Nitrox?

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I appreciate the feedback. So far every dive I've done has been pretty simple and the DMs have always looked after the "old, new guy". I've always felt well cared for but understand that I'm responsible for myself and my own safety.

I really have nothing to prove. Dont need to go deeper or longer. I've enjoyed the short, shallow dives as much as any others. 35 mins at 30-40 feet works for me. Hell, I'm just glad to be able to dive at my age.

Oh...and last week in Roatan on a cruise I talked my younger brothers (one is 65, the other 57) into doing a discovery dive while I did my first dive. Then we dived together on the second dive. They of course struggled with buoyancy but it was fun diving with them. They enjoyed it. I've always been the adventurous one in the family.
I think if you just get a cheap wrist computer, that would be fine for what you do. You can get a Mares Puck for probably under $200 and it will give you everything you need including nitrox settings for when you do that.
Slap it on and you’ll have your own personal info screen that you can keep track of instead of relying on the divemaster, and you’ll know in real time what’s going on.
As far as taking nitrox, yes do it, why not? It’s another tool to use. Any further training IMO can’t hurt.
 
2 1/2 years ago I summarized the most-quoted existing research on Nitrox and post-dive fatigue, which at that time was inconclusive mainly for two reasons: (1`) differing definitions of "fatigue" by divers and researchers, and (2) studies that looked at single dives or chamber dives rather than repetitive in-water dives. Aside from various criticisms of methodology and statistical significance, no real conclusions could be drawn at that time. Meanwhile, the anecdotal evidence for lessened fatigue continues to accumulate...

One of the interesting parts of that 6-page thread (disregarding the off-topic diversion about goats) was the suggestion that any perceived 'lessened fatigue)" was not related to the increased O2 in Nitrox, but rather to the lessened N2. In other words, the farther away you are from your NDL on a dive, the better you might feel afterward. Since Nitrox allows you to stay farther away from your NDL -- all other things being equal -- then the apparent lessened fatigue might be just because you have less sub-clinical DCS.

The critical references used in the DAN summaries are:
Chapman SD, Plato PA. Measurement of fatigue following 18 msw open-water dives breathing air or EAN36. In: Brueggeman P, Pollock NW, eds. Diving for Science 2008. Proceedings of the American Academy of Underwater Sciences 27th Symposium, 2008; 1-11.​
This publication is based on a 2007 Master's Thesis, available here.​
Harris RJD, Doolette DJ, Wilkinson DC, Williams DJ. Measurement of fatigue following 18 msw dry chamber dives breathing air on enriched air nitrox. Undersea Hyperb Med. 2003; 30(4): 285-91.​
Lafère P, Balestra C, Hemelryck W, Donda N, Sakr A, Taher A, Marroni S, Germonpré P. Evaluation of critical flicker fusion frequency and perceived fatigue in divers after air and enriched air nitrox diving. Diving Hyperb Med. 2010 September; 40(3): 114-8.​

The DAN article that summarizes this work is mainly an interview with Harris and Doolette:
That article asks, and Harris and Doolette respond:
Are there any reliable data to support claims about nitrox causing less postdive tiredness than air?
Harris: No. Three articles in the peer-reviewed literature (see the first three in the references sidebar) contribute evidence to the nitrox and fatigue question, but I am not convinced that the size and power of any of them have addressed the problem comprehensively.​
Pollock: The data supporting these claims are not compelling. This is not surprising since PO2 increases substantially in response to depth alone. However, there is no reason to argue over whether a person feels less fatigued. Research has shown that the placebo effect has physiological impact, so let the diver enjoy the sense. The important thing is for divers to stay within the PO2 limits to avoid oxygen toxicity.​

Further, on the issue of sub-clincal DCS, they say:
Would you consider tiredness/fatigue a sign of subclinical DCS?
Harris: I believe that fatigue can be a symptom of DCS, but it needs to be something very marked to impress me. Severe fatigue, such as feeling like you have the flu rather than just being “a bit more tired than usual after diving,” is a more serious issue. Rather than use the term subclinical DCS, which I do not favor, I would only call fatigue DCS if it is part of a constellation of symptoms.​
Pollock: Normal patterns of postdive tiredness would not qualify, but “unusual fatigue” markedly in excess of typical levels could be a sign or more likely a symptom. Having the diver describe the nature and degree of the effect is important to help distinguish normal from unusual.​
Despite a common impression that diving on nitrox may cause less fatigue than performing the same dive using an air mixture, scientific research to date has not found solid evidence to support such an assumption. As mentioned, the placebo effect should not be underestimated and has yet to be fully studied.​
No new relevant studies that I can find have been published since those old ones, except for this one:

Fabian Möller , Elena Jacobi , Uwe Hoffmann , Thomas Muth , Jochen D. Schipke. Oxygen-enriched Air Decreases Ventilation during High-intensity Fin-swimming Underwater. Int J Sports Med 2022; 43(03): 230-236.​

Möller et all see a significant decrease in ventilation during strong swimming for divers using enriched air, suggesting there is more going on with Nitrox than just decreased N2 uptake.

Caveat: there are many blogs and books and manuals and divers and instructors and agencies that say enriched air has no effect on fatigue, or that it reduces fatigue. If they give any citations at all, it is usually either the Harris article from 2003 or the DAN summary from 2014, in which Harris disavows his 2003 article as really addressing the issue.

The question is still open.
 
Given the recent articles about O2 likely not being narcotic, there are reasons to believe Nitrox may in fact reduce fatigue. The likely mechanism is that increased PO2 reduces the PN2, and there is good reason to expect N2 to be fatiguing both due to narcotic effects and sub-clinical DCS effects.
 
there is good reason to expect N2 to be fatiguing both due to narcotic effects and sub-clinical DCS effects.
What good reason would that be? Where did you find that narcotic effects also lead to fatigue?
 
What good reason would that be? Where did you find that narcotic effects also lead to fatigue?
Examples of fatiguing "narcotic" effects: alcohol, marijuana, morphine, heroin, hydrocodone, etc.
Basically, all the "depressant drugs". They all often make you feel tired or sleepy.

Also, the times that I have experience nitrogen narcosis specifically, I found experience highly fatiguing. So anything that reduces that nitrogen narcosis would also likely reduce the fatigue.
 
Comparing dry chamber dives at 18 metres to proper scuba dives at 20 to 30 metres in the ocean is not really a valid comparison.
 
Examples of fatiguing "narcotic" effects: alcohol, marijuana, morphine, heroin, hydrocodone, etc.
Basically, all the "depressant drugs". They all often make you feel tired or sleepy.

Also, the times that I have experience nitrogen narcosis specifically, I found experience highly fatiguing. So anything that reduces that nitrogen narcosis would also likely reduce the fatigue.
Nitrogen narcosis goes away if you ascend a bit. Are you saying it gives you fatigue that stays with you?
Comparing dry chamber dives at 18 metres to proper scuba dives at 20 to 30 metres in the ocean is not really a valid comparison.
Another study involved actual dives.
 
Remember that narcosys is often caused by CO2, not by nitrogen. And CO2 is caused by over exertion and poor ventilation.
This makes obvious that after an episode of narcosys which wad triggered by CO2 accumulation one feels tired.
In these analyses one must always take into account several factors which interact in your body.
I liked the Bulhman approach of adapting his deco algorithm to exertion (or effort), as this is a very important factor interfering with nitrogen diffusion through the body.
 
https://www.shearwater.com/products/swift/

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