A mechanical insufflation-exsufflation device including an air source to provide positive airway pressure (PAP); a patient interface; at least one sensor to sense air pressure and flow at the patient interface; and a controller to control the air source to deliver at least one mechanically assisted cough to the patient in response to at least one of a target breathing flow and a target inhalation time period being sensed by the at least one sensor, and when the at least one of a target breathing flow and a target inhalation time period is not sensed, the controller is configured to control the air source to deliver each in a series of high-level PAP provided over a duration being followed by a low-level PAP provided over a duration, the series of high-level PAP increasing in pressure level and duration from a prior one in the series of high-level PAP.