Seal-forming structure with multiple curvatures

A patient interface for sealed delivery of a flow of air at a continuously positive pressure with respect to ambient air pressure to an entrance to a patient's airways including at least an entrance of a patient's nares, wherein the patient interface is configured to maintain a therapy pressure in a range of about 4 cmH2O to about 30 cmH2O above ambient air pressure in use, throughout a patient's respiratory cycle, while the patient is sleeping, to ameliorate sleep disordered breathing;

• said patient interface comprising:
• a plenum chamber at least partially forming a cavity pressurisable to a therapeutic pressure of at least 6 cmH2O above ambient air pressure, said plenum chamber including a plenum chamber inlet port sized and structured to receive the flow of air at the therapeutic pressure for breathing by a patient;
• and
• a seal-forming structure including:
• an elastomeric membrane constructed and arranged to form a pressure-assisted seal with a region of the patient's face surrounding the entrance to the patient's airways inferior to a nasal bridge region of the patient's face, said elastomeric membrane having at least one hole such that the flow of air at said therapeutic pressure is delivered to at least the entrance to the patient's nares, the seal-forming structure constructed and arranged to maintain said therapeutic pressure in the cavity throughout the patient's respiratory cycle in use;
• wherein the elastomeric membrane includes a three-dimensional shape having multiple curvatures;
• and
• wherein the at least one hole includes an arch on a lateral side of the at least one hole, the arch is in a relaxed state prior to use, and the arch is configured to move to a substantially taut state while in use.