A cannula having at least three separate flow passages and comprising separate nasal and mouth main bodies. The nasal body has first and second nares and first and second main flow chambers respectively communicating with first and second ports, and the first and second flow chambers are separated from one another by a septum. The mouth main body is adjacent the nasal main body and has at least one mouthpiece and at least a third main flow chamber therein communicating with a third port. The cannula has at least first, second and third flow paths which can be connected with a desired supply, monitoring or detection device. The invention also relates to the method of manufacturing the cannula.