PATIENT INTERFACE WITH VOLUME REDUCING MEMBER

The invention relates to a patient interface; said patient interface comprising: a cushion assembly adapted to form a seal around the patient's nose and/or mouth, the cushion assembly forming a plenum chamber; a gas washout vent; at least one baffle member arranged to separate the plenum chamber into a main chamber and at least one peripheral chamber; a heat and moisture exchanger positioned within the main chamber in direct fluid communication with the entrance to the patient's airways and positioned in the flow path between the patient's airways and the gas washout vent; and at least one leak port provided to an anterior side of the heat and moisture exchanger, wherein the at least one leak port is arranged to allow any inspiratory flow into the at least one peripheral chamber to bypass the heat and moisture exchanger prior to flowing into the at least one peripheral chamber.