Hormonal changes during decompression sickness

Changes in plasma hormone levels were studied in anesthetized dogs during decompression sickness. Hormone levels were measured in 4 groups: control (no dive, n = 9); air group (air dive, ventilated with air postdive, n = 6); helium-oxygen (He-O2) group (air dive, ventilation changed to He-O2 at 30 min postdive, n = 9); nonsurvivor group (air dive, died within 30 min postdive, n = 9). Dived animals were subjected to repetitive dives until pulmonary artery pressure doubled. Plasma epinephrine (Epi) and norepinephrine (NE) concentrations rapidly increased postdive in all animals. Serum angiotensin-converting enzyme (ACE) activity increased postdive in the He-O2 group only, and these increases were small. Diving did not alter serum concentrations of cortisol, thyroxine (T4), or triiodothyronine (T3); however, T4 and T3 fell in all animals, probably as a consequence of anesthesia. He-O2 breathing did not affect concentrations of Epi, NE, cortisol, T4, T3, or serum ACE activity.