Apparatus and methods provide control for generation of a flow of air to a patient's airways for different respiratory therapies. The pressure and a flow rate may be simultaneously controlled so as to provide a pressure therapy and a flow therapy. The system may include one or more flow generators, in which the control of the pressure and flow rate may include altering the output of one or more of the flow generators and/or an optional adjustable vent. The pressure and flow rate may each be held at a constant. One or both of the pressure and flow rate may also vary in accordance with a desired therapy. The air may be provided via a patient interface that includes a vent to atmosphere, which may be the adjustable vent. The vent may be actuated by a controller to implement the simultaneous control of pressure and flow rate of the air.