Oxygen narcotic?

[Tassi Devil Diver]

"On balance, I favour the argument that oxygen is less narcotic at the pressures we can safely breathe because there is a substantial gap between inspired and tissue PO2 due to metabolism in the tissues that matter for a narcotic effect. In contrast, the gap between inspired and tissue tensions of nitrogen in the brain is almost zero because the brain is a very fast tissue. Having said that the functional difference in narcotic effect is probably quite small. If we really want to avoid narcosis, then breathing helium is the key.”

Simon M's quota above from earlier in this thread and from other threads on the topic is enough to tell me I don't need to worry about the narcotic effect of oxygen in my gas planning.

 

[helodriver87]

"On balance, I favour the argument that oxygen is less narcotic at the pressures we can safely breathe because there is a substantial gap between inspired and tissue PO2 due to metabolism in the tissues that matter for a narcotic effect. In contrast, the gap between inspired and tissue tensions of nitrogen in the brain is almost zero because the brain is a very fast tissue. Having said that the functional difference in narcotic effect is probably quite small. If we really want to avoid narcosis, then breathing helium is the key.”

Simon M's quota above from earlier in this thread and from other threads on the topic is enough to tell me I don't need to worry about the narcotic effect of oxygen in my gas planning.

Are you skipping the last two sentences? That quote, to me at least, is drawing a distinction between theory and application. "The functional difference is probably quite small." Meaning even though O2 is probably slightly less narcotic, you're probably not going to notice a difference in practice. So you're better off treating O2 and nitrogen the same and just using helium.

 

[Tassi Devil Diver]

^ and that is exactly what I do use He in my CCR dil for any dive deeper than 30m adhering to latest advice on gas density and select O2 narcotic as NO in MultieDeco configuration.

 

[uncfnp]

Well its an abstract, published almost 30 years ago. At least a couple of the authors are deceased now. So good luck finding details.

You are right. The abstracts are all that I can access for each study. Given the low number of participants for both, I wonder if either study has enough statistical power for a meaningful conclusion.

Not surprisingly it seems the opinion of Dr Mitchell is the best and last word.

 

[Storker]

Simon M's quota above from earlier in this thread and from other threads on the topic is enough to tell me I don't need to worry about the narcotic effect of oxygen in my gas planning.

"less narcotic" ≠ "not narcotic".
And "I favour the argument" is hardly a scientifically proven conclusion.

Add to that that the bottom line is to use He if you want to avoid narcosis, and I have a very hard time understanding how this can be interpreted as reckoning that END=EAD. Which I have the impression is your position.

 

[EFX]

I'm jumping in late. I always thought END = EAD. Just different names for the same thing. If not, what is the difference?

 

[NAM001]

I was having fun because what I quoted said "Both studies probably have very valid findings and are reflective of the fact that we really don't know to what extent O2 is narcotic. It should be more narcotic than oxygen, but metabolization likely reduces that effect."

I always thought O2 was oxygen.. maybe I'm just as I typed, confused.

Until i did a tech class I thought the same N2 is the problem and O2 is O2. And I was right as far as the rec depths go.

 

[helodriver87]

I'm jumping in late. I always thought END = EAD. Just different names for the same thing. If not, what is the difference?

It depends on whether you consider O2 narcotic. If you do, END is purely a measure of how narced you'll feel at a given depth based on the mixture you're using. For example, 18/45 at 200' has an END of 95'. Meaning that the partial pressure of narcotic gasses (O2 and N2) in the mix at that depth are a hair under 4.0. You'd feel the same level of narcosis at 95' on air or nitrox. EAD would be 76' since O2 isn't considered narcotic. I use EAD to make air tables work with nitrox, but that's about it. END for actual gas mixture selection.

 

[cerich]

Until i did a tech class I thought the same N2 is the problem and O2 is O2. And I was right as far as the rec depths go.

the ONLY gas mentioned in my post was oxygen. Where did you get N2?

 

[Storker]

I'm jumping in late. I always thought END = EAD. Just different names for the same thing. If not, what is the difference?

EAD: Equivalent air depth. EAD is a tool for using air tables to find your PG and your NDL when diving nitrox. EAD=depth·FN2/0.79
END: Equivalent narcotic depth. If I were trimix certified I'd use END to decide how much He I'd put in my mix for a given planned dive. END=depth·(1-F(non-narcotic gases))

If O2 weren't narcotic, EAD and END would be the same for any mix, except for that 1/0.79 factor. I am one of those who prefer to assume that O2 is about as narcotic as N2.