A respiratory device includes a blower having an inlet and an outlet, a patient interface, and a valve including a valve member that is rotatable through a first angular displacement in a first direction from a first position to a second position. The outlet of the blower is coupled to the patient interface so that positive pressure is provided to a patient's airway via the patient interface when the valve member is in the first position. The inlet of the blower is coupled to the patient interface so that negative pressure is provided to the patient's airway via the patient interface when the valve member is in the second position. The valve member is rotatably oscillated back and forth when the valve member is in the first position and when the valve member is in the second position so that oscillations in the positive pressure and negative pressure, respectively, are provided to the patient's airway.