Valve

Abstract

An esophageal valve has a restriction to allow antegrade passage of swallowed food and controlled retrograde passage of fluid. The restriction comprises an iris having a number of folds.

1 . An esophageal valve having a restriction to allow antegrade passage of swallowed food and controlled retrograde passage of fluid, the restriction comprising an iris having a number of folds. 
   
   
       2 . A valve as claimed in  claim 1  wherein the valve is adapted to be opened when different forces are applied in the antegrade and retrograde directions. 
   
   
       3 . A valve as claimed in  claim 2  wherein the valve is adapted to open in the antegrade direction in response to antegrade forces and to open in the retrograde direction in response to retrograde forces, the retrograde force required to open the valve being substantially greater than the antegrade force required to open the valve. 
   
   
       4 . A valve as claimed in  claim 1  wherein the iris is formed from a tubular precursor, the ends of which are oppositely rotated. 
   
   
       5 . A valve as claimed in  claim 4  wherein the precursor is folded as the ends are oppositely rotated. 
   
   
       6 . A valve as claimed in  claim 4  wherein the precursor is generally cylindrical. 
   
   
       7 . A valve as claimed in  claim 4  wherein the precursor is generally of hourglass shape. 
   
   
       8 . A valve as claimed in  claim 1  wherein the restriction comprises at least three folds. 
   
   
       9 . A valve as claimed in  claim 1  wherein the valve has means to set the differential forces required to open the valve. 
   
   
       10 . A valve as claimed in  claim 9  wherein the valve comprises a stop to restrict the opening of the valve in one direction. 
   
   
       11 . A valve as claimed in  claim 9  comprising strengthening means to restrict the opening of the valve in one direction. 
   
   
       12 . A valve as claimed in  claim 1  comprising a support for the iris. 
   
   
       13 . A valve as claimed in  claim 12  wherein the tubular iris is attached to the support. 
   
   
       14 . A valve as claimed in  claim 13  wherein a distal end of the tubular iris is attached to the support and a proximal end of the tubular iris is attached to the support. 
   
   
       15 . A valve as claimed in  claim 14  wherein the attachments are arranged such that the valve will open in response to different forces applied in the antegrade and in the retrograde directions.