Is there any evidence that suggests surface beathing 100% O2 before a deep dive on air reduces the likelihood of being narked?
Doubt it as you would be straight onto 78% N2 as soon as you descend with ever increasing partial pressures the deeper you go. Every breath would flush the lungs of O2, which can only be good as below 6m and ppo2 of 1.6 the cns toxicity risk increases. Therefore Is wager the answer to be marginal if at all. More to the point, why bother? If you KNOW you're going to be narced at x depth, then dive shallower or replace some of that nasty Nitrogen with Helium. This is exactly what I have done for a 48m dive on Saturday.
That's not strictly true - you could be at greater risk with Nitrox. It also doesn't really address the original question about narcosis
I've certainly never read anything that suggests pre-breathing a narcotic gas like Oxygen before a dive will reduce narcosis on the dive. Why would it?
That was what I thought, but I haven't ever heard of a piece of conclusive evidence that implies that oxygen is narcotic, which is why I believe some agencies, such as IANTD, teach that oxygen is not narcotic. Unless such evidence does exist (and I mean reliable, empirical evidence, not just a speculative theory), then claiming that oxygen is narcotic is no more meaningful than claiming there is a little green man that lives in a cave on Mars.
What have you got to lose by assuming it is narcotic? Compared to believing little green man lives in cave on Mars? Oh, and which is more or less likely in the scenario of say, oh ummmmmm, I dunno....ummmmmm, scuba diving?
You have nothing to lose in terms of practical application, but when we talk about oxygen, it is wrong to describe it as a narcotic gas when it is quite conceivable that it isn't. I didn't mean that there actually is a little green man on Mars, and of course it's not relevant to diving. All I was trying to demonstrate was that it would be unjustified to make such a claim without any valid evidence supporting it. Hence my challenge of Garf's assertion that oxygen is narcotic.
O2 is narcotic, on a recent dive I used 32% down to 36m then swopped onto 21/10 which was an air top on a previous dives gas. Although I had no signs of narcosis I did notice when I started breating the weak helium mix that there was a slight clouding that cleared after 3 breaths and colour became brighter. This excercise is something in going to repeat with air and the same mix at the same depth as im convinced it was the increased level of O2 that I was breathing that caused the cloudyness as both gasses had similar nitrogen content. Intrested to see if nitrogen nark and O2 nark have different effects.
Again, I think you mean, in your opinion based on one sujective experience, oxygen appeared to be narcotic Well, it's what you would have meant if you were a normal, rational internet persona, but this is you we are talking about...
I think if you look up the definition of the word 'narcotics' you might find it means a substance that, dulls the sences, can cause convulsions above other things, so yes O2 is narcotic as we know it definatly can cause convulsions and has done.
Nope, I meant a Narcotic Gas. Oxygen. As there is no definitive proof that Oxygen is or is not narcotic, then the logical and indeed only safe option is to assume it is narcotic. you have nothing to lose by assuming it is narcotic, and everything to lose by assuming it isn't. G
Something else on the DISRC worth reading http://www.disrc.com/index.php?opti...ure&catid=40:medical-and-hyberbaric&Itemid=75 A little technical but provides some understanding of O2 narcosis. In answer to the OP, never heard of that, and TBH, I doubt it would work. How quickly would the O2 be metabolised and replaced by N2 in the tissues? Pretty fast I would guess, therefore any benefits (even if O2 wasn't narcotic) would be so short lived so as not to be useful. Regards
