EXPANDABLE CANNULA
Cannulas for surgical and medical use expand along their 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 includes a number of arcuate plate segments movable with respect to each other for enabling an increase in cross-sectional area of the cannula lumen. In this embodiment, the cannula can be provided with a pointed end portion. 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.
1 . A method of accessing an interior portion of a body of a patient, comprising
inserting an expandable cannula into the body of the patient, the expandable cannula including a tubular sheath defining a passage extending between axially opposite end portions of the tubular sheath;
expanding the tubular sheath and passage from a first position having a first cross sectional area to a second position having a second cross sectional area, wherein the second cross sectional area is greater than the first cross sectional area; and
inserting a medical device through the passage into the interior portion of the body of the patient.
2 . The method of claim 1 , wherein inserting an expandable cannula into the body of the patient comprises:
piercing the body of the patient with a distal end of the tubular sheath; and
inserting at least a portion of the tubular sheath through the piercing.
3 . The method of claim 2 , wherein piercing the body of the patient with a distal end of the tubular sheath comprises:
inserting a trocar through the passage such that a sharpened tip of the trocar extends past the distal end of the tubular sheath; and
piercing the body of the patient with the sharpened tip of the trocar; and
removing the trocar from the expandable cannula.
4 . The method of claim 2 , wherein the distal end portion of the tubular sheath comprises a pointed end portion when the tubular sheath is in the first position.
5 . The method of claim 1 , wherein inserting an expandable cannula into the body of the patient comprises:
making an incision in the body of the patient; and
inserting at least a portion of the tubular sheath through the incision.
6 . The method of claim 1 , wherein the first cross sectional area is a first oval cross sectional area.
7 . The method of claim 1 , wherein the second cross sectional area is a second oval cross sectional area.
8 . The method of claim 1 , wherein expanding the tubular sheath and passage from a first position having a first cross sectional area to a second position having a second cross sectional area, comprises:
inserting a first longitudinal expansion member into the passage, the first longitudinal expansion member having a cross sectional area greater than the first cross sectional area, such that the passage expands from the first cross sectional area to the second cross sectional area.
9 . The method of claim 1 , further comprising expanding the tubular sheath and passage from the second position to a third position having a third cross sectional area, wherein the third cross sectional area is greater than the second cross sectional area.
10 . The method of claim 9 , wherein expanding the tubular sheath and passage from a first position having a first cross sectional area to a second position having a second cross sectional area, comprises inserting a first longitudinal expansion member into the passage, the first longitudinal expansion member having a cross sectional area greater than the first cross sectional area, such that the passage expands from the first cross sectional area to the second cross sectional area.
11 . The method of claim 10 , wherein expanding the tubular sheath and passage from the second position to a third position having a third cross sectional area, comprises:
inserting a second longitudinal expansion member into the passage, the second longitudinal expansion member having a third cross sectional area greater than the second cross sectional area, such that the passage expands from the second cross sectional area to the third cross sectional area; and
removing the first longitudinal expansion member.
12 . The method of claim 11 , wherein removing the first longitudinal expansion member comprises:
removing the first longitudinal expansion member prior to inserting the second longitudinal expansion member, such that the passage radially contracts.
13 . The method of claim 12 , further comprising allowing tissue surrounding the tubular sheath to relax prior to removing the first longitudinal expansion member.
14 . The method of claim 1 , further comprising removing the tubular sheath.
15 . The method of claim 1 , wherein the tubular sheath is resiliently expandable.
16 . The method of claim 1 , wherein the medical device has a cross sectional area greater than the first cross sectional area of the passage in the first position.
17 . A method of accessing an interior portion of a body of a patient, comprising:
piercing the body of the patient with a distal end portion of an expandable cannula, the expandable cannula including a tubular sheath defining a passage extending between a proximal end portion and the distal end portion of the tubular sheath;
inserting at least a portion of the tubular sheath through the piercing; and
expanding the tubular sheath and passage from a first position having a first cross sectional area to a second position having a second cross sectional area greater than the first cross sectional area, wherein the distal end portion of the tubular sheath includes a pointed end portion when the tubular sheath in is the first position.
18 . A method of accessing an interior portion of a body of a patient, comprising:
inserting an expandable cannula into the body of the patient, the expandable cannula including a tubular sheath defining a passage extending between axially opposite end portions of the tubular sheath; and
expanding the tubular sheath and passage from a first position having a first oval cross sectional area to a second position having a second oval cross sectional area, wherein the second oval cross sectional area is greater than the first oval cross sectional area.