A fluid flow control apparatus (2) for use in, for example, a patient interface (200), is provided that includes a main conduit (4) structured to receive a pressurized fluid and a nozzle assembly (6) coupled to the main conduit. The nozzle assembly includes an external nozzle element (8) having a contoured top surface (14) and a main bore (26) in fluid communication with an interior (46) of the main conduit, an internal nozzle element (10) received within the main bore, wherein a gap (48) is provided between the internal nozzle element and the external nozzle element, and a switching element selectively moveable between a first position and a second position, wherein in the first position, the switching element (12) is positioned below the contoured top surface of the external nozzle element, and wherein in the second position, at least a portion of the switching element is positioned adjacent to or above the contoured top surface of the external nozzle element.
