Tracheostomy tube assemblies and inner cannulae
A tracheostomy tube assembly comprises an outer tracheostomy tube ( 1 ) and an inner cannula ( 20 ) fitted in the tube. The machine end of the inner cannula has a collapsible region ( 22 ) formed by a plurality of curved or bent struts ( 26 ) extending parallel with one another between a machine end collar ( 28 ) and a patient end collar ( 27 ). The struts ( 26 ) carry outwardly-projecting catches ( 23 ) arranged to engage a rib ( 24 ) extending around the inside of a hub ( 16 ) at the machine end of the tube and thereby resist removal of the cannula from the tube. The inner cannula ( 20 ) is removed by twisting the machine end collar ( 28 ) so that the struts ( 26 ) collapse inwardly and thereby disengage the catches ( 23 ) from the rib ( 24 ).
1. An inner cannula for a tracheostomy tube, the inner cannula including a tubular shaft and a machine end region arranged to fit within a hub at a machine end of the tracheostomy tube, characterised in that an outer surface of the machine end region of the inner cannula and an inner surface of the hub on the tracheostomy tube are provided with cooperating engagement formations arranged to retain the inner cannula in the hub of the tracheostomy tube against an axial force tending to withdraw the inner cannula from the tracheostomy tube, and that the machine end region is arranged such that twisting an outer end of the machine end region about an axis of the inner cannula displaces the engagement formation on the inner cannula away from the engagement formation on the hub sufficiently to allow the inner cannula to be pulled rearwardly out of the tracheostomy tube, wherein the outer end of the machine end region is connected with a forward end of the machine end region by a collapsible region, and that the engagement formation on the machine end region is provided on the collapsible region such that twisting the outer end of the machine end region relative to the forward end causes the collapsible region to collapse inwardly and displace the engagement formation on the machine end region inwardly out of engagement with the engagement formation on the hub.
2. An inner cannula according to claim 1 , characterised in that the collapsible region is provided by a plurality of struts extending generally parallel to one another and extending generally longitudinally of the machine end region.
3. An inner cannula according to claim 2 , characterised in that the struts are curved or bent along their length.
4. An inner cannula according to claim 2 , characterised in that the struts extend forwardly from a circular machine end collar, and that the collar is formed with a plurality of grooves around its inner surface to enable the collar to buckle when twisted.
5. An inner cannula according to claim 1 , characterised in that the inner cannula includes a machine end grip having two hinged rings mounted with the machine end region of the inner cannula such that the rings can be folded together and gripped to enable the machine end region of the inner cannula to be twisted and pulled rearwardly.
6. An inner cannula according to claim 1 , characterised in that the hub has a circumference and that the engagement formation on the hub extends around only a part of the circumference of the hub and the engagement formation on the machine end region of the inner cannula such that the engagement formations on the hub and the machine end region can be displaced out of engagement by twisting the machine end region relative to the hub to enable the inner cannula to be removed from the tracheostomy tube.
7. An inner cannula according to claim 6 , characterised in that the inner cannula has at least a part of its length that is flexible about the axis of the inner cannula such that the machine end region of the inner cannula can be angularly displaced relative to a patient end of the inner cannula.
8. An inner cannula according to claim 6 , characterised in that the inner cannula has a separate rotatable component, and that the engagement formation on the inner cannula includes engagement formations provided on the rotatable component.
9. A tracheostomy tube assembly including a tracheostomy tube and an inner cannula fitted in the tracheostomy tube, wherein the inner cannula includes a tubular shaft and a machine end region fitted within a hub at a machine end of the tracheostomy tube, characterised in that an outer surface of the machine end region of the inner cannula and an inner surface of the hub on the tracheostomy tube are provided with cooperating engagement formations arranged to retain the inner cannula in the hub of the tracheostomy tube against an axial force tending to withdraw the inner cannula from the tracheostomy tube, and that the machine end region is arranged such that twisting an outer end of the machine end region about an axis of the inner cannula displaces the engagement formation on the inner cannula away from the engagement formation on the hub sufficiently to allow the inner cannula to be pulled rearwardly out of the tracheostomy tube, wherein the outer end of the machine end region is connected with a forward end of the machine end region by a collapsible region, and that the engagement formation on the machine end region is provided on the collapsible region such that twisting the outer end of the machine end region relative to the forward end causes the collapsible region to collapse inwardly and displace the engagement formation on the machine end region inwardly out of engagement with the engagement formation on the hub.