Source:http://linkedlifedata.com/resource/umls/id/C0179580
UMD: Cannulae that are internal independent components of a metallic or plastic tracheostomy tube; they are intended to keep the stoma clear. Inner cannulae are typically small plastic tubes that are inserted into a tracheostomy tube; the cannula usually includes a lock to prevent device expulsion by coughing. Tracheostomy internal cannulae may be intended either for reuse (device must be pulled out and cleaned before reinsertion, typically 3 or 4 times per day) or for single use (i.e., disposable cannulae).