Medical device with enhanced cooling power

A medical device comprising:

• a first member defining an injection lumen therein, the first member having a proximal end, an open distal end, and at least one aperture proximate the distal end,
• a second member disposed around the first member, defining a cooling lumen therebetween, and
• a third member disposed around the second member, the third member having a thermally transmissive distal end portion, the thermally transmissive distal end portion defining an expansion chamber proximate the distal end of the first member, the expansion chamber defining a fluid path for the flow of cryogenic fluid;
• wherein the distal end portion of the second member is closed;
• and
• wherein the third member defines a return lumen therebetween;
• the injection lumen, the at least one aperture, and the cooling lumen defining a first fluid path;
• the injection lumen, the open distal end, and the return lumen defining a second fluid path.

A medical device comprising:

• a first member defining an injection lumen therein, the first member having a proximal end, an open distal end, and at least one aperture proximate the distal end,
• a supply of cryogenic fluid in fluid communication with the injection lumen, the cryogenic fluid further comprising nitrous oxide,
• a second member disposed around the first member, defining a cooling lumen therebetween, the second member further comprising a closed distal end portion, the distal end portion being coupled to the distal end of the first member proximate the at least one aperture of the first member, and
• a third member disposed around the second member, the third member defining a return lumen therebetween, the third member further comprising a thermally transmissive distal end portion;
• the injection lumen, the at least one aperture, and the cooling lumen defining a first fluid path;
• the injection lumen, the open distal end, and the return lumen defining a second fluid path.