A tracheostomy tube assembly includes an outer tube (1) and an inner cannula (20, 120, 220 51, 61) inserted into and removable from the tube. The inner cannula has a constant internal diameter along its length and has at its patient end (22, 122, 222) a seal member (23, 123, 223) extending around the cannula. The seal member may be a separate ring 23 of resilient material attached to the outside of the shaft of the cannula or it may be formed of the material of the shaft (121, 221) itself. Alternatively, the seal member (50, 60) may be of a kind that expands when exposed to an elevated temperature or humidity, and may include a shape memory effect material.
