P-271 How much should you tolerate? The tolerance level of gas mixtures percentage in premixed gases

Abstract

Abstract Study question Does the percentage of tolerance level of gas mixtures for premixed gas affect blastocyst formation rate? Summary answer A lower percentage of gas tolerance level can improve the blastocyst formation rate by providing a more optimal pH in the culture microenviroment. What is known already Benchtop incubators that use premixed gases are regarded as one of the most common incubators used in many IVF setups. The level of CO2 in the mixture has a direct impact on the media’s pH whereby an increase in the CO2 level will result in a lower pH and vice versa. Most media companies require a percentage of 6.0-6.5% to achieve an acceptable pH range of 7.2-7.4 for optimal culture microenvironment. However, it is often taken for granted that the CO2 and pH of the medium is within the acceptable range due to the “certificate” provided by these gas companies. Study design, size, duration This is a retrospective study looking at the average blastocyst formation rate from January 2018-December 2022 on 1665 cycles. Participants/materials, setting, methods The total MII collected and inseminated was 21,631. The mean women’s age was 37 ± 4.2 years old. All the embryos were cultured in the same laboratory conditions using BT 37 Planer (Origio) and K-Minc (Cook) incubators. From January 2018 to July 2020, all the patient’s embryos were cultured with premixed gas of 5% tolerance level (n = 940) and from Aug 2020-December 2022, all of the embryos were cultured with premixed gas of 2% tolerance level (n = 725). Main results and the role of chance It was found that the average blastocyst rate was significantly increased when the gas tolerance level was 2% (57.09%) when compared to when the gas tolerance level was 5% (52.11%) (p < 0.05). Limitations, reasons for caution Different gas companies may use different methods of measuring the gas percentage levels. Therefore, it is advisable to be cautious and impose internal QC on the gas mixture percentage on individual cylinders. Wider implications of the findings A lower gas tolerance level may provide a more optimal accuracy of gas percentage to achieve the desired pH for embryo culture and to improve IVF outcomes. Trial registration number not applicable