A respiratory assistance device is disclosed. There is a patient interface for coupling to a patient respiratory passageway, and a selectively regulated therapeutic gas flow source in pneumatic communication with the patient over the patient interface. A controller is connected to the therapeutic gas flow source and is receptive to inputs of a prescription pressure level and an initial delay duration. After the patient dons the patient interface, therapeutic gas flow is restricted for the initial delay duration following receipt of a treatment initiation command. Upon the expiry of the initial delay duration, the controller increases therapeutic gas flow to the prescription pressure level.
