Methods for detecting a patient disconnecting from a continuous positive airway pressure (CPAP) therapy device are disclosed. A cyclical pressure difference signal is derived based upon measurements from a patient interface pressure sensor and from a source pressure sensor. The pressure difference signal is integrated to generate a resultant integral signal for each respiratory cycle, which is comprised of at least one inspiratory phase and at least one expiratory phase as represented by the corresponding portions of the pressure difference signal. A pressure source of the CPAP therapy device is deactivated in response to a disconnect condition being evaluated from the integral signal. In one embodiment, the disconnect condition is the integral signal exceeding a predefined disconnect threshold. In other, it is a slope value corresponding to a rate of increase of the integral signal exceeding a predefined threshold for a predefined duration.
