A trial to determine the risk of decompression sickness after a 40 feet of sea water for 200 minute no-stop air dive.
BACKGROUND
The USN93 probabilistic model of decompression sickness (DCS) predicts a DCS risk of 3.9% after a 40 ft of seawater (fsw) for 200 min no-stop air dive, although little data is available to evaluate the accuracy of this prediction. Based on an analysis of Navy Safety Center data from diving on U.S. Navy standard air decompression tables, the observed incidence of DCS for this type of dive is 0.11%. Knowing the true incidence of the dive is important for deciding whether or not to adopt proposed probability based decompression procedures for U.S. Navy diving.


OBJECTIVE
The risk of DCS after a 40 fsw for 200 min no-stop air dive is 3.9%.


METHODS
We conducted a closed sequential trial to determine the DCS incidence on this dive.


RESULTS
Of 30 military divers who completed 91 dives, there were 2 cases of DCS (2.2%, 95% CI: 0.27 7.7%). The study was terminated early after the second DCS case because of the presence of neurological symptoms and signs.


CONCLUSIONS
This study demonstrates that the incidence of DCS in a laboratory setting is higher than observed in fleet diving. Use of the 40 fsw for 200 min schedule in a decompression computer is likely to result in DCS incidence 2.5- to 70-fold greater than that observed in U.S. Navy diving using table-based procedures.
Ball
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Naval Medical Research Institute, Bethesda, MD, USA.
Parker
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D000328:Adult; D000465:Algorithms; D001827:Body Height; D001835:Body Weight; D003665:Decompression Sickness / Q000209:etiology*; D004242:Diving / Q000009:adverse effects*; D006801:Humans; D015994:Incidence; D008297:Male; D008889:Military Personnel; D008954:Models, Biological; D009010:Monte Carlo Method; D009326:Naval Medicine; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012307:Risk Factors; D012623:Seawater; D013997:Time Factors; D014481:United States