Comparison of cryopreserved sperm in vaporous and liquid nitrogen.

OBJECTIVE

To evaluate the feasibility of using the vaporous phase of liquid nitrogen as a storage medium for human semen samples.

STUDY DESIGN

Human semen samples were used in a 2-armed study. In the first arm, semen samples were rapidly frozen and randomly assigned to storage in either liquid nitrogen (-196 degrees C) or vapor-phase nitrogen (-189 degrees C). In the second arm, sperm specimens were frozen in a controlled, stepwise process and randomly assigned to storage in either the vaporous or liquid phase of liquid nitrogen. The samples were subsequently thawed and analyzed for sperm viability.

RESULTS

The rapid freezing technique demonstrated no differences in the examined viability parameters between semen specimens stored in either liquid or vaporous nitrogen. Similarly, semen samples prepared by the slower, controlled freezing process also showed no differences in viability parameters after storage in either the liquid or vaporous phase of liquid nitrogen. The rapid freezing technique was equal to the slow, controlled freezing method in terms of preserving the integrity of the sperm when the specimens were subsequently stored in either liquid or vaporous nitrogen.

CONCLUSION

Cryopreservation of human semen in the vapor phase of nitrogen is a viable alternative to storage in liquid-phase nitrogen.