ABSTRACT
OBJECTIVE: To compare the effects of cryopreserved sperm in vapor and liquid phases of liquid nitrogen on sperm motility, morphology, and sperm function. DESIGN: Experimental study. SETTING: Andrology laboratory at Ramathibodi Hospital, Thailand. PATIENT(S): Thirty-eight semen samples with normal motility and sperm count were collected from 38 men who were either patients of an infertility clinic or had donated sperm for research. INTERVENTION(S): Each semen sample was divided into two aliquots. Samples were frozen with static-phase vapor cooling. One aliquot was plunged into liquid nitrogen (-196 degrees C), and the other was stored in vapor-phase nitrogen (-179 degrees C) for 3 days. Thawing was performed at room temperature. MAIN OUTCOME MEASURE(S): Motility was determined by using computer-assisted semen analysis, sperm morphology was determined by using eosin-methylene blue staining, and sperm function was determined by using a hemizona binding test. RESULT(S): Most of the motility parameters of sperm stored in the vapor phase were not significantly different from those stored in the liquid phase of liquid nitrogen, except in amplitude of lateral head displacement. The percentages of normal sperm morphology in both vapor and liquid phases also were not significantly different. There was no significant difference in the number of bound sperm in hemizona between sperm cryopreserved in both vapor and liquid phases of liquid nitrogen. CONCLUSION(S): Cryopreservation of human sperm in a vapor phase of liquid nitrogen was comparable to cryopreservation in a liquid phase of liquid nitrogen.
