A liquid injector for medical respirators in which a predetermined quantity of patient gas is stored at higher than atmospheric pressure in a known volume during an expiratory period of a respiratory cycle and discharged to a patient during the next following inspiratory period of the cycle. The injector includes a movable member the displacement of which from a datum position controls the quantity of liquid injected into the patient gas in each cycle. This displacement is directly proportional to the pressure of the stored patient gas and the movable member is displaced by driving means which is driven as a result of the pressure.
A displacement metering device for administering a mixture of oxygen and an anesthetic gas to a patient measures single dose quantities of each of the two gases in separate sets of gas displacing means and dispenses a dose of each gas in admixture to a patient during the inspiration phase of the patient's respiratory cycle. Coordinating means ensure that the two gases are delivered in constant ratio and also provide means for changing the ratio between the two gases. Means are also provided to change the volume, or dose size, of the two administered gases.
A variable flow reciprocating piston respirator system which is capable of providing a substantially constant oxygen enrichment over an entire inspiration stroke of a variable flow respirator output. A proportional control valve is used to deliver oxygen from an oxygen supply tank to the output of a reciprocation piston pump. A microprocessor controls the magnitude of opening of the proportional valve to insure that a proper overall volume of the output is produced with the proper percentage of enrichment of oxygen.
