Nitrox Not Helping With Narcosis... It's not making sense.

[redacted]

Are nitrogen and oxygen directly narcotic or must they combine with other elements to become narcotic. I though Narcosis was caused by nitrous oxide (N2O) and not directly by nitrogen (N2). Actually, I am somewhat surprised that helium dilution of breathing gas is so effective at combating narcosis.

 

[Rhone Man]

Our knowledge of the physiology of narcosis is imperfect. Most people equate narcotic properties of gases with their lipid solubility. Whilst there seems to be a pretty good correlation, that doesn't seem to be the absolute answer. For instance, it is not clear how the bodies ability to metabolise oxygen may affect its relative narcotic properties (if metabolism had no effect then oxygen would be expected to be 1.7 times as narcotic as nitrogen, which doesn't appear to be the case, although most evidence is purely anecdotal).

But even if you assumed that oxygen was only 25% as narcotic as nitrogen (huge leap, but bear with me), then switching from a 21% oxygen mix to a 32% oxgen mix is not going to create a massive difference to your air-equivalent narcotic depth.

Good summary for further reading: Nitrogen narcosis - Wikipedia, the free encyclopedia

 

[debajo agua]

How narcotic is O2? After doing some research on the net, I found opinions vary. Even though it is more soluble in Lipids, it must also be taking into account, that it's a metabolic gas, whereas, N2 is not. So even though it's more readily absorbed through the cellular wall, it's being used by the cells.

My reading indicates that the magic number for N2 narcosis seems to be ppN2 of 3.4 or thereabouts. What is it for O2 narcosis? It has been said that a diver would suffer a grand mal seizure before feeling O2 narced. Is that correct? Perhaps a hyperbaric tech can provide us some details: Do hyperbaric patients on O2 feel a state of euphoria in the chamber? Do they get narced or do they seize first?

What about the divers here? Do they feel more clear-headed on nitrox than air?

 

[Dive-aholic]

We are only using about 5% of the inspired oxygen. 16% goes back out into the atmosphere on exhalation. So even though O2 is metabolic, it's a minimal amount that is being used. I teach my decompression students to treat nitrogen and oxygen as being equally narcotic. So when we figure out our equivalent narcosis depth we base it on that premise. Helium is about 1/10 as narcotic as nitrogen so for the purposes of recreational diving (meaning to the depths outlined within agency standards or down to 330'), we just don't put it into the equation (although some people do). We go into it in a lot more detail in class but this should be enough for this discussion.

As for chamber rides, it's not really equivalent. People can go way beyond 1.6 ppO2 in a dry chamber without seizing. It's the harsh environment of water, cooler temps, exertion, etc, that makes us more susceptible to seizing at a ppO2 just above 1.6.

 

[MegaBMan25]

There is a personal threshold for getting narced, jut like there is for getting buzzed. Just because you are using EANx doesn't mean you won't , or that it will definitely decrease chance of getting narced. As stated in a previous post, there is inconclusive evidence either way. It is possible to get narced at 40ft on a dive that you have never gotten narced on before. each dive and person should be treated as such that it is possible to get narced, and to know the signs and symptoms and adjust the dive to alleviate the effects.

I.e. - you can get just as narced using Nitrox as you can on regular air in the cylinder

 

[mala]

Can someone please explain to me, why a diver using a gas mix of EANx, won't help reduce the susceptibility to Nitrogen Narcosis?

According to Dalton's Law, it all seems very simple: less N2 into cells = less risk of getting N Narcosis.

My cert. agency sights "inconclusive evidence" and "Oxygen Narcosis" as off setting factors but they didn't offer any more information. I've never heard of anyone getting narcd off O2, if it was possible, I'm sure it would would be a worldwide epidemic. Are the agencies referring possible hyper-ventilating like effects to the body (e.g. dizziness, tingling) from breathing EANx. If so, It was never mentioned to me as a problem breathing EANx. What's going on here?

Unless I'm mistaken, isn't one of the purposes of using Trimix to remove Nitrogen, and replace it with another inert gas, for the purpose of maintaining a clear head at depth? Can't EANx play the same role?

Help me make sense of it all.

TIA

the susceptability for getting narked is the same.
its the depth thats different.

 

[Cave Diver]

Helium is about 1/10 as narcotic as nitrogen

While I don't doubt that (from personal experience) do you have a source for that figure? All the estimates I've seen show it as about 1/4 as narcotic, although I'm not convinced of the real world accuracy of that figure.

 

[mala]

How narcotic is O2? After doing some research on the net, I found opinions vary. Even though it is more soluble in Lipids, it must also be taking into account, that it's a metabolic gas, whereas, N2 is not. So even though it's more readily absorbed through the cellular wall, it's being used by the cells.

My reading indicates that the magic number for N2 narcosis seems to be ppN2 of 3.4 or thereabouts. What is it for O2 narcosis? It has been said that a diver would suffer a grand mal seizure before feeling O2 narced. Is that correct? Perhaps a hyperbaric tech can provide us some details: Do hyperbaric patients on O2 feel a state of euphoria in the chamber? Do they get narced or do they seize first?

What about the divers here? Do they feel more clear-headed on nitrox than air?

recreational limit is 40m
n2 is 3.95 pp02

 

[Dive-aholic]

There is a personal threshold for getting narced, jut like there is for getting buzzed.

This isn't exactly accurate. Narcosis affects everyone the minute you submerge yourself. Even at 10' you are affected by narcosis. If we could get instruments that could record response time in milliseconds underwater we would see this. The "threshold" you refer to is more accurately described as awareness. Some people are more aware of narcosis effects at shallower depths than others. I used to think I hadn't been narced until the first time I realized I was narced. Then the realization of all the times I was narced prior to that came to me. When I taught AOW I brought my students to 80' and gave them a simple math problem to do. Over 90% of my students stated they didn't feel narced but 100% of my students took longer to do the math problem underwater than on the surface and 100% of them failed to follow the exact plan as discussed during the 3 pre-dive briefings we had. So everyone is narced at depth. Some of you just don't realize it...

---------- Post Merged at 01:07 PM ---------- Previous Post was at 01:07 PM ----------

While I don't doubt that (from personal experience) do you have a source for that figure? All the estimates I've seen show it as about 1/4 as narcotic, although I'm not convinced of the real world accuracy of that figure.

I'll have to look for that source but it makes perfect sense to me since He is 1/10 the weight of N2.

 

[Rhone Man]

I'll have to look for that source but it makes perfect sense to me since He is 1/10 the weight of N2.

I don't think that weight is the correct measure of narcotic potency.

Neon is even less narcotic than Helium, despite being heavier. And CO2 is thought to be about twenty times as narcotic as N2 even though it is almost identical in weight.