Decompression sickness and bubble formation in females exposed to a simulated 7.8 psia suit environment

The purpose of this study was to measure female susceptibility to decompression sickness (DCS) during simulated extravehicular activity (EVA) at a candidate (7.8 psia) suit pressure. Thirty female volunteer subjects, in groups of three, were exposed to three consecutive daily EVA simulations at 7.8 psia (5,031 m altitude equivalent) continuously for 6 h. During each altitude exposure, the subjects breathed a gas mixture of 50% oxygen/50% nitrogen, and participated in exercise workloads similar to those expected to be experienced by astronauts during a typical EVA scenario. Precordial Doppler bubble monitoring was accomplished after each cycle of exercise workload simulations. During at least 1 of the 3 days (d) of exposure, 43% of the subjects experienced intravenous bubbling. Of the 30 subjects, 17 (57%) did not experience detectable bubbling on any of the 3 d of exposure and 5 (17%) developed decompression sickness (DCS) during the study. Two cases were delayed, occurring after recompression to ground level; and three subjects required hyperbaric oxygen treatment. The results of this study suggest that female subjects may suffer more delayed DCS symptoms, necessitating hyperbaric oxygen treatment, than their male counterparts under the same experimental conditions. Female subjects did not experience intravenous bubbling as frequently as male subjects when exposed to these study conditions.