Diving "Conservative" vs Nitrox

[boulderjohn]

Thanks for the add John. Not much additional to contribute; Neal Pollock and Richard Harris sum it up pretty well in the DAN article. I'm not aware of any peer-reviewed literature that compares increasing computer conservatism with breathing EAN for the same dive profile. Changing gradient factors adds another dimension to this question and makes it even harder to study. Some studies that have been done since the 2014 DAN article, for what they're worth:

A 2020 study that used 40% nitrox, possibly one of the ones that @boulderjohn mentioned with a relatively small n (13):

Does oxygen-enriched air better than normal air improve sympathovagal balance in recreational divers?An open-water study - PubMed

Effects of the hyperbaric environment on the autonomic nervous system (ANS) in recreational divers are not firmly settled. Aim of this exploratory study was to (1) assess ANS changes during scuba diving via recordings of electrocardiograms (ECG) and to (2) study whether nitrox40 better improves...

pubmed.ncbi.nlm.nih.gov

A 2016 study on divers who bubble a lot, which should be interpreted in the context of the study on the high degree of variability in venous gas emboli cited by Dr. Mitchell in another recent thread:

Enriched Air Nitrox Breathing Reduces Venous Gas Bubbles after Simulated SCUBA Diving: A Double-Blind Cross-Over Randomized Trial - PubMed

ISRCTN 31681480.

pubmed.ncbi.nlm.nih.gov

Best regards,
DDM

Thanks for this, but you may have missed the reason you were summoned. Starting t post #54 and continuing here and there is a discussion about both blood oxygen levels and hyperbaric oxygen treatment.

 

[duke dive medicine]

Thanks for this, but you may have missed the reason you were summoned. Starting t post #54 and continuing here and there is a discussion about both blood oxygen levels and hyperbaric oxygen treatment.

Thanks John. I'm not 100% sure of the question but FWIW, dissolved oxygen does play a significant role in hyperbaric oxygen therapy. This was discussed in this thread. Increasing the inspired partial pressure of O2 will dissolve more O2 into the bloodstream. Breathing nitrox does just that as compared to compressed air, but it's not the same as breathing 100% O2 at hyperbaric treatment pressures.

Best regards,
DDM

 

[Blackcrusader]

When I go diving I am usually doing 3 day dives and a night dive. On a two week vacation of 12 diving days I do around 40 plus dives. SO that's 12 days straight diving. I am not pushing NDL's all the time but I do when I want to get video or photo's and pigmy seahorses often around 30m plus so Nitrox is better for extended NDL.

Depending where I am diving I am often doing 75 - 90 minute dives. If I do a trip on air I feel no different to doing the dives on nitrox.
Also on my dives I like to come up shallow and spend 15 mins around 8m or less dawdling around reefs. When I dive like this my mind is blank and I really slow down my breathing as I am so relaxed.

Last trip in Bali all dives on Nitrox and only a few dives to around 30m. I know that often my guide is on a Suunto and one thing is by the third dive I may stay around 25m for most of the dive. The guide can't stay with me as I am using 45/95GF on my Perdix. So I get some quiet time to go really slow to the point of just stopping sometimes at one place for several minutes.
In my 60's and find younger people are tired trying to match my dive schedule. But then they want to party late at night and get on the booze. I am back in my hotel room by 9pm and might do some checking of the days video and photo's for an hour. Up at 7am for breakfast and I eat well. I get a good nights sleep from diving.

Air or nitrox.. always feels the same to me.

 

[dfad]

A beginner's question. Aren't we able to consume less nitrox than air under the same load?
I've never tried nitrox, but I checked various sources and all they state that nitrox can't make shallow dives longer. However, per my understanding, if a body requires some amount of oxygen to support definite activity, and this amount could be taken from more "concentrated" gas mix, this should allow a diver to breath longer on the same amount of nitrox than air. Just breathe less but get the same amount of oxygen, right?
So, what's wrong with this logic? Not kidding or trolling, I'm a beginner as I wrote and I try to understand how it really works.

 

[inquis]

Just breathe less but get the same amount of oxygen, right?

