Balloon catheter

Claim 1

A method of forming a ballon catheter having a distal balloon, a catheter extending from the proximal end of said balloon forming a conduit for balloon inflation fluid, and vent means disposed at the distal end of said balloon for selectively ventinq gas above a predetermined pressure from the interior of said balloon while restricting passage of inflation fluid from said balloon, said vent means comprising a multi-winding coil extending distally from within said balloon, the interstitial spaces generally between the windings of said coil being of a predetermined small size selected to permit passage therethrough of gaseous molecules above a predetermined pressure while restricting throughpassage of larger molecules of inflation fluid, said method comprising the steps of: placing said coil over the end of a guidewire, positioning the balloon and catheter over said guidewire and coil, with said guidewire extending proximally within said catheter, said coil extending distally from within said balloon, and the distal end of said balloon disposed loosely about said coil, proximal of the distal end of said coil, surrounding the distal end of said balloon about said coil with a sleeve of silastic material pre-soaked in freon, applying radially inwardly directed pressure to the material of said balloon about said coil by causing the sleeve to dry to cause release of said freon and simultaneous shrinkage of the silastic sleeve to gather the balloon tip material closely about said coil, and applying heat to said baloon tip material to cause it to flow under uniform hoop pressure applied to said sleeve to seal about said coil, thereby fixing the distal end of said balloon to said coil in a manner whereby the distal end of said balloon catheter is permeable to gas molecules in said coil at pressure within said balloon above a predetermined level and is substantially impermeable to molecules of inflation fluid at operating pressure.

Claim 2

A method of forming a ballon catheter having a distal balloon, a catheter extending from the proximal end of said balloon forming a conduit for balloon inflation fluid, and vent means disposed at the distal end of said balloon for selectively ventinq gas above a predetermined pressure from the interior of said balloon while restricting passage of inflation fluid from said balloon, said vent means comprising a multi-winding coil extending distally from within said balloon, the interstitial spaces generally between the windings of said coil being of a predetermined small size selected to permit passage therethrough of gaseous molecules above a predetermined pressure while restricting throughpassage of larger molecules of inflation fluid, said method comprising the steps of: placing said coil over the end of a guidewire, positioning the balloon and catheter over said guidewire and coil, with said guidewire extending proximally within said catheter, said coil extending distally from within said balloon, and the distal end of said balloon disposed loosely about said coil, proximal of the distal end of said coil, surrounding the distal end of said balloon about said coil with a sleeve of silastic material pre-soaked in freon, applying radially inwardly directed pressure to the material of said balloon about said coil by causing the sleeve to dry to cause release of said freon and simultaneous shrinkage of the silastic sleeve to gather the balloon tip material closely about said coil, and applying heat to said baloon tip material to cause it to flow under uniform hoop pressure applied to said sleeve to seal about said coil, thereby fixing the distal end of said balloon to said coil in a manner whereby the distal end of said balloon catheter is permeable to gas molecules in said coil at pressure within said balloon above a predetermined level and is substantially impermeable to molecules of inflation fluid at operating pressure.