HYPERBARIC-OXYGEN THERAPY INCREASES FREE-RADICAL LEVELS IN THE BLOOD OF HUMANS

It has been postulated that exposure to high concentrations of oxygen results in increased oxygen radical production which may account for t he toxic effects of excessive exposure to oxygen. Examination of blood from persons undergoing hyperbaric oxygen (HBO) exposure, by low temp erature electron spin resonance (ESR) spectroscopy, demonstrated a mar ked increase in the magnitude of a signal with properties consistent w ith a free radical (g = 2.006). The signal diminished to baseline leve ls within 10 minutes of cessation of HBO exposure. Further in vitro st udies of blood revealed an ESR signal generated in red blood cells by oxygen, and dependent on oxyhaemoglobin, which had characteristics ind istinguishable from those of the ESR signal of ascorbate radical and t he signal in blood from persons undergoing HBO exposure. It is postula ted that HBO exposure increases ascorbate radical levels in blood, whi ch is likely to reflect increased ascorbate turnover in human red bloo d cells.