Oxygen narcotic?

[VE7DAC]

Don't think of it in terms of just PO2, think of it in terms of P(Narcotic Gasses), or PO2+N2. From a narcosis standpoint, it doesn't matter what the proportions of O2 and N2 are. They're equally narcotic. Breathing O2 at 80', in theory, should have the same narcotic potential as air (it obviously has other, separate issues).

If I want to keep my END at 100 or less, the maximum PO2+N2 I can have is 4.0. If I'm shallower than 100, problem solved. Just watch the PO2. If I'm deeper, just subtract that 4.0 from ambient pressure and convert the remaining balance to FHe.

That's a handy rule of thumb. And it makes sense that oxygen can contribute to narcosis, my initial confusion was about how much it contributes. Since it's not considerably narcotic on its own at 1.6 PPO2, I didn't consider that it would compound the narcosis from the nitrogen.

 

[helodriver87]

That's a handy rule of thumb. And it makes sense that oxygen can contribute to narcosis, my initial confusion was about how much it contributes. Since it's not considerably narcotic on its own at 1.6 PPO2, I didn't consider that it would compound the narcosis from the nitrogen.

It keeps the math really simple. Wanna go to 7ATA? Cool, your mix is 1.2 O2, 2.8 N2, 3.0 He. Convert to percentages and mix away. Standard gasses are even simpler and derived in the same way, just applied over a broader range of depths. I think you get the idea, but just a minor point, O2 doesn't compound nitrogen narcosis so much as it's additive. Thinking of them as narcotic gasses instead of individual elements helps.

 

[Jared0425]

Is there any specific information regarding the COMEX or U.S. Navy dives to beyond 2000 ft? A commercial diver told me that depths below 1200 are regular in the gulf but I don't know if that's just macho or real.

 

[rjack321]

Is there any specific information regarding the COMEX or U.S. Navy dives to beyond 2000 ft? A commercial diver told me that depths below 1200 are regular in the gulf but I don't know if that's just macho or real.

Those are saturation dives from a bell with recycled gas. So nothing like open circuit scuba.
@Akimbo can probably talk about that more.

 

[Subcooled]

We were taught that oxygen is considered pretty narcotic in our Fundies class very recently, and I will continue to treat it as narcotic.

Perhaps you should consult credible sources (academic research) instead of a diving agency.
You err on the safe side though, and that's a clever choice.

 

[Storker]

Perhaps you should consult credible sources (academic research) instead of a diving agency.

I'd love to see some credible sources. Cite?

 

[helodriver87]

I'd love to see some credible sources. Cite?

Considering the general scientific consensus on the matter is more or less "it should be somewhat comparable to nitrogen, but we don't know", I'm interested to see what he's got that contradicts what most people are teaching.

 

[uncfnp]

I'd love to see some credible sources. Cite?

Considering the general scientific consensus on the matter is more or less "it should be somewhat comparable to nitrogen, but we don't know", I'm interested to see what he's got that contradicts what most people are teaching.

One more time.

Objective vs. Subjective Evaluation of Cognitive Performance During 0.4-MPa Dives Breathing Air or Nitrox. - PubMed - NCBI


DISCUSSION:
“The results suggest that EANx could protect against decreased neuro-cognitive performance induced by inert gas narcosis.”

And Dr Simon Mitchell’s post #68 from this thread
Nitrox: Narcosis myth?

“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.”

 

[helodriver87]

One more time.

Objective vs. Subjective Evaluation of Cognitive Performance During 0.4-MPa Dives Breathing Air or Nitrox. - PubMed - NCBI


DISCUSSION:
“The results suggest that EANx could protect against decreased neuro-cognitive performance induced by inert gas narcosis.”

And Dr Simon Mitchell’s post #68 from this thread
Nitrox: Narcosis myth?

“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.”

One study is hardly conclusive. There are others that contradict those findings. And Mitchell's own quote states that the functional difference is quite small. Which is what we're talking about here. Talking about lipid solubility and such is interesting and helps to frame the issue, but functional application is what matters. And from a functional standpoint, O2 is basically comparable to nitrogen. It's not precise science to treat them the same, but it's smart dive planning.

 

[uncfnp]

One study is hardly conclusive. There are others that contradict those findings. And Mitchell's own quote states that the functional difference is quite small. Which is what we're talking about here. Talking about lipid solubility and such is interesting and helps to frame the issue, but functional application is what matters. And from a functional standpoint, O2 is basically comparable to nitrogen. It's not precise science to treat them the same, but it's smart dive planning.

A better counter argument would be to show me at least one objective study done under dive conditions that supports the claim that oxygen is just as (or more so) narcotic for divers.

The difference is between theory and lab verses real life studies that account for the human physiology.