This may provide a useful insight. I have never seen or heard of a correlation between DCS hits from using hot water suits in commercial or military settings. There was considerable concern over the possibility when they were first introduced.
Obviously it is not as warm as a hot tub. Typical water temperature at the injection point of the suit (before distributing and dilution) is 110° F, which is very near the long-term level of burning skin. I understand that skin temperature is 88° F, but I really don’t know if that is the average temperature in the suit regardless of depth and mix since thermocouples are not available outside of research settings.
Many Navy hyperbaric docs of the time expressed concern that being so much warmer during the entire dive might significantly increase diluent absorption. It probably does, but apparently not enough to skew tables or decompression calculations. Conceivably, modern drysuits would also increase DCS incidents if the impact were as significant as one might guess. However, that would also hold true for warm water versus cold water diving.
It should be noted that animal and human trials were almost exclusively reasonably close to room temperature and "could" explain why the phenomenon has not shown up statistically. It may simply be that the diver being colder during the hyperbaric phase of the dive increases the safety margin rather than working against tested conditions. It is important to consider that each new generation of decompression theory is extrapolated from and tested against the existing data.
There may come a time when decompression becomes so well understood that our computers will monitor suit and breathing gas temperature but there just isn’t much data to justify it today.
