title: The effect of extended O2 prebreathing on altitude decompression sickness and venous gas bubbles.
abstract: The purpose of this study was to determine the effect of extended O2 prebreathing on symptom and bubble incidence during decompressions simulating extravehicular activity. The 38 subjects breathed O2 for a 6-h period prior to decompression to 4.3 psi. The subjects performed upper body exercise for 6 h. Subjects were monitored with a Doppler bubble detector and were encouraged to report all symptoms. Eight subjects were exposed to the same protocol after an 8-h prebreathe. Venous bubbles were detected in 18 of 38 subjects decompressed after the 6-h prebreathe. Four of these subjects reported symptoms of altitude decompression sickness. No symptoms or bubbles were detected in the eight subjects who had prebreathed 8 h. The incidence of symptoms and bubbles when combined with prior data on 3.5- and 4.0-hour prebreathes showed an inverse correlation to pre-breathing time. The incidence of symptoms was higher than has been reported for subjects exposed to decompression of shorter duration with less activity.
mesh_terms: D000328:Adult; D000531:Altitude; D003664:Decompression; D003665:Decompression Sickness / Q000517:prevention & control*; D005260:Female; D006801:Humans; D008297:Male; D010102:Oxygen Inhalation Therapy; D005082:Physical Exertion; D012212:Rheology; D013026:Space Flight; D013997:Time Factors