Ah. That might be true... I don't think many of those reached long expositions to high pO2, I might be wrong though. You need to reach 90m to get to 2b pO2, so there's little "real exposure" at that depth imo.
Nitrox: Narcosis myth?
- Thread starter northernone
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
DevonDiver
N/A
Actually, this side discussion prompted me to do some reading. I wasn't aware that anesthesia can cause CNS toxicity... a CNS excitor. I assumed an anesthetic effect was a CNS suppressor.
Hi Steve. This has actually been done as part of an Israeli study. You can find it referenced in the DAN tech dive proceedings 2010, p. 77. You can download it here: Technical Diving Conference Proceedings.. It was indeed a double blind study, and the outcome was that there was no difference in registered narcosis level of participants on air and ean36.
This is interesting because it goes against some other studies, that clearly indicate nitrogen is more narcotic than oxygen. I.e. Albano et al. who found that divers breathing oxygen/nitrogen mixes with only 4% o2 vs divers breathing 21% oxygen, performed significantly better. Mind you, this was at 90m depth where very few would be foolish enough to dive either mix.
Perhaps it's fair to say only, that in the depths dived by mainstream recreational divers, the differences between narcotic potential of oxygen and nitrogen exist, but appear to be insignificant.
That too, although slightly modified, has been tested but the exact reference escapes me at the moment. Someone can maybe help? - basically it's been demonstrated, that the narcosis reported (and observed through experimentation) is very, very influenced by the notion of what that narcosis should be like. People told they will be nearly incapacitated by breathing whatever mix, indeed become so. People who have the opposite expectation, perform significantly better, no matter what identical mix they are breathing.
In a real life example, we see this all the time, but tend to attribute it something else perhaps (habituation , adaptation, being inherently more bad ass etc.) When instructors take first time deep diving students on 30m/40m deep dives, some students become visibly influenced. Yet the instructors never (?) seem to get affected, despite breathing the same air. Certainly curious I feel.
Last edited:
Do you have a direct link?
DevonDiver
N/A
The issue with oxygen is that Meyer-Overton doesn't account for the metabolism of a gas.
Sure, when saturated into olive oil, oxygen shows a higher narcotic potential than nitrogen.
However, unlike olive oil, the brain voraciously metabolises oxygen, reducing both FO2 and ppO2.
This effect, to a greater or lesser degree, might reduce the narcotic effect of oxygen; explaining why numerous studies have failed to provide conclusive evidence of the actual narcotic impact of varied FO2 breathing gasses.
Sure, when saturated into olive oil, oxygen shows a higher narcotic potential than nitrogen.
However, unlike olive oil, the brain voraciously metabolises oxygen, reducing both FO2 and ppO2.
This effect, to a greater or lesser degree, might reduce the narcotic effect of oxygen; explaining why numerous studies have failed to provide conclusive evidence of the actual narcotic impact of varied FO2 breathing gasses.
From the paper he linked, I understand it should be this one. http://www.heilweil.com/erez/nitrox/Nitrox_Experiment.pdf
That is a very interesting study. They studied both cognitive ability and also folks ability to assess their thinking and their confidence in their assessment. My summary after a quick read is
1. Depth had a definite affect on ability in the tests
2. Folks were not able to assess their lessened ability at depth
3. Folks who were not that confident in their assessment when shallow became more confident with depth.
1 was no surprise to me
2 I suspected but did not know if true
3 Was a surprise and very interesting
1. Depth had a definite affect on ability in the tests
2. Folks were not able to assess their lessened ability at depth
3. Folks who were not that confident in their assessment when shallow became more confident with depth.
1 was no surprise to me
2 I suspected but did not know if true
3 Was a surprise and very interesting
That's about the same as with alcohol and hypothermia: the first thing to go is your judgement of the situation.
People's expectations can have a big effect on their perceptions. Remember once in college one of the brothers bought a keg of lowenbrau to celebrate his engagement. He also bought a keg of millers. Put both in the tap system downstairs. When folks would come down for an imported beer we would offer them a miller. Only when they said this is not lowenbrau did we give them one. The majority would go on about what a great beer the millers was and how it was so much better than the beer we usually drank which was millers.
I'm guessing that the two kegs were nearly indistinguishable in terms of content.
Löwenbräu - Wikipedia
In 1975, Miller Brewing acquired the North American rights to Löwenbräu. After two years of exports, Miller began brewing Löwenbräu domestically with an Americanized recipe, and exports of Munich Löwenbräu to North America ceased. Anheuser-Busch, whose Michelob brand Miller had intended Löwenbräu to compete with, called the attention of regulators and the public to the changes Miller had made to mass-produce the beer for the American market, changes which introduced artificial ingredients that would not have been allowed under the German Reinheitsgebot that Miller had advertised Löwenbräu as being compliant with. No regulatory action was taken, but sales of Löwenbräu dropped to the point where it was clear the brand would not seriously compete with Michelob for the premium-beer segment.
Similar threads
