A tracheostomy tube (1) has a movable and lockable flange (2) by which the tube can be supported about the neck of a patient. The flange has a rotatable locking ring (34), which is threaded with a housing (26) fixed with the wings (22 and 23) of the flange. A resilient sleeve (50) is located in a recess (44) of the locking ring between a compression surface (45) on the locking ring at one end and the floor (46) of the housing at the opposite end. When the locking ring (34) is twisted it is moved forwardly along the housing (26), thereby compressing the resilient sleeve (50) axially. The axial compression causes the sleeve (50) to expand radially against the outside of the tube (1) and the inside of the housing (26), thereby locking the flange (2) in position.
