A method of forming a cannula by forming a cannula mandrel assembly having a nare mandrel, a main body mandrel and mouthpiece mandrel heating the cannula mandrel assembly, applying a polymeric material to the cannula mandrel assembly to provide a desired material thickness on the mandrel assembly to form the cannula, curing the polymeric material of the formed cannula and extracting the mandrel assembly from the cannula by disassembly and removal of the mandrel assembly parts.