CPAP treatment apparatus (10), as one form of
positive pressure ventilatory assistance, is disclosed. A
turbine / blower (14), operated by a mechanically coupled electrical motor (16), receives air or breathable gas at an inlet (18) thereof, and supplies the breathable gas at a delivery pressure to a delivery tube / hose (20) having connection at the other end thereof with a
nose mask (12). A
microcontroller (38) has an operational "
Mask-Fit" mode. An initial
constant pressure level is applied by the blower (14) to the
mask (12). If the functional mode is a Manual mode, then the
mask-fit test pressure is the current "set' pressure. If the functional mode is the Automatic
Titration mode, the mask-fit test pressure is the 95th percentile pressure of the previous session, otherwise it is the base treatment pressure, e.g. 10-12 cm H2O. This
constant pressure is applied for a period of time, typically 1-3 minutes. The
microcontroller (38) continuously determines mask leak as the value, fLEAK, from a flow sensor (32), comparing this to a threshold, and providing the patient with a visual indication of degree of leak. In this way the patient can manipulate the mask to ensure correct fitting as indicated by the appropriate message or indication.