Oxidative stress during a 3.5-hour exposure to 120 kPa(a) PO2 in human divers

We examined the effect of a prolonged dive on measures of oxidative stress in human divers. Ten subjects, wearing dry suits, completed mental tasks while lying quietly at 4.6 m fresh water for 3.5 h. Subjects (9 male, 1 female) were active, experienced divers ranging in age from 19 to 54 yr. Subjects breathed an enriched air nitrox mixture yielding a P(O2) of approximately 120 kPa(a) for the duration of the dive. Venous blood was drawn before and after the dive for measurements of hemoglobin (Hb), hematocrit (Hct), plasma osmolarity (O(SM)), red blood cell osmotic fragility (Frag), superoxide dismutase activity (SODa), and thiobarbituric acid reactive substances (TBARS). Plasma volume (PV) shifts were calculated from the changes in Hb and Hct. Significant increases in Hb, Hct, Osm, Frag, and TBARS were found along with significant decreases in PV and SODa (P < or = 0.05). We conclude that hyperbaric exposures encountered by technical divers are sufficient to cause significant oxidative stress.