Fluid cassette with tensioned polymeric membranes for patient heat exchange system

Abstract

A working fluid cassette for an intravascular heat exchange catheter includes a frame holding two closely spaced, square polymeric membranes in tension. Working fluid from the catheter is directed between the membranes. The cassette is closely received between two refrigerant cold plates to exchange heat with the working fluid, which is circulated back to the catheter.

What is claimed is: 
     
         1 . Device, comprising:
 a frame defining a periphery and an opening bounded on at least three sides by the periphery, the frame being configured for being closely received between two cold plates, the frame having at least a fluid inlet and a fluid outlet both establishing respective fluid passageways through the frame into the opening, the fluid inlet and outlet being configured for fluid communication with respective fluid return and supply lines associated with a patient-engageable heat exchange member; and   a polymeric membrane assembly connected to the frame and blocking the opening, the membrane assembly including a first membrane parallel to a second membrane with a space therebetween, the fluid inlet and fluid outlet communicating with the space between the membranes, at least one of the membranes being disposed in tension in the opening.   
     
     
         2 . The device of  claim 1 , wherein the heat exchange member includes an intravascular heat exchange catheter. 
     
     
         3 . The device of  claim 1 , wherein the heat exchange member includes a heat exchange pad externally engageable with a patient. 
     
     
         4 . The device of  claim 1 , wherein the space is expandable when filled with working fluid circulating from the heat exchange member. 
     
     
         5 . The device of  claim 1 , wherein each membrane is no more than two mils (0.002″) thick. 
     
     
         6 . The device of  claim 1 , wherein the membranes are disposed in biaxial tension in the frame. 
     
     
         7 . The device of  claim 1 , wherein the opening is rectilinear. 
     
     
         8 . The device of  claim 7 , wherein the opening defines a top, a bottom edge spaced from and parallel to the top, a left side extending between the top and bottom, and a right side extending between the top and bottom and parallel to the left side, the left and right sides defining a first length, the top and bottom defining a second length, the first length being equal to the second length±ten percent of the second length. 
     
     
         9 . The device of  claim 8 , wherein the first length is approximately equal to the second length. 
     
     
         10 . The device of  claim 1 , wherein both membranes of the membrane assembly are disposed in tension within the opening. 
     
     
         11 . The device of  claim 10 , comprising plural posts on the frame, at least portions of the membrane assembly being stretched over the posts and being engaged with the posts to hold the membrane assembly in tension within the opening. 
     
     
         12 . The device of  claim 1 , wherein the membrane assembly defines a rectilinear border juxtaposed with the frame, the border including the first and second membranes and at least one reinforcing layer engaged with the first and second membranes to at least in part establish the border. 
     
     
         13 . The device of  claim 1 , wherein the membranes are stretchable to at least 25% elongation. 
     
     
         14 . The device of  claim 1 , comprising the cold plates. 
     
     
         15 . The device of  claim 14 , comprising the heat exchange member. 
     
     
         16 . Apparatus comprising:
 working fluid chamber defined by two and only two membranes closely spaced from each other; and   a hollow frame bordering at least portions of the working fluid chamber and holding the membranes in biaxial tension, the hollow frame defining at least one fluid passageway through which fluid can pass into and/or out of the working fluid chamber, wherein when the apparatus is disposed between heat exchange surfaces of a heat exchanger and working fluid fills the working fluid chamber, the working fluid chamber expands against the heat exchange surfaces to facilitate heat exchange with the working fluid.   
     
     
         17 . The apparatus of  claim 16 , wherein the frame is substantially square and the membranes are polymeric membranes each being no more than two mils (0.002″) thick. 
     
     
         18 . The apparatus of  claim 16 , comprising plural posts on the frame, at least portions of the membranes being stretched over the posts and being engaged with the posts to hold the membranes in tension within the opening. 
     
     
         19 . The apparatus of  claim 16 , wherein the membranes define a rectilinear border juxtaposed with the frame, the border including the first and second membranes and at least one reinforcing layer engaged with the first and second membranes and not extending radially inwardly past the border. 
     
     
         20 . Method comprising:
 stretching first and second polymeric membranes over supports on a first frame half; and   engaging the first frame half with a second frame half to establish a cassette receivable between two cold plates, the frame having fluid passageways into a space between the membranes such that the frame is configured for fluid communication with fluid return and supply lines associated with a patient-engageable heat exchange member.