A cannula was a length of flexible tubing that provided life-sustaining substances to patients.
In 1944, Crewman Daniels wore a cannula while dying. (ENT: "Storm Front, Part II")
In 1986, a kidney patient at Mercy Hospital had a nasal cannula. (Star Trek IV: The Voyage Home)
In 2153, a comatose Trip Tucker wore a cannula in Enterprise NX-01's sickbay. (ENT: "Similitude")