Oxygen and narcosis

[BigJetDriver]

I know this feeling... it's not like I get spanked or anything but I can definatly precieve (sic) a bit of fuzzyness. I get roller coaster knees sometimes at the gas switch.

Of course, gentlemen, this has NOTHING to do with the fact that you are going from 30% oxygen, 30% helium, which leaves 39% NITROGEN, and 1% exotic gases, to EANX 50/50 which has 49%NITROGEN, and 1% etc. does it?

Sorry, just giving a bit of a razz. No offense meant. Just a suggestion that this might be the explanation, rather than the oxygen hypothesis.

 

[Saturation]

Of course, gentlemen, this has NOTHING to do with the fact that you are going from 30% oxygen, 30% helium, which leaves 39% NITROGEN, and 1% exotic gases, to EANX 50/50 which has 49%NITROGEN, and 1% etc. does it?

Of course not, since you have made up your mind already.

I concur with BigJetDriver69's position and analysis on this thread.

 

[dteubner]

According to PADI, the prevailing theory about narcosis is that oxygen is equal to or more than narcotic than nitrogen. To quote PADI/DSAT (Diving Science and Technology), “nitrogen and oxygen are both narcotic, and your equivalent narcotic depth (END) does not change as you challenge the ratio of oxygen and nitrogen”.

This is based on the “Meyer-Overton hypothesis” that says: gas absorption into the nerve cell lipids interferes with nerve impulse transmissions, which results in narcosis.

Gas solubility varies with different gasses depending on the solubility; the higher the solubility the higher the potential for narcosis. Since Oxygen is twice as soluble as nitrogen; it suggests that it is potentially more narcotic than nitrogen. The theory also suggests however, that this is offset somewhat by your body metabolizing oxygen. Not enough to make it less narcotic however.


-Steve

Nitrogen is an inert gas. The partial pressure of nitrogen in tissues (including neuronal membranes) rises over time to become the same as the partial pressure of nitrogen in the arterial blood which is equal (at a first approximation) to the partial pressure of nitrogen in the inspired gas.

This is fundamentally NOT TRUE of oxygen. In my rebreatherworld post (quoted by wedivebc and Bigjetdiver69) I expalin that the partial pressure of oxygen in the tissues is tiny compared to the nitrogen. Even if you accept that oxygen is twice as narcotic as nitrogen (which it probably is based on lipid solubility) the effect is still not significant (Twice bvgger all is still bvgger all)

The Meyer-Overton hypothesis predicts that narcosis will occur depending on the lipid solubility of a gas and its partial pressure. If the partial pressure in the tissues is low (and for oxygen it is) then the narcosis effect will me small unless the lipid solubility is enormous (which for oxygen it isn't).

Just to make a few other small obsevations. Narcosis is related to lipid solubility, not size. Hydrogen is both smaller and more narcotic than helium.

Nitrox 50 has more nitrogen in it than trimix 30/30

Dave T

 

[Dr Deco]

Hello readers:

This topic has been discussed over the years on this FORUM. One the basis of the Overton-Meyer relationship, oxygen is more soluble [on a molar basis] than nitrogen and thus would be more narcotic. The relationship does not discuss a mechanism, only a correlation. It is for inert gases [and vapors, e.g., ether].

In the past, the leading theory of inert gas narcosis was called the “Critical Volume Hypothesis.” It stated that neural membranes were expanded by the dissolving inert gases; this disrupted the flow of sodium and potassium ions and interfered, therefore, with nerve impulse generation. Deficiencies have led to the abandonment of this concept.

The fact that oxygen is metabolized will reduce its concentration at the cellular level. Oxygen is not an inert gas and many factors will come into play. The generation of “reactive oxygen intermediates” [e.g., free radicals] is a big factor.

Many if not most divers feel that nitrox is less narcotic than air. The jury is still out.:06:

Dr Deco :doctor:

 

[Solitude Diver]

Hello readers: This topic has been discussed over the years on this FORUM. Dr Deco :doctor:

As research progresses, and newcomers (like myself) join the forum to learn more, it will likely keep coming up, (and hopefully get more clarity as it goes).


Original poster:

In a recent discussion on nitrox I had with a few other divers, they took the position that oxygen was just as narcotic as nitrogen, and therefore using nitrox did not reduce narcosis compared to breathing air. It appears that they may have based this position on a statement made some time ago by Dr. Bill Hamilton of Hamilton Research that he had a little data which says a person's impairment is the same at high and low O2 levels of nitrox and so O2 is just as narcotic as nitrogen.

Dr. David Sawatzky wrote an article in Diver Magazine, December 1996, entitled "Oxygen Narcosis: Fact or Fiction?" He surveyed the research up to that date and concluded that oxygen narcosis is of no significance to recreational divers. Another diver has just stated that the doctor has confirmed that his article is still current.

