Nitrox the Wonder Gas

[Wildcard]

Spend some time under water instead of at a computer and you will find the benifits of Nitrox as well as the limitations.
It is not a "magic potion" not advertised as such.
We dive almost daily, repetitive diving and would be crazy not to dive Nitrox with the advantages it supplies.
I think all of you who have a few dives under your weight belts would agree. I also see daily , people want to equate the cost in dollars with the value of Nitrox.
Very foolish - and not worth arguing

Clearly it is. Even doing rep deep dives none ofthe DM/Inst in Hawaii dive EAN that I know of. Deep? Yes 90-125. two or three times plus a few bounces. added in. EAN has it's place but it's not on daily dives to rec limits unless your realy doing four or more a day. Many like to say that but few do.

 

[Charlie99]

It would seem to me that how you feel at the end of a dive is a function of how you decompress, not your breathing mixture. I think we are in an agreement that post dive fatigue is a form of subclinical DCS. Let's work from there.

If you dive nitrox, decompress well (saftey stops, deep stops, acent rate, surface deco, etc), its safe to say you will feel better (which is entirely subjective) than if you didn't decompress well. The same holds true with air diving.

Now, for a given dive within NDLs with nitrox (we'll say 32%), you'll be taking in less nitrogen than for the same dive with air. Make sense?

Diver A is a clone of Diver B. Diver A and Diver B do the exact same dive, same deco...but Diver A is on 32% but Diver B is on air. From this, we can assume that Diver A will feel less fatigued than Diver B.

I'm 100% in agreement until the last sentence.

If it is a low stress dive -- far from NDL; or if to NDL or beyond, then decompressed properly with a proper ascent profile -- neither A nor B will have post-dive fatigue, so therefore nitrox will have no effect. IIRC, the DAN study that concluded "no effect on post dive fatigue" didn't push the limits. If there isn't any signficant DCS-induced fatigue, then there isn't going to be any difference.

 

[Charlie99]

Clearly it is. Even doing rep deep dives none ofthe DM/Inst in Hawaii dive EAN that I know of. Deep? Yes 90-125. two or three times plus a few bounces. added in. EAN has it's place but it's not on daily dives to rec limits unless your realy doing four or more a day. Many like to say that but few do.

But what are the profiles of those DMs? Most of my deep dives in Maui are very much multilevel dives, with lots of shallow time to offgas nicely. Easily done on air. All nitrox would do is to allow me to weight the overall profile a bit more towards the deep side. Not really that much advantage since there's nice stuff to look at all the way from the bottom to the surface.

OTOH, I'll always dive nitrox in SE Florida, where the dives are near square profile, and I need the nitrox advantage to properly offgas before reaching my midwater-hang boredom limit.

 

[cummings66]

I would also say that I've dove air to depths of 100 feet, 5 dives a day to the ndl each time over 3 days. In the beginning I'd feel bad after the second dive, after I learned how to ascend and started doing stops down deeper (another article on Dans site, and DIR supported) then those profiles stopped bothering me. Proper ascents IMO make more of a difference than the mix I breathe.

By the time I got Nitrox certified I had pretty much started coming up better than how I did in the beginning, probably exceeded 60 fpm many times in the start, almost never do now.

So, in the beginning I might have agreed that Nitrox is a wonder gas making me feel better, now I won't say that.

Most of the time by the way I do 5 dives in a weekend.

 

[Wildcard]

But what are the profiles of those DMs? Most of my deep dives in Maui are very much multilevel dives, with lots of shallow time to offgas nicely. Easily done on air. All nitrox would do is to allow me to weight the overall profile a bit more towards the deep side. Not really that much advantage since there's nice stuff to look at all the way from the bottom to the surface.

OTOH, I'll always dive nitrox in SE Florida, where the dives are near square profile, and I need the nitrox advantage to properly offgas before reaching my midwater-hang boredom limit.

I was talking about Oahu, shoulda been more specific. It's all on the bottom. Very square profiles. Still, no one does it. Like the last poster said, asscend very slow and it's all good. OTH if you WANT to spend money on wonder gas and it makes you feel better even if it's only in your mind, go for it!

 

[Diver Dennis]

It's funny to see the hotshots show up flashing there nitrox cards and demanding it's use, then they suck the bottom out of there tanks in less than half the NDL bottom time. it very much has a place but most dont use it there, it's just an ego thing for them, an expensive ego thing.

Exactly. If you can't take advantage of the extended bottom time because of air consumption, it's just costing you money for nothing. I do use Nitrox where it's available.

 

[dumpsterDiver]

I dive nitrox to the NDL limit and past it for repetative dives often. The increase in bottom time for repetative dives is huge. One day my nitrox computer broke and I had to go to an air computer. I did 3 or 4 dives on nitrox and on the last dive had a 36 minute deco on the air computer, I did only 10 minutes because I pretty much knew the nitrox profiles and what should work.

I almost never violate a computer, but nitrox allows a lot more diving. I have big tanks and make good use of the extra time that nitrox provides.

Also, with regard to the data that indicates that nitrox divers have a similar bends rate as air divers : I suspect that their are many divers that follow their nitrox computer and do alot more diving each day then they could on air.. I wonder if the data could be interpreted to mean that nitrox has been shown to allow people to dive a lot longer than on air and still have no increase in bends, This indicates to me that the stuff WORKS, rather than indicate it has no measurable benefit.

 

[fisherdvm]

I'm 100% in agreement until the last sentence.

If it is a low stress dive -- far from NDL; or if to NDL or beyond, then decompressed properly with a proper ascent profile -- neither A nor B will have post-dive fatigue, so therefore nitrox will have no effect. IIRC, the DAN study that concluded "no effect on post dive fatigue" didn't push the limits. If there isn't any signficant DCS-induced fatigue, then there isn't going to be any difference.

I am not sure if we can write this theory off, based on the study, quoted by DAN, but not endorsed by DAN.

One study, on fireman, at atmospheric pressure, showed less fatigue when breathing nitrox.

One study, done on miners, breathing compressed nitrox air at exposed to gas at higher than 1 ATM, showed less fatigue with nitrox.

There is more going on here than just DCS induced fatigue. We will just have to wait for more studies to be done.

 

[Diver Dennis]

Just a thought. Would breathing deeply and slowly allow your lungs to absorb more of the oxygen in Nitrox or is the amount of extra O2 too small to make a difference?

 

[fisherdvm]

Just a thought. Would breathing deeply and slowly allow your lungs to absorb more of the oxygen in Nitrox or is the amount of extra O2 too small to make a difference?

I wonder if this would decrease the dead space ventilation and allow more efficient exchange of air. Dead space ventilation would waste more oxygen, as you are rebreathing "used" air low in oxygen, high in carbon dioxide...

You might have a point Dennis.