Patient interface

A seal-forming structure for a patient interface, the seal-forming structure constructed and arranged to form a seal with a region of a patient's face surrounding an entrance to the patient's airways, the seal-forming structure constructed and arranged to maintain a therapeutic pressure of at least 6 cmH2O above ambient air pressure in a plenum chamber throughout the patient's respiratory cycle in use, the plenum chamber having a plenum chamber inlet port configured to receive a flow of pressurised air at the therapeutic pressure, the seal-forming structure comprising:

• a patient-contacting surface configured to engage the patient's facial skin to form a seal;
• a posterior opening formed in the patient-contacting surface, the posterior opening configured to provide the flow of air at said therapeutic pressure to the patient's nares;
• and
• a support structure extending from a first location on the patient-contacting surface to a second location on an interior surface of the seal-forming structure, the support structure and the interior surface forming a continuous loop,
• wherein the patient interface is configured to allow the patient to breath from ambient through their mouth in the absence of a flow of pressurised air through the plenum chamber inlet port, or the patient interface is configured to leave the patient's mouth uncovered, and
• wherein a superior portion of the seal-forming structure is structured to engage the patient's nose inferior to the patient's nasal bone.