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

To study a generalized stress reaction as well as endothelin-1 concentratio ns during moderate hyperbaria and hyperbaric oxygen (HBO2), eight professio nal divers were exposed to air (O-2 21%, AIR) and oxygen (O-2 100%, HBO2 at 2.5 atm abs for 60 min in separate sessions. Plasma concentrations of epin ephrine, norepinephrine, dihydroxyphenylglycol (metabolite of norepinephrin e), cortisol, ADH, renin, aldosterone, pro-ANP, and endothelin-1 were analy zed before, during, and 20 min after the treatments. Endothelin-l increased significantly (6% during HBO2 and 18% during AIR, and 30 and 34% after the treatments, respectively, P = 0.032). There was no statistically significa nt difference in the changes of mean norepinephrine and dihydroxyphenylglyc ol levels between the treatments, although both seemed to change slightly d uring the treatments, but not over the baseline (time effect P = 0.031 and P = 0.011, respectively). Cortisol levels decreased significantly (P = 0.00 1) during the treatments. No significant changes were found in other analyz ed hormone. The authors concluded that a) HBO, and hyperbaric air at 2.5 at m abs do not induce a generalized hormonal stress reaction, and b) endothel in-1 increases during HBO2 and hyperbaric air at 2.5 atm abs.