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On Sat, 26 Apr 1997 09:43:36 -0400 (EDT) <CHKBOONE@ao*.co*> writes: > So you are suggesting that the END calculations used by trimix >divers is meaningless ? I hadn't thought about that. I suppose EAD would be more correct. Trimix is a whole different issue. Now we have introduced helium into the picture, which, as we all know, has only a tiny fraction of the narcotic potential of nitrogen (or oxygen). Therefore, replacing some of the nitrogen (and oxygen) will reduce the overall narcotic effect of the gas mix. Measurement of actual narcosis is difficult. Also the physiological effects of different gasses in a breathing mix and their relationship to partial pressures and one another are not fully understood. Thus, END (or EAD) is only a simplified rule-of-thumb anyway and is probably adequate for prediction of the approximate narcotic effect of any given gas. Narcosis is dependent upon so many other poorly defined factors for any given diver on any specific dive that this should come as no surprise. > If Nitrogen Narcosis is caused by or a direct result of an >increased partial preasure of Nitrogen how could reducing >that partial pressure not effect the degree of narcosis ? Easy one!... Many believe, narcosis (note, I have not said "nitrogen narcosis" or even "inert gas narcosis") is not due solely to the effects of increased nitrogen partial pressure. If, as I originally stated, oxygen has a similar (or greater) narcotic potential to nitrogen, then EANX will have an equal (or greater) narcotic effect to air. > I have been meaning to do some more looking into this claim >of a narcotic effect associated with Oxygen because several >divers I respect insist it is so. I suspect that it will be somewhat >different from the effects of N2 and will probably have to do with >the oxidation of some vital protine or enzyme. I can't help you here as I am not an expert in hyperbaric physiology. Indeed, many of those that are experts seem to be uncertain about this one. However, from the reading I have managed to do and the opinions of those whose judgement and expertise I value, I see no reason why nitrogen should have sole claim to be the only component of air capable of inducing narcosis at elevated partial pressures. Most people are using nitrox primarily to reduce their decompression obligation or add a safety factor. Reduced narcosis (real or imagined -- and difficult to quantify) is a secondary consideration. For the time being (and unless you can provide scientific evidence to convince me otherwise), I prefer to believe that oxygen has a narcotic potential equal to or greater than that of nitrogen. Therefore, I hold to my original OPINION that breathing nitrox confers no narcosis reduction. I CERTAINLY would NEVER rely upon any calculated END as an indicator of reduced mental impairment when planning nitrox dives in the 100 to 130 ft depth range. For trimix dives, END is probably as good as any other means of approximating the expected impairment due to narcosis. Flame away....... Philip -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send list subscription requests to `techdiver-request@aquanaut.com'.
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