Expandable cannula

Abstract

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.