A medical mouthpiece may include a U-shaped first member having a tubular portion, the first member forming at least one lateral interocclusal passageway extending through the first member, and a second member received within the tubular portion. A medical breathing apparatus may include a U-shaped first member forming left and right lateral interocclusal passageways extending through the first member, a second member attached to the first member, and an adapter receivable within a tubular portion of the first member, wherein the adapter includes a respiratory orifice configured to deliver respiratory gas to the left and right lateral interocclusal passageways. A method for delivering positive pressure and/or a respiratory gas to a patient may include inserting a mouthpiece into a mouth of the patient, and delivering the positive pressure and/or the respiratory gas through the mouthpiece to a space adjacent a posterior oropharynx of the patient.