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Hello Peter I am more interested in understanding what those guys (Rick, WKPP folks, etc) do regarding the CNS clock DURING the long deco stops. In other words, if we are going to stick this the current "CNS% clock wisdom", how can we make loooooong deco schedules (more than 2 hours?) possible? >but...seriously folks, what evidence is there that the CNS clock "resets" >rapidly at the surface as you indicate? I know the *theory* is that you >consume O2 and are offgassed rapidly - but what if the effect is >one of O2 on membrane stability? (Which seems more plausible). I don't >know how you would measure that effect on cumulative dives, except >empirically. Also the O2 clock assumes an equal increase of risk for each >minute passed at a given pPO2 - risk analysis curves rarely look like that >and the Navy model for CNS O2 toxicity (ref in the lists - it's Underwater >Scuba Magazine - April issue) has a curve not a line. So?? I did some research on the subject and found the following text searching on the "online" NOAA manual (Section 3.3 - Oxygen Poisoning), on the same Underwater Scuba Magazine WWW site: " At the present time, the most useful procedure for extending human oxygen tolerance employs systematic alternation of hyperoxic and normoxic exposure intervals to increase greatly the tolerable duration of exposure to a selected level of hyperoxia. This procedure takes practical advantage of the empirical observation that many early, subclinical effects of oxygen toxicity are reversed more rapidly than they develop. Interrupted exposure as a means of oxygen tolerance extension was innitially studied in animals (Clark 1983, Lambertsen 1978), and its effectiveness was later demonstrated directly in man (Hendricks et al. 1977). Although periodic interruption of oxygen exposure has been a component of the U.S. Navy oxygen treatment tables (US Navy 1985) for many years, its potential for oxygen tolerance extension has been only minimally exploited to date." I'm interested in more info on this subject, via cientific studies (how can we get a hold on the studies mentioned above?) or via practical experiences. Maybe Rick, Irvine and others that do long deco stops, and probably "blow" their CNS% clock on those, can jump in and share with us their experience on this theme. --- Mauricio Henriques Network Consultant Phone: +[55](21)297-1122 x.4715 Digital Equipment Co. FAX: +[55](21)220-3324 Brazil mauricio@va*.en*.de*.co* ---
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