A patient interface system for delivery of a supply of breathable gas at a therapeutic pressure of at least 6cmH2O above ambient air pressure along a flow path to an entrance of a patient’s airways including at least an entrance of a patient’s nares to treat a respiratory disorder, said patient interface system comprising: a mask frame having a mask frame engagement member (3250)； a cushion assembly comprising: a seal-forming structure (3100) configured to engage the patient’s face to provide the supply of breathable gas to an entrance of the patient’s airways including at least the entrance of the patient’s nares, and a cushion assembly engagement member configured to releasably connect the seal-forming structure to the mask frame by engagement with the mask frame engagement member； a vent adaptor (3410) comprising: a vent having a plurality of holes (3400) configured to washout expiratory gas generated by the patient to atmosphere； and an inlet (3260) configured to be connected to an air circuit to receive the supply of breathable gas from a respiratory pressure therapy device； the patient interface assembly further comprising a heat and moisture exchanger (HME 7000) configured to absorb moisture from the expiratory gas and humidify the supply of breathable gas before inhalation by the patient, the HME positioned at least partly within the vent adaptor, and the HME being removable from the vent adaptor.
