Respiratory mask

A flexible patient interface structure arranged to sealingly interface with and deliver breathable gas to a nose of a patient in use, the flexible patient interface structure comprising:

• a posterior portion comprising at least one thin flexible membrane configured to form a seal with the patient's face in use, a wall thickness of the posterior portion being varied;
• an anterior portion with a central gas washout vent region, a wall thickness of the anterior portion being thicker at the central gas washout vent region than at other adjacent regions;
• a first laterally extending protrusion configured to receive the breathable gas from an air delivery tube or air delivery tube connector;
• and
• a second laterally extending protrusion configured to receive the breathable gas from the air delivery tube or the air delivery tube connector,
• wherein the posterior portion and the anterior portion form a chamber,
• wherein the central gas washout vent region is located between the first and second laterally extending protrusions and comprises an array of vent openings,
• wherein each of the first and second laterally extending protrusions terminates at a distal end that is furthest from the other laterally extending protrusion, and
• wherein the first and second laterally extending protrusions lack an outwardly extending circumferential flange at the distal end.

A flexible patient interface structure arranged to sealingly interface with and deliver breathable gas to a nose of a patient in use, the flexible patient interface structure comprising:

• an elastomeric main body that forms a plenum chamber and has an anterior surface and a posterior surface, the posterior surface being configured to sealingly engage the patient's face and wall thickness of the posterior surface being varied;
• a first protrusion extending laterally from the elastomeric main body and configured to receive the breathable gas from an air delivery tube or air delivery tube connector;
• a second protrusion extending laterally from the main body and configured to receive the breathable gas from an air delivery tube or air delivery tube connector;
• and
• a central gas washout vent region located on the anterior surface of the plenum chamber between the first and second protrusions and comprising an array of vent openings, a wall thickness of the anterior surface of the plenum chamber being greater at the central gas washout vent region than other adjacent regions of the main body,
• wherein the first and second protrusions lack an outwardly extending circumferential flange at their terminal ends.