Brubakk, Alf O.

Diving under cold conditions may add an additional risk for bubble production and decompression sickness. Additionally, there is sparse information regarding hemodynamic changes occurring during a dive and its effects on the outcome of a dive. Thus, detailed recordings of cardiovascular changes at different core temperatures during diving were studied. Anesthetized rats were monitored with a pressure‐volume catheter in the left ventricle and the femoral artery. Rats were randomly assigned to be normothermic controls, to perform a dry hyberbaric dive at constant core temperature (37ºC) or a dry hyperbaric dive with a core temperature of 35ºC during decompression and the early post dive period. The rats were compressed to 600 kPa, maintained for 45 min breathing air, and decompressed linearly to the surface at a rate of 50 kPa·min −1 . Immediately after surfacing, right ventricle and pulmonary artery were insonated for bubble detection using ultrasound. Compression increased mean arterial pressure, pulse pressure, stroke volume, cardiac output, LV end‐systolic volume, LV end‐systolic pressure, LV dp/dt max, and total peripheral resistance in the rats. Most of these changes gradually declined and returned to baseline after decompression. However, rewarming to 37ºC after a 2ºC drop in core temperature caused a significant reduction in SV and CO, but this did not have an effect on bubble production and survival.