A mask assembly is provided for delivering gas to a patient that includes a mask body and a breathing circuit interface. The mask body includes an opening for reception of the gas and includes a seal structure for sealingly engaging with the face of the patient and surrounding at least the nose and mouth of the patient. The breathing circuit interface includes a first portion rotatably connected with the mask body and a second portion that is constructed and arranged to releasably connect with a conduit for delivering the gas to the patient through the opening.