Respirator

A respirator comprising, means for establishing communication with a patient's lungs, means for continuously supplying gas at a predetermined pressure, an expansible and contractible reservoir, a first conduit containing a first valve connected between said supplying means and said communication means, a second conduit containing a second valve connected between said communication means and said reservoir said second conduit including an unobstructed passageway between said reservoir and said second valve, a third conduit containing a third valve downstream from said reservoir and also connected to said second conduit between said reservoir and said second valve, said third conduit communicating with the atmosphere when said third valve is open, means associated with said reservoir for monitoring and indicating the volume of gas received therein, and valve actuating means adapted simultaneously to open the first and third valves and close the second valve during the inspiratory phase and to simultaneously open the second valve and close the first and third valves during the expiratory phase whereby during an expiratory phase said reservoir is connected to said communication means and receives the expired gas, and means associated with said reservoir to maintain a terminal pressure on gas remaining in the lungs at the end of each expiratory phase when said second valve is open.