Nested balloon cryotherapy

Abstract

A cryotherapy system includes a cryotherapy catheter having an inflatable balloon portion and a pressure regulator. The inflatable balloon portion includes an outer balloon and an inner balloon within the outer balloon. The inner balloon is configured to receive during a cryotherapy procedure a cryogenic agent for extracting heat from body tissue at a desired location. The inflatable balloon portion is at a distal end of the cryotherapy catheter. The pressure regulator is adapted to maintain a positive pressure between the inner balloon and the outer balloon during a cryotherapy procedure.

We claim: 
     
         1 . A cryotherapy system comprising:
 a cryotherapy catheter including an inflatable balloon portion at a distal end of the cryotherapy catheter, the inflatable balloon portion including:
 an outer balloon; and 
 an inner balloon within the outer balloon, the inner balloon configured to receive a cryogenic agent during a cryotherapy procedure for extracting heat from body tissue at a desired location; 
   wherein the system is configured to maintain a positive pressure between the inner balloon and the outer balloon sufficient to maintain a fluid space between the inner balloon and the outer balloon during the cryotherapy procedure.   
     
     
         2 . The cryotherapy system of  claim 1 , further comprising a detector configured to monitor the pressure between the inner balloon and the outer balloon and to determine whether a leak of the inner or outer balloon has occurred. 
     
     
         3 . The cryotherapy system of  claim 1 , further including a pressure regulator configured to maintain the positive pressure between the inner balloon and the outer balloon sufficient to maintain the fluid space between the inner balloon and the outer balloon when the outer balloon is within a body lumen. 
     
     
         4 . The cryotherapy system of  claim 3 , wherein the pressure regulator is configured to maintain the positive pressure at between 0.1 and 2 psi greater than blood pressure. 
     
     
         5 . The cryotherapy system of  claim 3 , wherein the pressure regulator includes a valve, the pressure regulator configured to maintain the positive pressure by closing the valve once the space between the outer balloon and the inner balloon is filled with a predetermined amount of fluid. 
     
     
         6 . The cryotherapy system of  claim 1 , wherein the outer balloon is more compliant than the inner balloon. 
     
     
         7 . The cryotherapy system of  claim 1 , wherein the outer balloon includes a material selected from the group consisting of urethane, polyether block amide, and combinations thereof. 
     
     
         8 . The cryotherapy system of  claim 1 , wherein the outer balloon includes a wall, the wall including a plurality of compressible structures, wherein compression of the compressible structures reduces an insulating property of the wall. 
     
     
         9 . The cryotherapy system of  claim 9 , wherein the plurality of compressible structures are selected from the group consisting of air pockets, liquid pockets, gel pockets, dimples, open cell foam, and combinations thereof. 
     
     
         10 . A method of performing a cryotherapy procedure, the method comprising:
 delivering a distal end of a cryotherapy catheter to a desired anatomical location, the distal end including an inflatable balloon portion including an outer balloon and an inner balloon within the outer balloon;   inflating a space between the outer balloon and the inner balloon with an insulating fluid;   inflating the inner balloon with a cryogenic agent;   maintaining a positive pressure of the insulating fluid within the space between the outer balloon and the inner balloon to maintain a spacing between the inner balloon and the outer balloon;   pressing the inflatable balloon portion against a target tissue region with sufficient force to deform the outer balloon and overcome the positive pressure of the insulating fluid within the space between the outer balloon and the inner balloon until the inner balloon is in contact with a portion of the outer balloon pressing against the target tissue region.   
     
     
         11 . The method of  claim 10 , further including monitoring the positive pressure of the insulating fluid within the space between the outer balloon and the inner balloon to determine whether a leak of the inner balloon or the outer balloon has occurred. 
     
     
         12 . The method of  claim 10 , wherein the positive pressure of the insulating fluid within the space between the outer balloon and the inner balloon is maintained at between 0.1 and 2 psi greater than a blood pressure. 
     
     
         13 . The method of  claim 10 , further including retracting the distal end of the cryotherapy catheter from the desired anatomical location, retracting including:
 deflating the inner balloon while maintaining the positive pressure of the insulating fluid within the space between the outer balloon and the inner balloon;   releasing the positive pressure of the insulating fluid within the space between the outer balloon and the inner balloon to fully deflate the inflatable balloon portion; and   removing the deflated inflatable balloon portion from the desired anatomical location.   
     
     
         14 . The method of  claim 10 , wherein the insulating fluid is selected from the group consisting of: nitrogen, oxygen, argon, carbon dioxide, nitrous oxide, helium, krypton, sugar solutions, saline solutions, polyols, glycols, dimethyl sulfoxide, and mixtures thereof. 
     
     
         15 . The method of  claim 10 , wherein the cryogenic agent is select from the group consisting of: nitrogen, nitrous oxide, carbon dioxide, methane, ethane, butane, propane, chlorofluorocarbons, hydrochlorofluorocarbons, and mixtures thereof. 
     
     
         16 . The method of  claim 10 , wherein maintaining the positive pressure of the insulating fluid within the space between the outer balloon and the inner balloon includes closing a valve once the space between the outer balloon and the inner balloon is filled with a predetermined amount of fluid. 
     
     
         17 . The method of  claim 10 , wherein the outer balloon includes a wall defining a plurality of compressible structures, and pressing the inflatable balloon portion against the target tissue region compresses at least one of the plurality of compressible structures, reducing an insulating property of the wall. 
     
     
         18 . The method of  claim 17 , wherein the plurality of compressible structures are selected from the group consisting of air pockets, liquid pockets, gel pockets, dimples, open cell foam, and combinations thereof. 
     
     
         19 . The method of  claim 17 , wherein the plurality of compressible structures includes pockets filled with a fluid. 
     
     
         20 . The method of  claim 19 , wherein the fluid is an insulating fluid.