Modular patient interface including a joint coupling mouth and nasal cushions

A patient interface to deliver a flow of breathable gas at a positive pressure with respect to ambient air pressure to an entrance to a patient's airways while the patient is sleeping, to ameliorate sleep disordered breathing, the patient interface comprising:

• a mouth cushion forming at least part of a mouth cushion plenum chamber pressurizable to a therapeutic pressure,
• wherein the mouth cushion comprises a mouth seal-forming structure configured and arranged to form a seal with a region of a patient's face below the patient's nose and surrounding the entrance to the patient's mouth, a front face including a first opening and a second opening below the first opening, and a pair of lower headgear connectors attached to the front face,
• wherein the first opening is configured to allow the flow of breathable gas into and/or out of the mouth cushion plenum chamber, and
• wherein the second opening is configured to receive a removable vent;
• and
• a positioning and stabilizing structure configured to connect to the pair of lower headgear connectors and provide a force to hold the mouth seal-forming structure in a therapeutically effective position on a patient's head.