Nitrogen load in rats exposed to 8 ATA from 10-35 degrees C does not influence decompression sickness risk

Environmental temperature is commonly thought to modulate decompression sickness (DCS) risk, but the literature is mixed regarding which conditions elicit the greatest risk. If temperature is a risk factor, then managing thermal exposure may reduce DCS incidence. We analyzed whether hot or cold conditions during or immediately after a hyperbaric exposure altered DCS incidence in a rat model.

Rats (eight groups of five animals in each of nine conditions; mean body mass +/- SD = 259.0 +/- 9.2 g) were placed in a dry chamber that was pressurized with air to 70 m (8 ATA) for 25 min, followed by rapid (< 30 s) decompression under a series of temperature conditions (35 degrees, 27 degrees, or 10 degrees C during compression; 35 degrees, 20 degrees, or 10 degrees C post-decompression). Animals were observed for 30 min post-decompression for signs of DCS. DCS incidence in the 27 degrees C compression/20 degrees C post-decompression group was 50% by design. Data from all nine groups of paired temperature conditions were compared with each other using analysis of variance, Chi-square tests, and logistic regression.

No significant differences in DCS incidence were found among the groups (30-52.5% DCS incidence per group, 42% DCS incidence overall).

This animal model emphasized potential temperature effects attributable to tissue N2 load acquired during compression; there was no evidence that environmental temperature from 10-35 degrees C during or post-dive modulated DCS incidence. It remains to be determined if temperature modulates DCS risk as a function of variable N2 elimination rates.