Oxygen Narcosis
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I am not sure I understand this. Are you saying that you consider EANx 32 to be less narcotic than air because it has a lower PN2?
Some agencies teach calculating the END using total oxygen and nitrogen tensions, and some just use nitrogen. I can't remember who does what at this point. I think it's more valid to consider both, which is what I do.
My personal belief is that cognitive function is impaired much earlier than people discuss. That isn't science; it's observation. It's observing how difficult people (even experienced divers) seem to find it to remember a sequence of activities which were pretty thoroughly discussed on land before diving. In a lot of my classes, even at 30 feet, people make mistakes and have difficulty remembering things they were told -- in new divers, that's understandable, since they're on cognitive overload anyway, but when you are doing critical skills dives for technical classes and the students can't remember what order they're supposed to do things in, it does make you wonder. Over ten years, I have seen enough of it to believe that there is something to being underwater that starts making us a little stupid almost right away -- the "Martini rule".
People don't notice this, for the most part, because very little diving involves complex structure or requires remembering a sequence of events. Most diving involved maintaining buoyancy (and trim, if you care) and staying with the group, neither of which is complex. The author of this piece does identify one of the more complicated things we do when we dive, which is manage buttons on cameras and computers. I'm convinced one of the reasons people say you should learn your camera's controls to the point of unconscious competence if you want to be good in the water, may well be because you need that much training to be able to REMEMBER the steps in the water!
My personal belief is that cognitive function is impaired much earlier than people discuss. That isn't science; it's observation. It's observing how difficult people (even experienced divers) seem to find it to remember a sequence of activities which were pretty thoroughly discussed on land before diving. In a lot of my classes, even at 30 feet, people make mistakes and have difficulty remembering things they were told -- in new divers, that's understandable, since they're on cognitive overload anyway, but when you are doing critical skills dives for technical classes and the students can't remember what order they're supposed to do things in, it does make you wonder. Over ten years, I have seen enough of it to believe that there is something to being underwater that starts making us a little stupid almost right away -- the "Martini rule".
People don't notice this, for the most part, because very little diving involves complex structure or requires remembering a sequence of events. Most diving involved maintaining buoyancy (and trim, if you care) and staying with the group, neither of which is complex. The author of this piece does identify one of the more complicated things we do when we dive, which is manage buttons on cameras and computers. I'm convinced one of the reasons people say you should learn your camera's controls to the point of unconscious competence if you want to be good in the water, may well be because you need that much training to be able to REMEMBER the steps in the water!
100days-a-year
Contributor
John,yes.Have never experienced any noticeable narcosis on 02 at exposures far beyond recommended levels.Nor have I heard any anecdotes attesting such.Therefore I don't consider it appreciably narcotic.PP of N2 however is easier to quantify.
Anybody got some linky to studies showing impairment on 02 alone?
32% not being significantly less N2 than air in any case given the variability of onset and degree of impairment even on the same day, same diver.
Anybody got some linky to studies showing impairment on 02 alone?
32% not being significantly less N2 than air in any case given the variability of onset and degree of impairment even on the same day, same diver.
As I explained earlier you cannot test narcosis on O2 alone because you would have a toxing event first. All agencies that I know of teach that nitrox is as narcotic as air because according to the theory on how it works, O2 is as narcotic (or more) than N2.
So what is your basis for saying nitrox is less narcotic, in defiance of currently accepted theory?
100days-a-year
Contributor
If 02 narcosis requires toxing to quantify any effect then how can it be considered as narcotic as N2?Pretty simple really.We have tons of chamber time to study,they max at 3.2 P02 correct?Ever hear of anyone getting goofy in a chamber ride?It is one thing for an agency to state a claim,another to defend it's refutation.
I base my view on a passing grasp of math and physics,having dove high and excessive P02 as well as anecdotal evidence fellow divers doing the same as well as historical use of 02 rebreathers in depths far deeper than a 1.6 regularly.FWIW I dive 1.0 or so normally as my exposure is long,multiday and strenuous.
As far as agencies views...nitrox was voodoo gas as was helium.As product liability issues and out of shape divers have lengthened ascent and decompression times I refrained as it never became an issue.Comparing my actual dive profiles to conventional wisdom,I am bent and dead as are the dozen or so fellows who do what I do.Remarkably good looking corpse I am.
Please understand I am not being a contrarian,I just see no valid evidence other than "because I (We) said so" and a hokey first year med school reference to a theoretical relationship between lipid solubility and narcosis.Other effects of diving(DON,HPNS,narcosis,oxtox,barotraumas,DCS etc) on the body are readily studied and even if not fully understood can be repeatably demonstrated and reams of studies validating the nature if not the precise mechanism and degree of effect.
