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I wonder what the physical mechanism is. I once heard an explanation that goes something like this. The membranes surrounding the neurons have a high fat content, so that when they are exposed to a high partial pressure of lipid soluble inert gas (such as Nitrogen) they swell up. This produces the narcotic effect. With Helium, the opposite happens and the membrane shrinks. This is the cause of HPNS. It takes a much greater pressure, though. With trimix, the effects tend to cancel. I tried to check this out in Bennett and Elliot, but I was overcome by the MEGO effect (My Eyes Glaze Over). One thing I did notice is that lipid solubility is highly correlated with narcotic potency. This seems strange since the water/lipid solubility ratio apparently doesn't matter. I didn't see any data for Oxygen solubility. Mike McDiarmid wrote: > > There are others on this list with far more knowledge than I, but I > have been told that in determining the narcotic effect of a gas you > must consider its lipid solubility. Oxygen has a high lipid > solubility so therefore is in fact narcotic and should be considered > when determining the END of a mixture. He does not, or is very low, > so not a factor in the calculations. Bill Mee, George or JJ can > answer this one better. My apologies if I have mis-stated anything. > Traditional teachings by the agencies do not account for the O2 > content of a mixture in determining the END. This is a mistake. End > of subject. > > Mike > > ---Jsuw@ao*.co* wrote: > > > > When determining the acceptable narcosis exposure for a dive, it > seems that > > only the narcotic effect of nitrogen is considered. Oxygen is at > least as > > narcotic as nitrogen. Although helium is far less narcotic than > either, it > > still is an inert gas with potential to have narcotic properties. > > > > With this in mind, why is it that only nitrogen's narcotic effects are > > considered? How can the narcotic effect of the other gases be > accounted for? > > Does it matter? > > > > _________________________________________________________ > DO YOU YAHOO!? > Get your free @yahoo.com address at http://mail.yahoo.com
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