horizontal and the tube is rotated until the opaque patch breaks a light beam between a LED and a photo transistor at the periphery of the socket.

Abstract: A vaporizer has a main conduit supplied at an inlet end by a carrier gas of oxygen and nitrous oxide having a constant flow rate. The outlet end of the conduit is connected to the breathing system of a patient. A series circuit with an input end connected to a proximal port in the conduit includes a check valve, a chamber in which anesthetic vapor is maintained in saturation and a positive displacement pump driven by an electrical motor for pumping the vapor-saturated gas at a rate that is only a function of an electrical signal applied to the motor. The output of the pump is connected to a distal port of the conduit. More than one such chamber may be provided, each containing a different liquid anesthetic, and any one being connected into the circuit by means of a selector valve.

Abstract: A pulmonary ventilator system has a bellows assembly and a source of driving gas connected by a series branch including an electrically-controlled switching valve and a motor-controlled flow-rate-controlling valve. A controller including a microprocessor senses the position of the flow-rate-controlling valve via a mechanical to electrical transducer and has outputs connected to and controlling the switching valve and the motor. It has programmed in its memory the maximum flow rate capacity of the flow-rate-controlling valve and the maximum capacity of the bellows. The microprocessor is capable of receiving from an operator his target values for minute volume, breathing rate and expiration time to inspiration time ratio.

Abstract: A pulmonary ventilator-bellows-assembly kit includes a base to which a large (adult) cylindrical housing and a small (pediatric) housing, either one of which are mountable and sealable to the same peripheral base portion. Also included are a large bellows mountable directly to the base and a small bellows that is mountable to the base via an adaptor. The cylindrical housings to base mounting means use a bayonet type lock and an O-ring seal so that mounting is simply and easily accomplished by inserting a housing and twisting it over the base. The small-bellows adaptor also seals to the base using an O-ring and the small housing automatically locks it into place. The adaptor is adapted to be stored on the base when the large bellows and large housing are mounted and in use.

Abstract: A converter has a pressure to voltage transducer connected to an amplifier. A laminar gas flow element (L.F.E.) may be connected to the transducer and the converter output voltage is a measure of the gas flow rate through the L.F.E. The converter gain may be switched from one value when one kind of anesthetic gas is being monitored to another gain values when a second gas is used. The ratio of the one gain values to the second is made equal to the ratio of viscosities of the second gas to that of the first so that recalibration is not necessary when the kind of gas in use is changed. Further, the absolute values of the stepped gains with fixed ratio are adjusted vernierly to produce a predetermined output voltage for each L.F.E. with a known rate of gas flowing, which absolute gain value in each case may be recorded as a characterization of each particular L.F.E. After such characterizations are made, no further calibrations of L.F.E. or converters are needed and any L.F.E.

Abstract: A medical ventilator is disclosed for switching and mixing oxygen with air in a driving and oxygen mixing means (2) and delivering the mixture to a gas flow control apparatus (3) for application directly to a patient breathing apparatus (5) or to storage in a bellows reservoir (81) of a continuous positive airway pressure facility (4). The ventilator is equipped with a control module (1) having directly set control adjustments (6-9, 105-112) for determining respiratory rate, inspiration-to-expiration ratio, oxygen concentration and the prescribed minute volume of the oxygen mixture to be delivered to a patient. The adjustment control circuitry which performs the calculations, logic and drive operations for switching and mixing oxygen in plural chambers (14, 18, 29, 30) of module (2), the switching of the mixture through module (3), and sensing fill and refill needs of reservoir (81). Module (4) includes apparatus (83, 84) for exerting a positive pressure on the oxygen in reservoir (81).

Abstract: An anesthesia ventilator is disclosed for controlling the flow of air and/or oxygen through a plurality of binary weighted valves from a fluid regulator source to a bellows assembly. Directly-set minute volume, breath rate and inspiration to expiration ratio controls operate electronic circuitry which adjusts the magnitude of the flow, the tidal volume and the inhalation to exhalation times. The circuitry includes alarm detecting devices for alerting personnel that a patient should be ventilated manually, that a patient is disconnected from the instrument, that control settings exceed specifications for the instrument, that undesired low gas pressure exists and that actual inspiration to expiration is less than that of the control setting. Flow and tidal volume limiting apparatus is provided, together with sigh circuitry and devices for correcting for altitude and gas parameters.