Cryosurgical instrument

A cryosurgical instrument for use with a remote source of pressurized gas and adapted to operate in a cooling mode and in a rapid warming or defrost mode, comprising:

• a body having a wall of high thermal conductivity defining an enclosed cavity, said wall being shaped externally for contacting human tissue and providing heat transfer with the tissue and being of sufficient structural integrity to withstand the full force of a pressurized gas;
• a first conduit extending through said body and terminating adjacent said cavity for metering a pressurized gas therethrough so that said gas may expand into said cavity and undergo an isoenthalpic or Joule-Thomson expansion and in so doing cool said wall;
• a second conduit terminating in said cavity;
• an exhaust passage leading from said cavity to atmosphere;
• and
• first valve means for providing a cooling mode gas flow path from a source of pressurized gas, through said first conduit into said cavity and then through said exhaust passage, whereby the expansion of gas through said first conduit cools said wall, and for selectively providing a rapid warming or defrost mode gas flow path from said source of pressurized gas through said second conduit directly to said cavity for pressurizing said cavity sufficiently to condense said gas on the cool wall and liberate latent heat to warm the wall, and
• continuously open second valve means between said cavity and exhaust passage for selectively back pressuring said cavity during said cooling and rapid warming or defrost mode so that during said cooling mode there is insufficient back pressure on said gas continuously flowing through said cavity to cause the same to condense therein while during said rapid warming or defrost mode, there is sufficient back pressure on said gas to cause the same to condense and give up its latent heat of vaporization to said body enclosing said cavity to warm said body while allowing said gas to be continuously discharged from said instrument prior to reinstitution of said cooling mode.