The invention concerns a tracheostomy tube assembly for insertion into the trachea of a patient to support breathing, said assembly comprising an outer cannula (1) having a distal end (10) and a first connector end (11) with first connector means; an insertion member (2, 3) for insertion into the outer cannula (1) and a second connector end (21, 31) provided with second connector means, said second connector means cooperating with said first connector means for locking said insertion member (2, 3) in the outer cannula (1); wherein a swivel locking member (4) is retained on the second connector end (21, 31) of the insertion member (2, 3) so that the swivel locking member (4) extend around a portion of the first connector end (11), and said lock member (4) being provided with internal engagement means (40, 41), which is adapted to cooperate with corresponding first engagement means (42, 43) provided on the external surface (44) of the first connector end (11).