影响胚胎培养液pH及CO2平衡的因素探讨

目的探讨胚胎培养液在CO2平衡及使用过程中pH的动态变化特性。方法应用血气分析仪检测人输卵管液（HTF）培养液在CO2平衡过程中不同时间、CO2浓度、液量、加油厚度以及失去CO2支持后的二氧化碳分压（PCO2）和pH的变化。结果胚胎培养液添加10％合成血清代用品（SSS）后，HCO3^-]降低2．19mmol／L，pH降低0．022.1．0ml培养液CO2完全平衡时间为5h，加油后延长至15h，培养液经5．0％CO2完全平衡的最终pH为7．270-7．280。培养液液面越高平衡效果越差，≥6．0ml培养液CO2平衡15h后pH尚未稳定。CO2浓度由5．0％提高到6．0％，培养液pH降低0．060。培养液加油越厚其平衡效果越差，矿物油预先经过CO2平衡能明显提高平衡效果。失去CO：支持的无油培养液在静止状况下pH稳定时间为23min，而加油培养液的pH稳定时间超过60min。结论胚胎培养液CO2平衡宜采用适量多管和≥15h的过夜平衡方法；失去CO2支持的无油平衡培养液的操作时间应尽量短，而加油培养液可稍延长；应尽量减少培养液的加油厚度，使用预先CO2平衡的矿物油能明显提高平衡效果；应实测培养液pH来客观评价CO2平衡效果或CO2气体质量，选择适宜的CO2气体浓度、平衡方式和平衡时间。

Investigation on the factors affecting pH and carbon dioxide balance of embryo culture medium

Objective. To investigate the dynamic changes of pH and partial pressure of carbon dioxide （PCO2） during the carbon dioxide （CO2） balance of embryo culture medium. Methods.. PCO2 and pH of human tubal fluid （HTF） medium were detected by a blood-gas analyzer during CO2 balance at different time points, different concentrations of CO2, different volumes of medium, different heights of mineral oil or after no CO2 supplied. Results. The addition of 10% SSS into HTF medium resulted in a decrease of 2. 19 mmol/L in concentration of HCO3 and a decrease of 0. 022 in pH value; The duration of complete CO2 balance was 5 hours for 1.0ml medium without mineral oil but 15 hours for the medium with mineral oil; The pH values of completely balanced medium ranged from 7. 270 to 7. 280. The larger the medium volume was, the worse the balance result was. When the medium volume was larger than 6 ml, the pH was still unstable after 15 hours. The pH value was higher at the upper portion than at the bottom of the same medium; Increasing CO2 concentration from 5.0% to 6.00//00 resulted in a decrease of 0. 060 in pH value; The height of the covered mineral oil was positively correlated with pH value （P〈0. 001）, but pre-balance of the mineral oil with CO2 could achieve a better balance result of culture medium; Without CO2 supplied, pH remained relatively stable in 20 minutes in the medium without covered mineral oil, but was still relatively stable after 60 minutes in the medium with covered mineral oil. Conclusions： The embryo culture medium to be balanced with CO2 should be made into multiple aliquots and the balance time should be more than 15 hours. The manipulation time outside the incubator should be less than 15 minutes if the culture medium without oil covered. The height of mineral oil covering on the medium should be reduced and the pre-balance of the mineral oil with CO2 could improve the balance result significantly. The best concentration of CO2, the best methods of balance and the most suitable time should be determined according to the pH value detected.