Nitrox workshop dings - Divers Alert Network

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Rubicon Foundation Archive (http://rubicon-foundation.org)Vann: Nitrox Diving Data ReviewFigure 6 shows the estimated maximum inspired oxygen partial pressure in 74 nitrox divinginjuries. About 5% of these exposures had a maximum oxygen partial pressure of 1.71-1.8 atm,but the most common partial pressures (45%) were 1.21-1.4 atm.Inspired Oxgen Partial Pressure (atm)Figure 6. Maximum oxygen partial pressure and nitrox diving injuries.Data were available for nine nitrox fatalities, but of these, only five had sufficientinformation for a minimal description of the dive profile. Table 11 summarizes information forthree of the cases. The maximum oxygen partial pressure did not exceed 1.35 atm in these cases,and there was no indication of oxygen toxicity. The critical events appeared to be rapid ascent orrunning out of gas.Table 11. Nitrox fatalities.DepthTime%PIO2(fsw)(min)Oxygen(atm)Comment4030320.71Rapid ascent9115361.35Rapid ascent11538301.35Out of AirTwo nitrox fatalities did have indications that oxygen convulsions may have occurred. Inone case, an experienced diver was found unconscious at 135 fsw after about 45 min of breathing38% oxygen in nitrogen with an inspired oxygen partial pressure of 1.93 atm. A seizure was notobserved. The diver was not formally trained in nitrox diving but knew that the oxygen partialpressure was higher than recommended. He believed he could handle the mix and accepted therisk.The second case involved an experienced cave diver who was observed to convulse during acave dive. His dive profile involved 15 min on air at 80-104 fsw (0.87 atm maximum P1O2)followed by 45 min on 40% oxygen in nitrogen at the maximum depth of 84 fsw (maximum 1.42atm P1O2).27
Rubicon Foundation Archive (http://rubicon-foundation.org)Lang (ed.): DAN Nitrox Workshop, Divers Alert Network, November 2000SummaryLaboratory and open-water experience suggests that nitrox diving may be practiced with lowrisks of decompression sickness and oxygen toxicity. DAN has data on mixed gas diving datingfrom 1990 for diving fatalities, from 1995 for diving injuries, and from 1997 for safe dives. Ahigher proportion of safe divers used nitrox than of divers who were injured or died. Nitroxdivers were older than air divers, and over 60% of nitrox divers who dived safely had specialtytraining. Safe nitrox diving was most common aboard charter boats, and there were no air ornitrox fatalities from liveaboards. Nitrox divers who dived safely dived less intensively (fewerdives over more days) than did air divers. In general, nitrox divers dived deeper than did airdivers regardless of whether they dived safely, were injured, or died. For either air or nitrox,injured divers and diving fatalities had higher proportions of rapid ascent and running out of gasthan did safe divers. The maximum oxygen partial pressures were above 1.3 atm for half of 74injured nitrox divers. While the incidence of oxygen toxicity during nitrox diving is unknown,convulsions and/or unconsciousness was reported for three divers who had maximum oxygenpartial pressures of 1.4, 1.6, and 1.9 atm. Careful depth control is important to avoid excessivelyhigh oxygen partial pressures during nitrox diving. In the future, DAN will increase its efforts tocollect data about mixed gas divers who dive safely, are injured, or die.ReferencesCharlton, W.H. 1998. Diving at Bozburun-1998. INA Quarterly 25(4): 14-15.Fife, C.E., R.D. Vann, G.Y. Mebane, and R.D. Dunford. 1990. Doppler surveillance of openwatermultiday repetitive diving. Undersea Biomed Res 17(Suppl): 220.Fife, C.E., G.W. Pollard, G.Y. Mebane, R.D. Vann, and A.E. Boso. 1991. A database of openwater,compressed air, multi-day repetitive dives to depths of 100-190 FSW. UnderseaBiomed Res 18(Suppl):71.Vann, R.D. 1982. Decompression theory and application. In: The physiology of diving andcompressed air work, 3rd edition. Bennett, P.B. and D.H. Elliott (eds). Bailliere Tindall,London. Pp. 352-382.Vann, R.D., P.J. Denoble, C.R. Sitzes, K.E. Harbaugh, W.A. Gerth, G.W. Pollard and W.H.Charlton. 1995. Project Dive Safety and scientific diving. In: Diving For Science. Harper,D.E. Jr, (ed.). American Academy of Underwater Sciences, Nahant, MA. Pp. 119-135.Vann, R.D., T.A. Fawcett, M.S. Currie, C.E. Fife, J. Zhang and C.A. Piantadosi. 1992a. No-stoprepetitive N2/O2 diving with surface interval O2 (SIO2): Phase I: Undersea Biomed Res19(Suppl):125.Vann, R.D., W.A. Gerth and W.H. Charlton. 1999. Operational testing of air and nitrox divetables. Undersea & Hyperbaric Med 26 (Suppl.): A127.28
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