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[H2Andy]

if you go by the Bunsen Solubility Coefficient (i.e. narcotic potential)
nitrogen has a 0.052 coefficient, and O2 has a 0.110 (meaning it is twice as narcotic, potentially).

however, since O2 is metabolized, this coefficient is probably not accurate

let me run some numbers (sorry guys)

let's say you start to notice the narcotic effects of nitrogen at 100 feet (on average here, guys). if you are diving air, that is a nitrogen partial pressure of 3.18

so... if O2 had the same narcotic effect, and it would be noticeable at 3.18 partial pressure, that means you would begin to feel the narcotic effects of O2 (diving air, as above) at 499 feet

assuming that O2 is TWICE as narcotic as nitrogen, then you would start to feel the narcotic effects at around 250 feet on .21 O2 (putting aside the toxicity issue)

however, using Trimix, you can dive to 250 feet, easily, and eliminate the narcotic effects of air, while still having O2 in your mix (of course).

thus, i think that because O2 is metabolized, its narcotic (not toxic) ability is greatly overestimated.

 

[lamont]

Can anybody verify this with references? I have been looking, and everything I have found, other than a study by Dr. Bill Hamilton, refutes the quote. Based upon my reading, I suspect the claim that oxygen is as narcotic as nitrogen is most likely false.

What is the actual point of this argument? With either EAN21 or EAN32 at 100 fsw you've got basically the same amount of N2 in your gas and I know I've turned dives at 90 fsw on EAN32 because I got a severe narc hit on that particular day. Diving 30/30 or 21/35 is totally different and you can argue about if its the reduction of N2 or the addition of He, but its all kind of moot -- you can't dive EAN60 to 100 fsw (same nitrogen as 30/30 only no helium) because you'll tox and die. I'll take the helium mix over the nitrox...

 

[PerroneFord]

Given this, would diving nitrox actually cause you to feel MORE narcotic since we are increasing the amount of the more highly narcotic gas? Or would we feel less narcosis because the oxygen doesn't feel narcotic until we're deeper?

If the latter, then all the more reason to dive Nitrox, yes?

 

[H2Andy]

one thing i noticed while figuring out the above, is that O2's narcotic effects, if one assumes it is twice as narcotic as nitrogen, would begin to be felt at just below 1.6 PPO2.

in other words, just on the threshold of its toxicity issues

thus, if something goes wrong, it's going to be hard to decide whether it was a toxicity or an oxygen narcosis issue, even for the person undergoing the experience.

perhaps it's a combination of both?

 

[Doubles]

What is the actual point of this argument? With either EAN21 or EAN32 at 100 fsw you've got basically the same amount of N2 in your gas and I know I've turned dives at 90 fsw on EAN32 because I got a severe narc hit on that particular day. Diving 30/30 or 21/35 is totally different and you can argue about if its the reduction of N2 or the addition of He, but its all kind of moot -- you can't dive EAN60 to 100 fsw (same nitrogen as 30/30 only no helium) because you'll tox and die. I'll take the helium mix over the nitrox...

I think the point was about some previous posts. Myself and some others questioned whether this diver was narced at 75 fsw diving EAN36. The nitrogen loading would seem lite enough to not be able to cause significant narcosis. Others had commented that O2 was narcotic and could have been a contributing factor to the narcosis hypothisis.

Andy's math is interesting

I have seen divers fairly well narc'ed at 90fsw, but they were on air. I have a diver in mind who I think would be a good test case for testing the 02 narcotic effect. It would be interesting to confirm that they got narced on air and then try diving to that depth again on EAN36 which would be well under the 1.6 that Andy mentioned. Of course a test with 1 diver wouldn't mean much.

Cheers

 

[lamont]

I think the point was about some previous posts. Myself and some others questioned whether this diver was narced at 75 fsw diving EAN36. The nitrogen loading would seem lite enough to not be able to cause significant narcosis. Others had commented that O2 was narcotic and could have been a contributing factor to the narcosis hypothisis.

Andy's math is interesting

I have seen divers fairly well narc'ed at 90fsw, but they were on air. I have a diver in mind who I think would be a good test case for testing the 02 narcotic effect. It would be interesting to confirm that they got narced on air and then try diving to that depth again on EAN36 which would be well under the 1.6 that Andy mentioned. Of course a test with 1 diver wouldn't mean much.

Cheers

Right, and my point is that the difference between EAN21 and EAN36 is insignificant compared to day-to-day variability in susceptability to narcosis no matter how narcotic O2 is or is not. Even assuming that O2 has zero narcosis you're talking about the difference between 73 feet of narcosis on EAN36 vs. 100 feet of narcosis on 21 at 100 fsw. Since I've had dives on 21% at 100 fsw where I couldn't notice the narcosis and I've had dives to 100 fsw on 32% where the world went all wiggly and I called the dive, I doubt the O2 is relevant at all. Even assuming the O2 is totally non-narcotic it is just going to shift the bell curve so that you are slightly less likely to have the "world all wiggly" kind of dives at 100 fsw, but it isn't going to significantly prevent them. Diving on 30/30, though, will prevent a lot of those kinds of narcs and can largely completely prevent narcosis at those depths unless you build up CO2...

And its not just that a test with a single diver isn't going to be worth much. You're going to have to build up a series of hundreds of dives to be able to distinguish between the two bellcurves and you'll be swamped with measurement error and placebo effects. You won't be able to get any conclusive results.

The answer to the question "is O2 narcotic?" is "helium".

 

[gcbryan]

I've done no research on this so I'm just curious...didn't I read earlier in this thread that helium is 25% less narcotic than nitrogen? If so, for someone who gets narced around 100 fsw even with helium aren't they going to be narced anyway if they go to 200 fsw for example?

My point or question is for those who suggest that a helium mix is needed below 100 fsw because they can feel the narcosis at that level but who are interesting in technical diving and plan to go below 200 fsw on an appropriate helium mix why wouldn't that person be narced at that depth (if helium is only 25% less narcotic than nitrogen). Perhaps I am wrong about helium only being 25% less narcotic. Before I read that post I thought helium was much less narcotic rather than on 25% less than nitrogen.

 

[lamont]

I've done no research on this so I'm just curious...didn't I read earlier in this thread that helium is 25% less narcotic than nitrogen? If so, for someone who gets narced around 100 fsw even with helium aren't they going to be narced anyway if they go to 200 fsw for example?

My point or question is for those who suggest that a helium mix is needed below 100 fsw because they can feel the narcosis at that level but who are interesting in technical diving and plan to go below 200 fsw on an appropriate helium mix why wouldn't that person be narced at that depth (if helium is only 25% less narcotic than nitrogen). Perhaps I am wrong about helium only being 25% less narcotic. Before I read that post I thought helium was much less narcotic rather than on 25% less than nitrogen.

I think it is less narcotic and that the oil/water solubility ratio doesn't actually track narcosis for helium...

 

[TheRedHead]

With helium mixes, you choose an Equivalent Narcotic Depth of air that you feel comfortable with. I've been narced at 110 feet on EAN32. I don't think Nitrox signifcantly reduces narcosis.

 

[H2Andy]

I don't think Nitrox signifcantly reduces narcosis.

i think there's plenty of evidence you're right