| 摘要 |
Cannulas for surgical and medical use expand along their entire lengths. The cannulas are inserted through tissue when in an unexpanded condition and with a small diameter. The cannulas are then expanded radially outwardly to give a full-size instrument passage. Expansion of the cannulas occurs against the viscoelastic resistance of the surrounding tissue. The expandable cannulas do not require a full depth incision, or at most require only a needle-size entrance opening. In one embodiment of the invention, the cannula has a pointed end portion. In this embodiment of the invention, the cannula includes wires having cores which are enclosed by jackets. The jackets are integrally formed as one piece with a sheath of the cannula. The cannula may be expanded by inserting members or by fluid pressure. The cannula is advantageously utilized to expand a vessel, such as a blood vessel. An expandable chamber may be provided at the distal end of the cannula.
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