I would like to ask an expert if there is anything to add to this conclusion.

Boy….careful what you ask for…….


It is clear that it is not clear. There are some intelligent thoughts and theories from both sides.

In my opinion, those who usually dive deeper have likely developed a reasonable tolerance to narcosis, and at depths when it would really matter, significant amounts of extra oxygen can’t be added anyway to replace the nitrogen. So the debate is moot for them. The only ones that it would matter to (as far as divers go anyway), would be anyone noticeably affected at shallower depths who switch to EAN > 21%. If it reduces narcosis then, great for them. I’d be greatly interested in hearing from anyone who is severely affected by narcosis at depths of say 80-90 feet, and who feels (actual and not imaginary) significant changes in narcosis when using high O2 mixes vs. air. (not tri-mix which is apples and oranges).

I guess until the jury comes back with proof one way or the other, we have to go by what works best for us individually. If you Doctors can’t conclusively prove it one way or the other, I sure am not going to try.

Thanks to all contributors. (I think I’ll now go scoop up my brain that leaked out of my ears while trying to follow and comprehend all of this). :wacko:

-Steve

 

[BigJetDriver]

It is clear that it is not clear.

I guess until the jury comes back with proof one way or the other, we have to go by what works best for us individually. If you Doctors can’t conclusively prove it one way or the other, I sure am not going to try.

Thanks to all contributors. (I think I’ll now go scoop up my brain that leaked out of my ears while trying to follow and comprehend all of this). :wacko:

-Steve

Steve,

I am glad that this subject came up. It has given our readers a real "inside" look at the thinking on this subject.

The good Docs who have posted here represent some of the keenest minds, with tons of experience on the subjects of pressure, gases, and their effects on the human body. Gentlemen, we all thank you!

If I may summarize, our Docs and researchers differ a bit in their thinking on the mechanism of narcosis itself. Nevertheless, all seem to agree that, given the way the body utilizes oxygen, even if, as Dr. Teubner puts it, oxygen is twice as narcotic as nitrogen, there is still no net effect from it. To paraphrase his cogent remark, twice zero is still zero. I stand ready for correction by the learned gentlemn, but feel certain that is an accurate summation.

Again, gentlemen, thank you for your participation.

Rob Davie
Scuba Board Staff

 

[waynne fowler]

Of course, gentlemen, this has NOTHING to do with the fact that you are going from 30% oxygen, 30% helium, which leaves 39% NITROGEN, and 1% exotic gases, to EANX 50/50 which has 49%NITROGEN, and 1% etc. does it?

Of course not, since you have made up your mind already.

What?.. Perhaps you should read my previous posts dude. I don't claim to know anything more then I've read... I've read things that fall on both sides of the camp and don't pretend to hold any mystical knowledge beyond or even equal to that of those that are professionals in the field.

My mind is not made up about anything except... that you seem to get offended if you believe some one to have a differing opinion then you may have. If I have left you with the perception that I wanted to argue with you I apologize, I do not.

Though your observation of the effects I've felt at the gas switch are duely noted and welcome I hope that you are able to add to the conversation without being so blatently condesending.

I will listen to anything.. However I will then draw my own conclusions even if they may lead me to a different conclusion then you have came to.

 

[BigJetDriver]

What?.. Perhaps you should read my previous posts dude.
My mind is not made up about anything except... that you seem to get offended if you believe some one to have a differing opinion then you may have. If I have left you with the perception that I wanted to argue with you I apologize, I do not.

Though your observation of the effects I've felt at the gas switch are duely noted and welcome I hope that you are able to add to the conversation without being so blatently condesending.

Waynne,

As you say, perhaps you should read my previous posts "dude". (Interesting mis-use of the word as it applies to Tejas.)

I am neither offended by your opinion, nor am I trying to be condescending, and would appreciate it if you do not attribute that attitude to me.

Perhaps I should have suggested that the symptoms you experienced could as easily be caused by the increase in nitrogen, not the increase in oxygen. The preponderance of opinion among acknowledged experts in the field would seem to bear out that thought.

I quoted several noted people to bear out my contention. I merely present what appears to be the consensus in the literature on the subject. Sorry if that disturbs you. That is not what I intended.

 

[waynne fowler]

As I said.. I wish no arguement.

If you were not meaning to be condesending then I will again apologize. Perhaps I just interpreted you post as being so. I will make attempts to recolour my perceptions.


I welcome the opinions of the experts and accept that they do know what they are talking about even if others with equally impressive cridentals may disagree.

Regardless I find the debate interesting.

Thank you Doc's & BigJet for all the info.

My apologies to the list for side tracking the conversation.

 

[empressdiver]

I just wanted to say that I really appreciated the input from all the contributors as well. I've learned a lot more here about this subject.