CRYOSURGICAL INSTRUMENT WITH VENT HOLES AND METHOD

摘要

2117081 9304647 PCTABS00020 A closed end surgical cryoprobe instrument (10) may have a probe shaft (13) diameter of 3 millimeters or less and can achieve and maintain freezing zone temperature close to that of the liquid cryogenic refrigerant. Using sub-cooled liquid nitrogen at approximately -208 ·C freezing zone (15) temperatures as low as -206 ·C can be achieved in under 1 minute. The liquid nitrogen supply tube (22) is provided with a plurality of small vent holes (29) to vent gas formed or present in the refrigerant supply tube to the return refrigerant flow channel (24). The vent holes (29) also allow small amount of liquid nitrogen to vent into the return flow channel to further reduce the temperature differential between the sub-cooled liquid nitrogen supply and the counter current flowing return refrigerant. Heat transfer is maintained through nucleate boiling.