It would be so much fun if we could scientifically attribute using Nitrox as the isolated factor. Seems there was a lot of "progress" in the dive community during this same time period. Computers got faster processors, tables became essentially ignored, big training pushing the oxygen enriched mixes, so I think it's fair to say the way divers approached dive execution morphed as a whole. But very interesting regardless...
Nitrox extends NDL but does it have other benefits?
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It would be so much fun if we could scientifically attribute using Nitrox as the isolated factor. Seems there was a lot of "progress" in the dive community during this same time period. Computers got faster processors, tables became essentially ignored, big training pushing the oxygen enriched mixes, so I think it's fair to say the way divers approached dive execution morphed as a whole. But very interesting regardless...
The good news about Nitrox is less nitrogen in each breath. This is formally the same as diving to a lesser depth, hence the Equivalent Air Depth concept.
As to being tired:
1. I definitely know I am less tired after a nitrox dive than after an equivalent air dive....even for just a couple of dives, especially if the dives are a bit deeper (but within my nitrox MOD). I know this from having done essentially the same dive many times, both with air and with nitrox. I have almost 2000 dives, so my statistics are pretty good. The effect is *most* noticable on a several-dives-a-day dive trip, especially liveaboards. [Recently on the Kona Aggressor only two of us got the Iron Man award for having done ALL the dives; he was the youngest, I was the oldest.] On several-dives-a-day shore dives (think Bonaire) the logistics introduce their own tiredness factor, which can be dominant.
2. Most of my trips are group trips, with somewhat older divers. Many of them have switched to nitrox (I offer the class free to folks on my trips) and ALL of them in the older category report back to me that they are not as tired. It is only the younger, fitter, smaller BMI folks who tell me they can't feel any difference.
3. I am never tired after a technical dive with proper deco and lots of O2 at the end. This is true whether the dive was on air, light nitriox, or trimix....but ALL of them have high-percentage nitrox or pure O2 at the end.
So I subscribe to the "subclinical DCS" school of thought as to the source of my tiredness. And I find it on the fine line between funny and irritating that some people refuse to believe I am less tired simply because *they* are less tired, and/or they cannot quote proof that the less-tired effect exists.
As to being tired:
1. I definitely know I am less tired after a nitrox dive than after an equivalent air dive....even for just a couple of dives, especially if the dives are a bit deeper (but within my nitrox MOD). I know this from having done essentially the same dive many times, both with air and with nitrox. I have almost 2000 dives, so my statistics are pretty good. The effect is *most* noticable on a several-dives-a-day dive trip, especially liveaboards. [Recently on the Kona Aggressor only two of us got the Iron Man award for having done ALL the dives; he was the youngest, I was the oldest.] On several-dives-a-day shore dives (think Bonaire) the logistics introduce their own tiredness factor, which can be dominant.
2. Most of my trips are group trips, with somewhat older divers. Many of them have switched to nitrox (I offer the class free to folks on my trips) and ALL of them in the older category report back to me that they are not as tired. It is only the younger, fitter, smaller BMI folks who tell me they can't feel any difference.
3. I am never tired after a technical dive with proper deco and lots of O2 at the end. This is true whether the dive was on air, light nitriox, or trimix....but ALL of them have high-percentage nitrox or pure O2 at the end.
So I subscribe to the "subclinical DCS" school of thought as to the source of my tiredness. And I find it on the fine line between funny and irritating that some people refuse to believe I am less tired simply because *they* are less tired, and/or they cannot quote proof that the less-tired effect exists.
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Going back to the original question about the "How stuff works" article: The article is correct. If the blood oxygen level falls sufficiently, what's called the "hypoxic drive" will kick in and stimulate breathing. It's a weak drive and only functions at life-threatening levels of hypoxia. Under normal, day-to-day conditions in healthy individuals, the only drive that is affecting the volume passing through the lungs is CO2 (and, of course, anxiety 
).
There is some evidence to suggest that people breathing EAN may permit slightly elevated CO2 levels, which WOULD affect their SAC rate. The effect is small.
I am personally convinced that I feel better diving Nitrox, and I also harbor a small, personal suspicion that I'm more narced on air, although there is neither any experimental evidence to support that, nor is there any theory that would suggest it. And my reduction in narcosis came with increased diving experience as well as the change to Nitrox, so either could be the reason. I haven't wanted to experiment to find out.
). There is some evidence to suggest that people breathing EAN may permit slightly elevated CO2 levels, which WOULD affect their SAC rate. The effect is small.
