An apparatus (10) is provided for controlling discharge of oxygen from an oxygen supply source (12) to a patient. The apparatus includes an oxygen supply inlet (47), a pressure regulator (14) coupled to the oxygen supply inlet and configured to reduce pressure of oxygen received from the oxygen supply inlet to a selected magnitude, a flow controller (16) coupled to the pressure regulator (14) and configured to meter oxygen received from the pressure regulator at a selected flow rate, and an oxygen distribution assembly including a pneumatic demand oxygen valve (18) and a conduit (51) conducting oxygen discharged from the flow controller through the pressure regulator to the pneumatic demand oxygen valve for delivery to a patient. The flow controller (16) includes a chamber (110) and a rotary valve (112) for splitting oxygen discharged from chamber (110) into a first stream in an oxygen supply passageway (51) for use by a patient and a second stream in a diaphragm supply passageway (48) for controlling operation of pneumatic demand oxygen valve.
