FIG. 3.

Controlled-rate cooling rates and resulting post-thaw motility can be reproduced with dry ice in two types of cryogenic vials. (A) Dark gray bars: post-thaw motility (mean ± SD) of sperm frozen in 0.5-mL matrix vials in a CRF. Cooling rates ranged from 5 to 35°C/min. An ordinary post hoc one-way ANOVA was performed using Tukey's multiple test to compare the mean of each column against every other column. The optimal cooling rate was identified as 10 to 15°C/min (labeled a). At these freeze rates, post-thaw motility was 74% ± 10% and 76% ± 5% (respectively, each n = 9), and these averages were not significantly different (p = 0.9998). However, all average post-thaw motilities of sperm frozen at rates of 5°C/min and between 20 and 35°C/min were significantly different (and lower). Light gray bars: post-thaw motility of sperm frozen in dry ice using 0.5-mL matrix vials (−14.1°C/min; 81% ± 2% motility, n = 9) and 2-mL Corning cryovials (−16.1°C/min; 74% ± 4% motility, n = 9). (B) Dry ice freezing vial assemblies. Cryogenic vial with sperm sample is placed in a 15-mL conical tube on top of an empty spacer vial of the same kind. (Left) 0.5-mL Matrix sample vial on top of an empty spacer Matrix vial with cap. (Right) 2-mL Corning cryogenic vials on top of an empty 2-mL spacer vial without cap. CRF, controlled-rate freezer; SD, standard deviation.