Plastics-coated metal cannula for inserting into blood vessels - has bare tip, and constriction to render coating coplanar with metal tube for smooth insertion

摘要

Metal cannula adapted to be introduced into a blood vessel is sheathed almost as far as its obliquely cut tip, with a plastics catheter or cannula. Close to its tip, the metal cannula has a constriction where the plastics sheathing terminate in such a way that ehri surface is flush with the adjacent, unsheathed, tip of the metal cannula. Downstream of the constriction i.e. nearer the tip, the dia. of the metal cannula widens conically to its dia. upstream of the constriction. The latter is suitably formed by a rounded or slanting step.