Human sperm cryobanking: Use of modified liquid nitrogen vapor

OBJECTIVE: To study a modified liquid nitrogen vapor cryopreservation technique for human spermatozoa. STUDY DESIGN: The freezing rate of the modified liquid nitrogen vapor method was controlled using thermocouple probes to simultaneously measure the temperature of both the liquid nitrogen vapor and semen specimen. Sperm cryosurvival and postthaw velocity were compared using a programmable biologic freezer and our modified vapor freezing procedure. RESULTS: There were no significant differences in postthaw sperm viability between the two methods. CONCLUSION: This modified vapor freezing technique permits controlled cooling that is efficient, rapid and inexpensive.