Nitrox: Narcosis myth?

[northernone]

Addressing a myth here.

When people hear I dive air I've had at least 20 in the last year recommend nitrox (among other excellent reasons) for a clearer head or being less narced due to less nitrogen. There's a half dozen recent posts online suggesting the same.

Why is this still so prevalent? We talk of gas narcosis in training and yet I'm surprised how often among fellow divers I'm hearing about nitrox having trimix effects for reducing 'Nitrogen narcosis'. Are shops overselling the benefits of nitrox? Or is it an older belief that's been debunked? Had a rather insistent discussion with a fellow instructor who was convinced of that nitrox benefit.

In unscientific testing I've switched from low o2 to high o2 content gas at depth, nitrogen making up the rest. Mental clarity didn't improve doing math on my slate. Switched to lean trimix and immediately cleared up the cobwebs. Gas density eased the breathing and helped co2 retention too I suspect as well as less narcotic gasses in the mix.

Regards,
Cameron

 

[KevinNM]

Oxygen is as or more narcotic than nitrogen.

 

[Scott]

I believe it's just people not fully understanding, not paying attention or are just ignorant.
Nitrox = less nitrogen than air = less narcosis. I've had similar conversations with people and a few students will ask the question during a nitrox course.
Just clear up the misinformation and move on.

 

[Caveeagle]

I have a couple dives that I do semi-regularly where I am at the 90-100' level for 25-40 minutes. I have noticed more of a mild "buzzed" feeling when diving 32% Vs similar Dive profile on 21%.

Just a anecdotal comparison, but since Dive profiles tend to be somewhat consistent for me, it tends to validate that elevated o2 can increase the narc

 

[boulderjohn]

The idea comes up from time to time on ScubaBoard, but it is pretty rare. The only two agencies for which I have taught nitrox do not teach that it reduces narcosis, and I don't know any agency that does. I don't know anyone who teaches that officially, so I would not blame it on anyone teaching it for any nefarious reasons.

Outside of the handful of ScubaBoard arguments, I have never heard anyone argue that point. You must be meeting some unusual people.

 

[northernone]

The idea comes up from time to time on ScubaBoard, but it is pretty rare. The only two agencies for which I have taught nitrox do not teach that it reduces narcosis, and I don't know any agency that does. I don't know anyone who teaches that officially, so I would not blame it on anyone teaching it for any nefarious reasons.

Outside of the handful of ScubaBoard arguments, I have never heard anyone argue that point. You must be meeting some unusual people.

Glad to know it, thanks.

And yes, we're an eclectic bunch of divers! I've been 9 months in the past year as an average jo shore diver in the Caribbean over the winter (besides CCR and cave diving) and been meeting a ton of dive shops trying to upsell nitrox fills and chatting with random vacation divers I encounter.

 

[MaxBottomtime]

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.

 

[uncfnp]

Could someone please link the relevant research on this? I read about the narcotic effects of oxygen but have yet to see the research. At what partial pressure of oxygen does this occur? I must be missing something since I never hear of technical divers narced on thier deco stops.

 

[boulderjohn]

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.

PADI no longer calls it nitrogen narcosis for that reason.

 

[boulderjohn]

Could someone please link the relavant research on this? I read about the narcotic effects of nitrogen but have yet to see the research. At what partial pressure of oxygen does this occur? I must be missing something since I never hear of technical divers narced on thier deco stops.

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.