Change Your Lab’s Thinking About Media Prep- Monitor Large Format Incubator pH

A lab has 5 patients worth of egg retrievals that all plan to culture to blastocyst stage. The embryologist prepares changeover dishes for patient 4 at 15:00 hours due to time constraints. Some culture dishes are placed in the benchtop incubator, and some dishes are placed in the large format incubator, as not all of the dishes fit in the benchtop incubator. The next day, frequent opening and closing of the large format incubator occurs from the start of day QC checks and culture dish removal/replacements for other patients. Patient 4 has their fertilization check and changeover at approximately 08:00 during this frequent incubator usage.

The lab has no data to determine how long it takes for culture dish pH to stabilize in the large format incubator. Patient 4’s dishes equilibrated for 17 hours, but some dish prep setups can take as long as 24 hours to equilibrate (Figure 1). If the media pH is not equilibrated, the pH in Patient 4’s dishes will continue to decrease with the embryos in it. The lab currently has no way of knowing if their dishes are truly equilibrated and cannot observe the potential effects on embryo development.

Shocks from rapid changes in pH should be minimized during embryo development. Frequent usage of the large format incubator can cause fluctuations in media pH, including in dishes and through the oil overlay (Figure 2). This fluctuation causes the dishes for patient 4 and any other patient to differ in pH conditions compared to their benchtop incubator siblings.

Equipment differences between the large format incubator and the benchtop incubators can cause differences in media pH values. CO₂ overshoot (Figure 3), water pan levels (Figure 4), and true microdrop temperature (Figure 5) can all affect the pH found in patient 4’s culture dishes and will cause differences in pH compared to the benchtop incubator dishes.