Nitrox - Is it "worth it"?

[kelemvor]

Current thinking is that oxygen is as narcotic as nitrogen or even more so. Nitrox does not reduce narcosis. If you feel less tired, congratulations. The placebo effect works for you. There is no scientific evidence that backs up your claim.

Actaully, there is scientific evidence of that very thing - as has already been discussed. Evaluation of critical flicker fusion frequency and perceived fatigue in divers after air and enriched air nitrox diving. - PubMed - NCBI

RESULTS:
The two groups were comparable in sex ratio, age and diving experience. The change in perceived fatigue level after a single dive was significantly lower when EANx was breathed compared to air dives (VAS; P < 0.001). Compared to pre-dive, CFFF decreased by 6% in the air group (P < 0.01) but increased by 4% in the EANx group (P < 0.05). The post-dive difference between the two groups was highly significant (P < 0.001).

 

[rjack321]

For recreational diving, I am convinced nitrox is a good thing. (Just ask @Wookie about the nitrox vs. air bends on the Spree.)

Mike Lever on the Nautilus Explorer has the same stories.
Diving EANx on air tables or close to air tables makes a whole lot of sense even at 1 or 2 dives per day when you're remote.

 

[scubadada]

I often push my NDLs to the same point whether I am diving air or nitrox. I believe my risk for DCS is the same with either gas. I just get to dive longer on nitrox

 

[scubadada]

Actaully, there is scientific evidence of that very thing - as has already been discussed. Evaluation of critical flicker fusion frequency and perceived fatigue in divers after air and enriched air nitrox diving. - PubMed - NCBI

@kelemvor

I do not have access to the full article for details. It appears that the air and nitrox divers had dives of the same depth/duration so that their nitrogen exposures would have been significantly different. I do not understand critical flicker fusion frequency well enough to know how it relates to fatigue. It is my impression that it is a reflection of central nervous system processing rate, of a visual stimulus, in this case

 

[TrimixToo]

I often push my NDLs to the same point whether I am diving air or nitrox. I believe my risk for DCS is the same with either gas. I just get to dive longer on nirrox

For the reason I posted in #116, I am not certain your risk is the same either way even if you hit the NDL on both. I think it's likely lower on nitrox. (Can I prove it? Well...no. But go ahead and tell me how I'm wrong, if I am.)

 

[CaptainPanda]

A related question: how much more worth it is a nitrox certification class than if you take a nitrox adventure dive? What more do you learn in the class that makes a certification class worth the cost?

 

[scubadada]

For the reason I posted in #116, I am not certain your risk is the same either way even if you hit the NDL on both. I think it's likely lower on nitrox. (Can I prove it? Well...no. But go ahead and tell me how I'm wrong, if I am.)

I ran a few profiles on air, 32%, and 36%, essentially up to NDL. You are correct, the nitrogen loading at the surface is highest for air, lowest for 36%.

 

[BRT]

I ran a few profiles on air, 32%, and 36%, essentially up to NDL. You are correct, the nitrogen loading at the surface is highest for air, lowest for 36%.

Why is that? Better offgassing on the ascent?

 

[markmud]

You might ask Wookie what his experience was on his dive boat. I believe that once he started pumping nitrox for everyone he never had another DCS case.

I followed your advice and did ask @Wookie about his experience onboard Spree regarding EANx. It is staggering--albeit anecdotal--staggering nonetheless.

For the reason I posted in #116, I am not certain your risk is the same either way even if you hit the NDL on both. I think it's likely lower on nitrox. (Can I prove it? Well...no. But go ahead and tell me how I'm wrong, if I am.)

My tech instructor used the term "washout" in describing O2 in decompression gasses. The higher the O2 (always avoid the CNS hit) the better the gas worked to washout nitrogen. As you descend on nitrox, you are shaving the odds by eliminating a little bit more nitrogen on every breath than you would on 21%.

I ran a few profiles on air, 32%, and 36%, essentially up to NDL. You are correct, the nitrogen loading at the surface is highest for air, lowest for 36%.

In tech 40 we did the same thing. Theoretically it worked.

Again to the OP, get the Nitrox cert and just pay for the EANx upcharge. It is an insurance policy. Is it a huge policy? No, but you are ever so slightly shaving the odds on every dive.

In recreational profiles it is very difficult to exceed the O2 exposure window. It can be done but difficult. To the point that my tech instructor told me not to track my 02 exposure for the type of diving I do.

cheers,
m

 

[scubadada]

Why is that? Better offgassing on the ascent?

That appears to be the case. In each instance, the nitrogen load when arriving at the safety stop and when arriving at the surface is less for nitrox compared to air. It would seem this would be demonstrable comparing SurfGFs

I don't know if these differences make a practical difference in the risk of DCS when diving close to the NDL and making a standard safety stop. On a theoretical basis, it would seem possible