That would work if breathing was driven by the need for oxygen, but that's not the case. It's the elimination of CO2 that drives the impulse to breath, so breathing nitrox just throws away more oxygen molecules on the same sized breath. The benefit of nitrox is that there are fewer nitrogen molecules per breath, so they aren't absorbed by your tissues as rapidly, translating to a longer NDL time compared to air.

For shallow dives, dive time is typically limited by the gas quantity rather than hitting the NDL, so dive time is the same for nitrox and air. The benefit of nitrox in this case is a larger safety margin (lower tissue loading).

 

[justinthedeeps]

Couple of notes/ideas on this apparent thread revival:

ppO₂ is already up to 0.63 atm at 20 metres on compressed air. Not really fair to assume nitrox (32%) "feels better" just because of the elevated oxygen pressures. Air also has that.

Nitrogen also affects cell and neural membranes, due to lipid solubility etc. Which is why we get narcosis. There could be neurological/neurochemical hangovers from high nitrogen exposure, in addition to just raw physical effects of bubbles. Then again, nitrogen bubbles in the brain circulatory system alone also already sounds capable of causing bulk effects of varying severity.

Most of us tend to be healthier and feel better on reduced (or no) alcohol content, especially during recreational activities. Likely the same for nitrogen content in the gases. Probably going to feel healthier overall playing a whole nine innings of baseball drinking NA "beers," than to have beer every inning and quit on the fifth. (YMMV)

 

[tridacna]

The advantage of Nitrox is less nitrogen not more oxygen. Even in standard air, we get more O2 than we can use. We just breathe out what we can’t utilise. Same as Nitrox. The volume per breath is similar so the tank will last the same regardless of mix.

 

[NW Dive Dawg]

Ok....so let's work through this factually, logically and scientifically.

• Breathing O2 on the surface helps to alleviate hangover symptoms.
• Divers on vacations to tropical resort destinations tend to have packages that include Nitrox (usually 32%)
• Divers on vacations to tropical resort destinations tend to drink more than normal and therefore get more hangovers.
• Breathing the increased O2 helps with the hangovers and so the diver feels better in general and attributes this to breathing Nitrox rather than Air.

VOILA!!!!!

 

[FreqFlier]

There is no magic elixir in nitrox that makes you "feel" better.

The "magic elixir" in Nitrox is a lower N2 content. Doesn't really make much difference in a single, relatively shallow dive (50-60' or less), but makes a serious dent in your NDLs and SI's during multiple consecutive, deeper (50-110') dives.

 

[Mobulai]

If I constantly have headaches every day and I just take motrin and never try to figure out why I'm not sure motrin is really an answer... to me it's just a "band-aid"?

This thread has probably run its course, and others far more knowledgeable than me have already covered everything else, far better and more eloquently than I ever could.

I wanna address this specific part — i get your sentiment, and I don’t disagree with the one part about 1 air dive > fatigue > something is a miss and has to be fixed, and how nitrox can feel like a band aid instead of addressing the issue.

But I gotta say (just my 2 bubbles) it’s dangerous using that metaphor, because it would ve getting cause, effects, symptom and „pathos“ in the wrong order (and it might seem a bit counterintuitive):
Using nitrox addresses the (not necessarily root) cause of the symptom (fatigue): N2 loading
Slow*er* ascent, more conservative profiles, etc. would be mitigation of the symptom, the ailment, the high saturation of n2 in tissues, that already happened (be that on air, nitrox, doing a long deco dive…)

Nitrox is not having 10 cups of coffee to prevent that headache from occurring in the 1st place in that case, not the motrin/advil

I’m thinking here from the POV of the body, but probably I’m getting lost in some philosophical sauce here
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For sure, if it’s simply not just your physiology that you have lo tolerance for N2, then just throwing nitrox at it keeps you from achieving your potential, having longer profiles than what you can handle now
From the pov of the divers aptitude and achieving their potential, yes, band aid works (back on my philosophical BS)

But what happens if not? That’s as good as you can handle on your best day?
Nitrox for sure comes to the rescue

edit: if someone can actually „mark“ that threshold/transition between it working or not, you probably could (in theory) have your very own deco algo tuning (human factors whatever)
PS: not instructions, not a doctor, not a dive pro, just a dude who like to code models and think about them — please don’t hurt yourself
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Thanks for starting such an interesting thread btw