I am personally convinced that I feel better diving Nitrox, and I also harbor a small, personal suspicion that I'm more narced on air, although there is neither any experimental evidence to support that, nor is there any theory that would suggest it. And my reduction in narcosis came with increased diving experience as well as the change to Nitrox, so either could be the reason. I haven't wanted to experiment to find out.
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On a typical two tank dive recreational dive day, I feel just fine when I am done, regardless of what I am breathing. If I feel fine breathing air, how am I going to measure if I might feel better breathing nitrox? The only study I ever saw was set up that way. They asked divers to do two easy dives with a good surface interval to see if they felt any difference.
Here is my anecdotal evidence of a more severe test situation.
Before I was nitrox certified, I did a three day liveaboard trip in Australia, doing 3 dives the first day, 5 dives the second day, and 4 dives the third. I was dead tired each night and went to bed early. The third night I was in bed before eating dessert, and if you know me, that is saying a lot. I slept close to 12 hours.
Since then I have done three liveaboard trips, each with 6 days of diving averaging 4 dives per day, each one using nitrox. On every one of those evenings, I felt great socializing with everyone else until a normal bed time. I never once felt the compulsion to go to bed early.
I think you need to set up something like that to get a sense of the difference. I don't think a two tank dive day can tell you a thing.
Here is my anecdotal evidence of a more severe test situation.
Before I was nitrox certified, I did a three day liveaboard trip in Australia, doing 3 dives the first day, 5 dives the second day, and 4 dives the third. I was dead tired each night and went to bed early. The third night I was in bed before eating dessert, and if you know me, that is saying a lot. I slept close to 12 hours.
Since then I have done three liveaboard trips, each with 6 days of diving averaging 4 dives per day, each one using nitrox. On every one of those evenings, I felt great socializing with everyone else until a normal bed time. I never once felt the compulsion to go to bed early.
I think you need to set up something like that to get a sense of the difference. I don't think a two tank dive day can tell you a thing.
There was a study performed to try and measure the effects of nitrox on diver fatigue. The study concluded that nitrox didn't do much for fatigue. I feel like it makes a difference when I dive. Perhaps it's just perception, but even if that's true it's worth diving to me.
It's worth noting that the study had a handful of flaws (noted in the study document). One such flaw was that it was performed in a chamber rather than on actual dives. Maybe that was a factor in the negative results.
It's worth noting that the study had a handful of flaws (noted in the study document). One such flaw was that it was performed in a chamber rather than on actual dives. Maybe that was a factor in the negative results.
There was a study performed to try and measure the effects of nitrox on diver fatigue. The study concluded that nitrox didn't do much for fatigue. I feel like it makes a difference when I dive. Perhaps it's just perception, but even if that's true it's worth diving to me.
It's worth noting that the study had a handful of flaws (noted in the study document). One such flaw was that it was performed in a chamber rather than on actual dives. Maybe that was a factor in the negative results.
This study subjected divers to a chamber dive of about 60 feet for 40 minutes and then tested their fatigue levels. As I said, I don't think that is enough of a stressor to be able to tell a difference.
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And maybe the difference isn't really quantifiable. I think I feel better after a working dive (hydraulic drilling of moorings, etc.) on nitrox than I do on air. I only think this because I don't feel like I need a nap between dives. Purely anecdotal, and I don't run around extolling the recuperative values of nitrox anymore either, because it isn't measurable. But maybe it's a barely measurable effect, but it doesn't take much to make a physiological difference. I've watched as divers running the same dive profiles with slightly different gradient factors bubble like mad following a dive or not bubble at all. The difference in GF is minor, the physiological difference is amazing.
There is something I have always wondered about, and perhaps one of the physicians can explain it to me. My question relates to the similarities and differences between diving on nitrox and hyperbaric oxygen therapy. Here is the Mayo Clinic's explanation of hyperbaric oxygen therapy: Hyperbaric oxygen therapy Definition - Tests and Procedures - Mayo Clinic. In the article, they explain the reason it is done.
The standard thing we say in regard to nitrox is that the additional oxygen provides no benefit in itself--the benefit comes from less nitrogen. I hope someone can explain to me why increased oxygen under pressure provides such a wonderful benefit in hyperbaric oxygen therapy but has no benefit when diving.
The standard thing we say in regard to nitrox is that the additional oxygen provides no benefit in itself--the benefit comes from less nitrogen. I hope someone can explain to me why increased oxygen under pressure provides such a wonderful benefit in hyperbaric oxygen therapy but has no benefit when diving.
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