Effect of hyperbaric conditions on plasma stress hormone levels and endothelin-1

To study a generalized stress reaction as well as endothelin-1 concentrations during moderate hyperbaria and hyperbaric oxygen (HBO2), eight professional divers were exposed to air (O2 21%, AIR) and oxygen (O2 100%, HBO2) at 2.5 atm abs for 60 min in separate sessions. Plasma concentrations of epinephrine, norepinephrine, dihydroxyphenylglycol (metabolite of norepinephrine), cortisol, ADH, renin, aldosterone, pro-ANP, and endothelin-1 were analyzed before, during, and 20 min after the treatments. Endothelin-1 increased significantly (6% during HBO2 and 18% during AIR, and 30 and 34% after the treatments, respectively, P = 0.032). There was no statistically significant difference in the changes of mean norepinephrine and dihydroxyphenylglycol levels between the treatments, although both seemed to change slightly during the treatments, but not over the baseline (time effect P = 0.031 and P = 0.011, respectively). Cortisol levels decreased significantly (P = 0.001) during the treatments. No significant changes were found in other analyzed hormones. The authors concluded that a) HBO2, and hyperbaric air at 2.5 atm abs do not induce a generalized hormonal stress reaction, and b) endothelin-1 increases during HBO2 and hyperbaric air at 2.5 atm abs.