A respiratory mask assembly for delivering breathable gas to a patient includes a frame and an elbow assembly. The frame has a front surface and a rear surface adapted in use to face the patient. The frame includes a main body providing an aperture therethrough for the introduction of breathable gas into a nasal breathing cavity. The elbow assembly is swivelably coupled to the front surface of the frame. The elbow assembly includes a swivel elbow that defines an intake port and an exhaust port separated from the intake port using a baffle. The elbow assembly includes an end portion that interfaces with the aperture of the frame.

A mask system for delivering air pressurized above atmospheric pressure to the airways of a patient to treat sleep disordered breathing (SDB) by continuous positive airway pressure (CPAP) may include a mask having a cushion configured to form a seal with the patient's nose; two inlet conduits, each of the two inlet conduits configured to extend from a position superior to the patient's head and along a corresponding side of the patient's head, and each of the two inlet conduits being in fluid communication with a corresponding side of the mask to deliver pressurized air to the mask; a first vent arrangement configured to be positioned superior to the patient's head in use and configured to discharge gas to atmosphere during therapy; and a second vent arrangement configured to be positioned inferior to the first vent arrangement in use and configured to discharge gas to atmosphere during therapy.

A mask system for delivering air pressurized above atmospheric pressure to the airways of a patient to treat sleep disordered breathing (SDB) by continuous positive airway pressure (CPAP) may include a mask having a cushion configured to form a seal with the patient's nose; two inlet conduits, each of the two inlet conduits configured to extend from a position superior to the patient's head and along a corresponding side of the patient's head, and each of the two inlet conduits being in fluid communication with a corresponding side of the mask to deliver pressurized air to the mask; a first vent arrangement configured to be positioned superior to the patient's head in use and configured to discharge gas to atmosphere during therapy; and a second vent arrangement configured to be positioned inferior to the first vent arrangement in use and configured to discharge gas to atmosphere during therapy.

Aspects of the present technology comprise a positioning and stabilising structure to hold a seal-forming structure in a therapeutically effective position on a head of a patient. The seal-forming structure may be constructed and arranged to form a seal with a region of the patients face surrounding an entrance to the patients airways for sealed delivery of a flow of air at a therapeutic pressure of at least 4 cmH2O with respect to ambient air pressure throughout the patients respiratory cycle in use. The positioning and stabilising structure may comprise a front hoop arranged to contact, in use, at least a region of the patients head superior to an otobasion superior of the patients head and a rear strap. The positioning and stabilising structure may comprise an adjustment mechanism for adjustment of the front hoop and the rear strap relative to the patients head, the adjustment mechanism being arranged in a single operation to adjust both the front hoop and rear strap to enable the positioning and stabilising structure to fit different size heads.

Aspects of the present technology comprise a positioning and stabilising structure to hold a seal-forming structure in a therapeutically effective position on a head of a patient. The seal-forming structure may be constructed and arranged to form a seal with a region of the patients face surrounding an entrance to the patients airways for sealed delivery of a flow of air at a therapeutic pressure of at least 4 cmH2O with respect to ambient air pressure throughout the patients respiratory cycle in use. The positioning and stabilising structure may comprise a front hoop arranged to contact, in use, at least a region of the patients head superior to an otobasion superior of the patients head and a rear strap. The positioning and stabilising structure may comprise an adjustment mechanism for adjustment of the front hoop and the rear strap relative to the patients head, the adjustment mechanism being arranged in a single operation to adjust both the front hoop and rear strap to enable the positioning and stabilising structure to fit different size heads.

A patient interface comprises a plenum chamber and a seal-forming structure. The seal-forming structure comprises a support structure arranged to support a sealing portion that is adapted to sealing engage the patient's face in use. The seal-forming structure may also include a seal biasing portion configured to inflate under pressurization within the cavity in the cushion assembly in use to extend the reach of the sealing portion and decouple the sealing portion from external forces.

A patient interface comprises a plenum chamber and a seal-forming structure. The seal-forming structure comprises a support structure arranged to support a sealing portion that is adapted to sealing engage the patient's face in use. The seal-forming structure may also include a seal biasing portion configured to inflate under pressurization within the cavity in the cushion assembly in use to extend the reach of the sealing portion and decouple the sealing portion from external forces.

A patient interface includes: a plenum chamber; a seal-forming structure; a positioning and stabilising structure; a plenum chamber insert configured to be positioned and retained within the plenum chamber; and a vent structure; wherein the plenum chamber insert has a plenum chamber insert port; wherein the plenum chamber insert has an exterior surface configured to be positioned adjacent to an interior surface of the plenum chamber; wherein when the plenum chamber insert is positioned and retained within the plenum chamber, a radial channel is formed by the interior surface of the plenum chamber and the exterior surface of the plenum chamber insert such that gas is able to pass between a patient-proximal side plenum chamber insert and a patient-distal side of the plenum chamber insert via the radial channel during use.

A patient interface includes: a plenum chamber; a seal-forming structure; a positioning and stabilising structure; a plenum chamber insert configured to be positioned and retained within the plenum chamber; and a vent structure; wherein the plenum chamber insert has a plenum chamber insert port; wherein the plenum chamber insert has an exterior surface configured to be positioned adjacent to an interior surface of the plenum chamber; wherein when the plenum chamber insert is positioned and retained within the plenum chamber, a radial channel is formed by the interior surface of the plenum chamber and the exterior surface of the plenum chamber insert such that gas is able to pass between a patient-proximal side plenum chamber insert and a patient-distal side of the plenum chamber insert via the radial channel during use.

A gas washout vent, and a patient interface with the gas washout vent, configured to allow patient-exhaled CO.sub.2 to flow to an exterior of the plenum chamber to minimise rebreathing of exhaled CO.sub.2 by the patient, the gas washout vent including at least one outlet orifice; a diffusing member at least partly covering the outlet orifice; and a blocking member having an air-impermeable material, the blocking member preventing gas exiting from the outlet orifice from flowing straight through the diffusing member.