Nitrox: Narcosis myth?

[rongoodman]

I think it comes from the term nitrogen narcosis itself. They should have used a different term such as air narcosis. It's like when reporters use the term oxygen tanks when they mean air or mixed gas.

I usually see it referred to as inert gas narcosis.

 

[uncfnp]

According to the Meyer-Overton theory that is generally accepted for narcosis, oxygen should be more narcotic than nitrogen. The problem is that some (not all) of it is metabolized through breathing. Almost all people assume that there is no difference between nitrox and air in terms of narcosis. The problem is that although you can test for nitrogen's effect in a chamber by maximizing the dose, you can't do it with oxygen because of toxicity, so it remains an assumption.

If oxygen is about the same as nitrogen, then the partial pressure required for narcosis on nitrox would be about the same as for air. That means that a tech diver doing decompression on EANx 50 at 70 feet would expect the same narcotic effect as a diver diving air at 70 feet--not much.

Sorry Boulderjohn. I typed nitrogen but was thinking oxygen. I've corrected my typo. Must be narced.

 

[MaxBottomtime]

I usually see it referred to as inert gas narcosis.

Even that is incorrect. Oxygen is not an inert gas.

 

[northernone]

I usually see it referred to as inert gas narcosis.

That's a common term too I hear instructors use if they don't use nitrogen narcosis. Again, perhaps an incomplete picture as that would exclude o2 and co2 which are both far from inert and are highly narcotic at depth.

(Since realising we've developed our own definition of an inert gas separate from the scientific definition. Curious though because it's still referred to in the research as "
Gases that are metabolically inactive")

 

[boulderjohn]

Even that is incorrect. Oxygen is not an inert gas.

Technically, it is not an inert gas. However, only a very small percentage of it is metabolized while diving, and so in terms of narcosis it is treated as an inert gas. The definition used is different from the one used in chemistry classes. In chemistry classes, nitrogen is not an inert gas, either.

 

[northernone]

Technically, it is not an inert gas. However, only a very small percentage of it is metabolized while diving, and so in terms of narcosis it is treated as an inert gas. The definition used is different from the one used in chemistry classes. In chemistry classes, nitrogen is not an inert gas, either.

Perhaps an interesting read from 1966...

http://pmj.bmj.com/content/postgradmedj/42/488/378.full.pdf

 

[Patoux01]

The definition used is different from the one used in chemistry classes. In chemistry classes, nitrogen is not an inert gas, either.

My understanding is that we talk about biology/physiology. Inert in that sense means your body can't do anything with it, it comes in and it comes out the same. Like gold or titanium are inert in the human body, hence they could be used for teeth and prosthesis.

As for Nitrox and narcosis, it comes up every other day in France where the deep air guys explain that "you get less narcosis on Nx24 than on Nx21, I can feel a huge difference". Had to deal with it 10 days ago... I suspect at least some nitrox instructors teach that there.

Diver 1: I consider it safer to go 40m on Nx28 than on air. I might be on higher PO2, but at least I won't be narced!
Me: Nitrox has no influence on narcosis as far as we know.
Diver 2: Technically, there's less nitrogen, so less narcosis. It might not be a huge difference though...
Me: *quits*

Interestingly, it's on a facebook group about diving accidents and prevention, so you can get the "like" ratings. They went 4-2-2 (diver 1, me, diver 2), which imo suggests most people believe nitrox will help prevent narcosis.


I believe there's a few studies saying it does reduce narcosis, can't get my hands on them (supposed to be working right now ), so someone else might get them. Last one I have seen is Impairment from Gas Narcosis When Breathing Air and Enriched Air ...: Ingenta Connect which goes in the sense that it doesn't matter.
Personally, in the absence of irrefutable proof that nitrox helps narcosis, I'll go on the safe side and not consider it to reduce narcosis.


You can find this kind of claims in slides from courses like http://subaplongee.free.fr/Nitrox/Cours nitrox SUBA.pdf (french, slide 6, no idea how old that thing is), http://www.rcae-plongee.be/documents/Cours/Nitrox/Nitrox de base_cours.pdf (french, but from belgium, slide 28) and in other courses I simply don't get any hit when searching through the documents with "narcose". This suggests to me that it's either said orally, or not mentioned at all. If it's not mentioned, that could explain why people believe nitrox helps narcosis, because "it's evident, there's less nitrogen".


Part of the issue could be that divers looking for info stumble upon this kind of information like I did. Like I said, I have no idea how old those pdfs are, but they're still around on the interwebz, along with a whole bunch of others.


Edit: http://www.ctd69.fr/download/fichier/000072/cours_nitrox_jean_marcilly.pdf so it was taught still in 2010. I'm really starting to hate those people that won't write the date of when they wrote their stuff.

 

[Trace Malinowski]

Is Oxygen Narcotic? by Martin Robson

 

[NAM001]

Nowhere an expert here. If N2 brings on narcosis in a range from 3.5 to 4.5 PP. what PP's are needed to make O2 bring on narcosis?

The reason is that I have had divers take pictures at 120 ft on air and they don't remember taking them. On nitrox that symptom did not exist on that diver.

It made me wonder if time was also a factor in O2 becoming narcotic along with pressure and FO2. It was a topic questioned when I took my trimix class at the introduction of END. The question made since to ask given we were diving doubles for the class.

I just read the prior post and if I read it right it said that O2 and N2 both being narcotic under the same PP.

 

[RainPilot]

Here's a thought experiment (i.e. all numbers are made up)

Lets say N2 becomes noticeably narcotic at a PP of around 3 bar (air at 30m)
Lets say O2 becomes narcotic at say 1.6 bar. (twice as narcotic)

Diver at 30m on air has N2 at 3 bar causing narcosis, O2 is at 0.84 so no effect yet.
Same diver on 30% has O2 at 1.2, causing little to no narcosis. N2 is at 2.8 so no N2 narcosis.

The big question would be if narcosis is cumulative i.e. add O2 effect and N2 effect or whether they are acting separately.

The same way we treat He and N2 separately with deco, does that translate to the narcotic effects?

Please FTR, I am NOT arguing either side, I genuinely don't know enough about the mechanisms of narcosis when it comes to separate gases to even guess.

Maybe @Dr Simon Mitchell can give us a professional opinion as an anesthesiologist ?