Patent ID: 7770579

Claim:
A method for determining a flow characteristic of a patient interface for a device that delivers positive airway pressure treatment to a patient, the method comprising the steps of: providing a positive airway pressure treatment apparatus with a patient interface; delivering a plurality of flow levels in a predetermined test range through the patient interface while the patient interface is unblocked and disengaged from a patient in a manner that will not apply pressure to the airway of the patient; measuring flow through the patient interface; measuring pressure at a remote location from the patient interface; generating an impedance table from values of pressure and flow measured during the step of delivering, said values of pressure and flow associated with each of the plurality of flow levels in the predetermined test range; and determining a flow characteristic of the patient interface from the impedance table by linearly interpolating a value from values in the impedance table during the provision of positive airway pressure treatment to a patient.