A patient interface to provide breathable gas to a patient, comprising: a plenum chamber assembly, comprising: a nasal plenum chamber at least partly defining an upper gas chamber; an oral plenum chamber at least partly defining a lower gas chamber; and a decoupling structure at least partly connecting the nasal plenum chamber and the oral plenum chamber and at least party defining a flow path; a top plate including at least one connection feature configured to releasably retain a first portion of a positioning and stabilising structure; and a faceplate configured to releasably retain a second portion of a positioning and stabilising structure.