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On Wed, 29 Jun 1994 JOHNCREA@de*.co* wrote: > Rich, > > Obviously, considering that oxygen should (based on lipid solubility) > be about 2x as narcotic as a comparable partial pressure of nitrogen. > > However, the research done (1 study) suggested that oxygen was about > equi-potent with nitrogen (maybe due to the metabolic pathway and > consumption of oxygen at the cellular level). > > John As has been discussed before, oxygen seems to have sort of a synergistic effect with nitrogen in causing narcosis (i.e., pure O2 at super-high partial pressures doesn't seem to have much of a narcotic effect). I suspect, therefore, that oxygen and nitrogen will not be equi-potent at all ratios and at all depths. My experience (admittedly anecdotal) tells me that at about 200', if you increase the oxygen:nitrogen ratio, narcosis is exacerbated. I hypothesize that under similar conditions, if I decrease that ratio (i.e., more nitrogen), narcosis may similarly decrease. This makes sense from a lipid-solubility standpoint if you view the amount of available oxygen in the tissues as being a certain amount ABOVE what is being metabolized: At relatively low inspired PPO2's, a larger proportion of total dissolved O2 is metabolized when compared with relatively high inspired PPO2's. A metaphor might be a combustion reaction: nitrogen being the analog of fuel, and oxygen serving the same analagous function as oxidizer: Oxygen alone is non-flammable (or, in our case, non-narcotic); combine it with a fuel and you can have a combustion (combine it with nitrogen and you can have narcosis). You can limit or increase the vigor of a burning flame by limiting or increasing the availability of oxygen. I'm suggesting that, perhaps, at the sort of depths we're talking about (150-250 feet), the abundance of oxygen in the breathing mix might govern the extent of narcosis severity (within certain parameters). Now bear in mind, I realize there is no similarirty between a combustion reaction and the physiology of narcosis at the molecular level: I'm just using it as a metaphor. I'll let you know what the results of my little informal study turn out to be (I'll probably try it early next year). Aloha, Rich
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