[abstract] DECOMPRESSION RISK DURING HIGH ALTITUDE EXPOSURE AFTER DIVING

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[abstract] DECOMPRESSION RISK DURING HIGH ALTITUDE EXPOSURE AFTER DIVING

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Title: [abstract] DECOMPRESSION RISK DURING HIGH ALTITUDE EXPOSURE AFTER DIVING
Author: Pollock, NW; Natoli, MJ; Gerth, WA; Thalmann, ED; Vann, RD
Abstract: BACKGROUND: Post-dive altitude exposure increases the risk of decompression sickness (DCS). U.S. Special Operations (SOF) personnel may dive before conducting parachute operations at altitudes of 25,000 ft or higher. Minimum surface interval (SI) times between diving and safe flight are not known. METHODS: 102 healthy, male volunteers (34+/-10 [mean+/-SD] yrs age, 84.5+/-13.8 kg weight, 26.2+/-4.2 kg m-2 BMI) completed simulated 60 fsw/60 min air dives preceding simulated three hour flight at 25,000 ft to study DCS risk as a function of SI time. Subjects were dry and at rest throughout. Oxygen was breathed for 30 min before and during flight in accordance with SOF protocols. Subjects were monitored for clinical signs of DCS and for venous gas emboli (VGE) using precordial Doppler ultrasound. Profiles were accepted with no DCS in 23 trials (0/23), 1/35, 2/46 or 3/56. Profiles were rejected with 2 DCS cases in 10 trials, 3/26 or 4 total cases. One-way ANOVA was used to assess VGE onset and maximum VGE as a function of post-dive SI (p less than 0.05). RESULTS: Three cases of DCS occurred in 155 exposures (1.9percent): 1/35 and 0/24 in 2 h and 3 h Flight-Only controls, respectively; 0/23 for Dive-24 h SI-Flight; 1/37 for Dive-18 h SI-Flight; and 1/36 for Dive-12 h SI-Flight. Each profile was accepted with 95percent confidence that true DCS risk was =15percent. VGE were observed in 20percent of flights (Spencer Grades 3 or 4 in 8percent). Neither mean VGE onset time nor mean time to max VGE Grade differed between profiles (82+/-38 min [p=0.88] and 100+/-40 min [p=0.68], respectively). CONCLUSION: DCS risk during a resting, three-hour oxygen-breathing flight at 25,000 ft (following a 30 min oxygen prebreathe) was not significantly increased by a dry, resting 60 fsw/60 min air dive conducted 12-24 h earlier. Doppler-detectable VGE during flight were similarly unaffected. Funded by U.S. Special Operations Command ( USZA22-99-C-0002).
Description: Undersea and Hyperbaric Medical Society, Inc. (http://www.uhms.org )
URI: http://archive.rubicon-foundation.org/1168
Date: 2002

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  • UHMS Meeting Abstracts
    This is a collection of the published abstracts from the Undersea and Hyperbaric Medical Society (UHMS) annual meetings.

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