Manipulating Frequency or Duration of Air Breaks During Oxygen Decompression Did Not Reveal a Direct Contribution of Oxygen to Decompression Stress

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Abstract:

Oxygen is breathed at decompression stops to enhance inert gas washout and accelerate decompression. However, there is evidence that high inspired partial pressure of oxygen can contribute to the risk of decompression sickness (DCS), presumably because oxygen can accumulate in tissues where it can contribute to bubble formation and growth and can reduce blood flow and inert gas washout. More frequent or longer air breaks than used conventionally during oxygen decompression may mitigate accumulation of oxygen in tissues, and allow oxygen breathing time to be reduced without increasing the risk of DCS. The incidence of DCS following oxygen decompression dives with conventional air breaks, longer air breaks, and more frequent air breaks were compared in a two-phase, adaptive group sequential trial. Venous gas emboli (VGE) and symptoms of oxygen toxicity were also recorded. Dry resting dives to 132 feet of sea water (fsw) equivalent air depth for 155 minutes were followed by 251 minutes of decompression stops, with oxygen breathing at 50, 40, 30,and 20 fsw. Three air break schedules were tested: cycles of 30/6, 24/12, and 12/6 (minutes oxygen/minutes air). There were differences in oxygen breathing time but no difference in decompression stop times. In phase one, 52 to 54 man-dives were conducted with each air break schedule. Two DCS occurred on each of the 24/12 and 30/6 schedules and none on the 12/6 schedule. Phase two continued comparison of the 12/6 and 30/6 schedules, and stopped at a planned interim evaluation with six DCS in 82 dives on the 12/6 schedule and two DCS in 96 dives on the 30/6 schedule. There was no difference in VGE grades between the three schedules. Fewer symptoms of oxygen toxicity followed the 12/6 schedule than the other two schedules. Unconventional air break schedules that sacrifice oxygen-breathing time for more frequent of longer air breaks did not increase the efficiency of decompression.

Author(s):
Doolette, David J. ; Gault, Keith A. ; Gerth, Wayne A.
Author Organization(s):
NAVY EXPERIMENTAL DIVING UNIT PANAMA CITY FL; OFFICE OF NAVAL RESEARCH ARLINGTON VA
Funding Organization(s):
NAVAL SEA SYSTEMS COMMAND WASHINGTON DC, WASHINGTON, DC; OFFICE OF NAVAL RESEARCH ARLINGTON VA, ARLINGTON, VA
Document Type:
Technical Report/Technical Report
Publication Date:
2017 Dec 22
Pagination:
41

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DOCUMENT & CONTEXTUAL SUMMARY

Distribution Code:
A - Approved For Public Release
Distribution Statement: Public Release.
Copyright: Not Copyrighted

RECORD

Collection: TRECMS
Subject Terms
Descriptor(s):
medical personnel, health services, two dimensional, biomedical research, decompression sickness, pain, brain, respiration disorders, frequency, divers, lower extremity, partial pressure, algorithms, blood flow, body regions, civilian personnel, hyperbaric medicine
Keyword(s):
decompression, dcs(decompression sickness), vge(venous gas emboli), po(partial pressure), 2d(two dimensional)
Subject Categories:
Behavioral and Social Sciences; Biological and Medical Sciences
Descriptor(s):
medical personnel, biomedical research, two dimensional, pain, frequency, decompression sickness, physiology, respiration, sensation, hyperbaric conditions, hyperbaric medicine, lower extremity, algorithms, chambers, decompression, measurement, partial pressure
Creation Date:
2023 Nov 21
Update Date:
2023 Dec 05