A coupling is taught for connecting the machine end 4 of a tracheostomy tube 1 to a gas coupling. The coupling arrangement requiring that the machine end 4 of the tracheostomy tube 1 have a magnet 18, 19, that is arranged to attract and retain a cooperating magnet 28, 29 on the gas coupling. The coupling arrangement also comprises a mechanical advantage to separate the coupling from the tube and overcome the magnetic attraction. This could include an arrangement for rotating the coupling relative to the tube - preferably through the provision of a bayonet type coupling (Fig 2), complementary threads (76, Fig 6) etc. - or through the provision of wedge devices (55, 56, Fig 5) that can be squeezed together between the magnets on the tube and coupling to separate them.
