cannula cannula a cannula (/ˈkænjʊlə/; latin meaning 'little reed'; plural cannulae or cannulas) is a tube that can be inserted into the body, often for the delivery or removal of fluid or for the gathering of samples. in simple terms, a cannula can surround the inner or outer surfaces of a trocar needle thus extending the effective needle length by at least half the length of the original needle. its size mainly ranges from 14 to 24 gauge. different-sized cannula have different colours as coded. a cannula decannulation is the permanent removal of a cannula (extubation), especially of a tracheostomy cannula, once a physician determines it is no longer needed for breathing. medicine cannulas normally come with a trocar inside. the trocar is a needle, which punctures the body in order to get into the intended space. many types of cannulas exist: intravenous cannulas are the most common in hospital use. a variety of cannulas are used to establish cardiopulmonary bypass in cardiac surgery. a nasal cannula is a piece of plastic tubing that runs under the nose and is used to administer oxygen. intravenous (iv) cannulation