Abstract: A demand responsive flow controller for use in a respiration system for the administration of oxygen from a pressurized source through a cannula to a patient is disclosed. A flow path between the pressurized source and the cannula is opened and closed by a fluidic valve which is responsive to the presence and absence of a low pressure power stream developed by a flow restrictor coupled to the pressurized source. The low pressure power stream is applied to the control port of the on/off fluidic valve by a monostable fluidic switch which conducts the low pressure power stream through the valve control port of the on/off valve in response to expiration by the patient, and which diverts the low pressure power stream away from the on/off valve in response to inspiration by the patient.