Oxygen Narcosis?

[rcohn]

Hi Dr Deco,

I had a discussion last night with a friend who is being trained to use nitrox mixes to alleviate narcosis. I've heard for a long time that this doesn't work but an online search only turned up the following article from 1996, "Oxygen Narcosis: Fact or Fiction?" by Dr. David Sawatzky,
http://divermag.com/archives/dec96/divedoctor_Dec96.html.

Dr. Sawatzky concludes that since the evidence is inconclusive there is no significant problem. Funny, when things are inconclusive I tend to err on the side of caution, but what do I know? Anyway, do you, BillP, or John know of any more recent research results? Any opinions?

Thanks,

Ralph

 

[Dr Deco]

Ralph:

I can certainly see how this article from Dr Sawatzky might seem a contradiction in terms. I have not personally worked in the field of mechanisms of anesthesia for several decades and must acknowledge that this is not my current field. In my earlier work, questions of oxygen narcosis never arose {Rosenberg, MR Powell. A new physical approach to a theory of general anesthesia.2nd International Biophysical Conference, Vienna, Austria, 1966; MR Powell. The Role of the Noble Gas Series in Molecular Pharmacology, In: A Guide to Molecular Pharmacology-Toxicology, Vol. II. [R.M. Featherstone, ed.], Marcel Dekker, New York, (1973)}. The method of narcotic action is still not known. It can not be chemical with some gases since neon is chemically inert (under biological conditions) and yet it is a good general anesthetic (although expensive). The concentration of carbon dioxide is also important and can be difficult to control as precisely as one might wish.

In general, however, demonstration in a scientific sense is often very difficult. People have, for example, attempted to measure tolerance to, or degree of, pain in a quantitative way but with difficult. Yet we all are aware when we hurt a lot, or just feel bad, or feel a bit off. Narcosis is a similar situation. Considerable effort has been invested in the effects of alcohol because of the prevalence of use, and misuse, in the world in general. Gas narcosis is not nearly so widespread, and money and research studies are not as extensive.

Dr Sawatzky states

The scientific data available do NOT support the conclusion that oxygen is narcotic. They also do not and can not show that oxygen has no narcotic effect. Oxygen might somehow be involved in the entire question of narcosis and performance but it is clearly not more narcotic than nitrogen. The narcotic gases are all chemically inert in the body. In contrast, oxygen is one of the most chemically active substances in nature.

What I hear him saying is that scientific evidence in narcosis is not easy to come by. In general, it requires the ability to produce large changes and, that is not possible in the case of oxygen because of its toxicity. We can not measure the effect to such a fine degree with any quantitative accuracy to date. Therefore, if you can not measure a change, then, in an operational sense, it either is not there or too small to matter.

Finally, divers are able to reliably detect narcosis at partial pressures of nitrogen far less than those required to produce reliable scientific results. Thousands of divers claim that high pO2 nitrox results in less narcosis than air at the same depth.

This implies that often we can tell inwardly what it difficult to measure, and with a higher degree of accuracy. If the quantitative tests can not be made to demonstrate a difference, what about just the internal feeling? He concludes that what he has heard is that divers feel that there is less narcosis when oxygen is substituted for nitrogen in the breathing gas.

So as I see it, the bottom line is that oxygen is certainly not more narcotic than nitrogen and is probably less so . Ergo, "oxygen narcosis" does not exist at the pressures encountered in diving.

 

[BillP]

That's very interesting, Ralph. Thanks for posting the link. I had not read Dr. Sawatsky's article before. No, I don't know of more recent research results. Dr. Sawatsky is correct that Peter Bennett quotes studies from the 60's and 70's to support his view that oxygen has a narcotic effect. In his book "The Physiology and Medicine of Diving" Dr. Bennett says {when discussing results of a study he says shows that oxygen has a narcotic effect}, "This would now seem most likely, with evidence available which indicates that raised pressures of oxygen alone can indeed produce narcotic effects and anaesthesia."

From R. W. Hamilton's chapter in "Bove and Davis' Diving Medicine", "Oxygen probably has about the same narcotic potency as does nitrogen." He quotes Dr. Bennett's 1970 paper on "The narcotic effects of hyperbaric oxygen" and a study from 1990 by Linnarsson & Ostlund, "Does oxygen contribute to the narcotic actions of hyperbaric air?".

It's interesting that Sawatsky would read the same studies and come to different conclusions. He presents an interesting argument. Thanks for bringing it up.

Bill

 

[rcohn]

Dr. Deco and Bill,

As always, thank you for the well informed response. Bill, I must admit I hadn't checked my copy of Bennett (it’s pre-1996 anyway), it has been on my “to read” pile for awhile, hopefully I’ll find time to tackle it this winter. Reading the paragraphs on the effects of oxygen on narcosis didn’t clarify things that much, again different tests seemed to have conflicting results.

Thanks again.

Ralph F. Cohn, Ph.D.