[abstract] UW SHEEP DISSUB TRIALS: OXYGEN PRE-BREATHE BEFORE DROP-OUT DECOMPRESSION OFFERS A POTENTIAL SURVIVAL BENEFIT.

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[abstract] UW SHEEP DISSUB TRIALS: OXYGEN PRE-BREATHE BEFORE DROP-OUT DECOMPRESSION OFFERS A POTENTIAL SURVIVAL BENEFIT.

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Title: [abstract] UW SHEEP DISSUB TRIALS: OXYGEN PRE-BREATHE BEFORE DROP-OUT DECOMPRESSION OFFERS A POTENTIAL SURVIVAL BENEFIT.
Author: Lehner, CE; Sobakin, AS; Abraham, JL; Dueland, RT; Wilson, MA; Gendron-Fitzpatrick, AP; Crump, PM; Keuler, NS
Abstract: BACKGROUND: In submarine rescue, disabled submarine (DISSUB) personnel may experience prolonged increased ambient pressure and abrupt emergency decompression when exiting to the surface. Scientific, recreational and operational scuba divers experiencing a saturation hyperbaric exposure and emergency decompression face similar decompression risks. We used the UW sheep model to test human “drop-out” risk of a 24-h exposure at 60 fsw (2.79 atm abs) and abrupt decompression. Would even a brief O2 pre-breathe before drop-out decompression increase survival and reduce decompression sickness (DCS) risk in emergency decompression? MATERIALS AND METHODS: We investigated the efficacy of O2 pre-breathes (15-min to 120-min) for minimizing decompression risk in adult sheep. Decompression findings were analyzed by logistic regression. All 18 ewes (85-127 kg ±10.85 SD) underwent air exposure at 60 fsw for 24-h and 14 inspired an O2 (88-92%) pre-breathe (15 min, 1-h, or 2-h) before drop-out decompression (30 fsw/min) to surface pressure. Approximately 5-6 weeks after drop-out decompression, bone scans of the radii and tibiae were performed. Sheep underwent necropsy to observe gross pathology. RESULTS: Twelve out of 18 sheep survived drop-out decompression; all 4 sheep breathing only air died of fulminant chokes, a respiratory DCS (RDCS), with pulmonary edema. Surviving sheep with O2 pre-breathes all showed frank limb bends and most developed dysbaric osteonecrosis (DON); two showed CNS-DCS. Gross pathology confirmed bone scan DON lesions. Logistic regression showed a significant relationship between survival and O2 pre-breathe duration (p =0.045) concomitant with decreasing RDCS severity. The odds of survival were 25 times higher for each hour increase in O2 pre-breathes. CONCLUSIONS: This study suggests that O2 pre-breathes can greatly reduce DCS morbidity/mortality risk in provocatively decompressed submariners and divers. (Research was funded by the U.S. Navy and UW Sea Grant Institute. We acknowledge the assistance of Ed Flynn, Bruce Wienke, Jim McCarthy and Jim Schwarz.)
Description: Abstract of the Undersea and Hyperbaric Medical Society, Inc. Annual Scientific Meeting held June 14-16, 2007. Ritz-Carlton Kapalua Maui, Hawaii (http:www.uhms.org)
URI: http://archive.rubicon-foundation.org/5146
Date: 2007

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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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