A tracheostomy tube assembly has an outer catheter and an inner cannula that is insertable into and removable from the outer catheter. The inner cannula has two elongate regions along its length of different flexibility. The main body of the cannula may be relatively stiff and a narrow region along its...http://www.google.ca/patents/US6019753?utm_source=gb-gplus-sharePatent US6019753 - Catheter assemblies and inner cannulae