I base my view on a passing grasp of math and physics,having dove high and excessive P02 as well as anecdotal evidence fellow divers doing the same as well as historical use of 02 rebreathers in depths far deeper than a 1.6 regularly.FWIW I dive 1.0 or so normally as my exposure is long,multiday and strenuous.
As far as agencies views...nitrox was voodoo gas as was helium.As product liability issues and out of shape divers have lengthened ascent and decompression times I refrained as it never became an issue.Comparing my actual dive profiles to conventional wisdom,I am bent and dead as are the dozen or so fellows who do what I do.Remarkably good looking corpse I am.
Please understand I am not being a contrarian,I just see no valid evidence other than "because I (We) said so" and a hokey first year med school reference to a theoretical relationship between lipid solubility and narcosis.Other effects of diving(DON,HPNS,narcosis,oxtox,barotraumas,DCS etc) on the body are readily studied and even if not fully understood can be repeatably demonstrated and reams of studies validating the nature if not the precise mechanism and degree of effect.
I got certified in 2008, and PADI stated clearly that O2 is as narcotic as N2. They also said that the purpose of nitrox is to reduce the absorption of nitrogen, thereby increasing NDL time and reducing the risk of DCI on any given dive profile, not to reduce the risk of narcosis. They also said that narcosis increases with depth and affects different people to differing degrees; it does not suddenly appear at a particular depth. Every so many feet (I forget how many) is like drinking one martini.
So pretty much every accusation the OP makes concerning the assertions of the training agencies is untrue. They do not ignore the effects of O2 and they do not claim that there is no narcotic effect at depths less than 100 feet.
OTOH, if the OP has encountered a dive trainer saying those things, he is right to disabuse that person of those notions.
I do not recall if the term "gas narcosis" had replaced the term "nitrogen narcosis" yet at the time I was certified.
So pretty much every accusation the OP makes concerning the assertions of the training agencies is untrue. They do not ignore the effects of O2 and they do not claim that there is no narcotic effect at depths less than 100 feet.
OTOH, if the OP has encountered a dive trainer saying those things, he is right to disabuse that person of those notions.
I do not recall if the term "gas narcosis" had replaced the term "nitrogen narcosis" yet at the time I was certified.
Some agencies are so lax they don't specify if O2 is to be considered narcotic or not. I recently had a TDI instructor who taught this way and I'm sure he's not the only one. From a practical perspective its mostly about the END formula. In the water it is what it is.
In the interest of technical correction, helium does have some (slight) narcotic potency too. And does some really weird things at extreme depths far beyond recreational limits.
Hello All,
Does anyone have a pdf copy of the following papers on "oxygen narcosis" that they'd be willing to send me or post a link to?
I would greatly appreciate it:
Francois
Bennett, P.B. “The narcotic effects of hyperbaric oxygen.” In: Wada J, and T. Iwa (eds.). Proceedings Fourth International Congress on Hyperbaric Medicine. Williams and Wilkins. Baltimore. (1970).
Linnarsson, D. et al. “Does oxygen contribute to the narcotic action of hyperbaric air?” In: Sterk, W. and L. Geeraedts (eds.). Proceedings XVIth Meeting of the European Undersea Biomedical Society. Foundation for Hyperbaric Medicine. Amsterdam. (1990).
And also:
Logan, J. A. "An evaluation of the equivalent air depth theory." United States Navy Experimental Diving Unit Technical Report. NEDU-RR-01-61, (1961).
Does anyone have a pdf copy of the following papers on "oxygen narcosis" that they'd be willing to send me or post a link to?
I would greatly appreciate it:
Francois
Bennett, P.B. “The narcotic effects of hyperbaric oxygen.” In: Wada J, and T. Iwa (eds.). Proceedings Fourth International Congress on Hyperbaric Medicine. Williams and Wilkins. Baltimore. (1970).
Linnarsson, D. et al. “Does oxygen contribute to the narcotic action of hyperbaric air?” In: Sterk, W. and L. Geeraedts (eds.). Proceedings XVIth Meeting of the European Undersea Biomedical Society. Foundation for Hyperbaric Medicine. Amsterdam. (1990).
And also:
Logan, J. A. "An evaluation of the equivalent air depth theory." United States Navy Experimental Diving Unit Technical Report. NEDU-RR-01-61, (1961).
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