A respiratory therapy apparatus includes a rocker mechanism (101, 110, 111, 112) that provides an oscillating resistance to expiration. The apparatus also includes an air entrainment arrangement (200) at its air inlet (3) having a ring orifice (214) connected via a gas inlet (4) to a source (119) of oxygen at elevated pressure. The oxygen emerging around the ring orifice (214) entrains ambient air and supplies this as a continuous flow of respiratory gas to the patient interface (2) to provide a positive airway pressure.
