Nitrox and Reducing Nitrogen Narcosis

[Dan Weidert]

I was in the hospital, after the operation, I breathed 100% oxygen during 12 hours, I had narcosis. I don't believe nitrox reduced narcosis.

100% oxygen at the surface is approximately 1 atmosphere absolute (depending on elevation and atmospheric pressure). If you look up O2 exposure times on the PADI DSAT table, in the 1.0 ata column you find 300 minutes (5 hours) to be 100% of allowable oxygen exposure.

While the gas coming out of the wall or tank is 100% oxygen, the gas you actually end up inhaling from the mask or nasal canula is not, thank goodness.

Dan

 

[Blackwood]

Dan,

The concerns in the chamber are pulmonary-related, not CNS related. CNS hits kill because the victim usually drowns. It's hard to drown in a dry chamber.

Also, anecdotal evidence suggests that we are far less susceptible to CNS tox when we're dry. I don't know why.

If you really screw up, you might find yourself breathing oxygen under pressure for a lot longer than you think.

 

[ppo2_diver]

I wasn't aware of O2's narcotic effects (only its toxicity). I'm curous, do you know at what depths and percentages of oxygen in the mix do you feel noticeable narcotic effects from oxygen? And are the effect similar to nitrogen narcosis?

It's going to vary by individual. I've never noticed being narced at 110 feet. But that doesn't mean I wasn't narced. Narcosis will affect each individual differently and narcosis also will come on strange at different depths for the same individual.

 

[String]

Thanks, that's quite helpful. I found this table online (http://www.bimson.com/diving/end.pdf) and sort of see what you mean. According to the table (I'm assuming it was correctly calculated), a dive on EAN32 to 34 meters has an END of 28 meters. Does that 6-meter difference not result in much of a difference in risk of nitrogen narcosis? I have little experience in this area, but I would think that diving at 90 feet (on air) poses a non-trivially lower risk of getting narced than diving at 110 feet.

That is assuming oxygen isn't narcotic. Most theory now suggests otherwise - its as or even more narcotic than Nitrogen and the effects are cumulative.

 

[wedivebc]

It is my belief that oxygen is less narcotic than nitrogen. It is also my belief that by the time you get deep enough to experience noticable impairment from narcosis the amount of oxygen is reduced due to CNS concerns that it makes little difference.

 

[Blackwood]

That is assuming oxygen isn't narcotic. Most theory now suggests otherwise - its as or even more narcotic than Nitrogen and the effects are cumulative.

It's more than theory. It's been observed in chambers.

 

[String]

It's more than theory. It's been observed in chambers.

Got any links for the papers? Would be nice to have those in my armoury for when these topics keep popping up

Ive got links to the Meyer-Overton theory and lipid solubility but couldn't find any actual data from real tests.

 

[Rhone Man]

According to the table published in Wikipedia (Nitrogen narcosis - Wikipedia, the free encyclopedia), Oxygen in 1.7 times more narcotic than nitrogen. So if your mix has (say) 36% Oxygen, then it would be in aggregate 10.5% more narcotic than air.

My highly unscientific view is that Europeans seem to be keener on the "oxygen is less narcotic" approach, whereas North Americans see it as more narcotic. I base that highly unscientific view on different software packages which I play around with and the END calculations on the European ones all seem to differ in that way.

 

[Blackwood]

Got any links for the papers? Would be nice to have those in my armoury for when these topics keep popping up

Ive got links to the Meyer-Overton theory and lipid solubility but couldn't find any actual data from real tests.

Yah, that Meyer Overton test has never held much sway over me.

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