Nitrox instead of air for lower DCS risk?

[Averill]

First post here on scubaboard.. Been enjoying reading everyone's comments for a while now, thought I might try and add something for a change. :confused4

Diving nitrox should decrease the chance for DCI. If EANx** increases your no-decompression bottom time, it seems like a logical assumption. (To me anyway.)

However, while taking a PADI Nitrox course not too long ago, I was told that there really isn't a meaningful safety improvement. (p.16-17 in the PADI Enriched Air Diver Manual Version 2.1) The manual is dated 2004, so there may very well be new material out. Do other agencies say the same thing? For legal purposes?

Seems a little odd, just thought it might be worth mentioning.

 

[gangrel441]

I don't have the manual in front of me right now, but IIRC, what it states is that diving EANx** well within the air NDL does not provide a measurable safety margin over diving air well within the NDL. It may not be expressly stated, but diving EANx** right on the air NDL does provide a measurable safety margin over diving air right on the air NDL. Also, diving EANx** right on the NDL for the mix you are using provides no safety margin over diving air right on the air NDL, but EANx** provdes more bottom time at the same depth.

 

[Johnoly]

Just because there's a lot of newbies that read these threads, to clarify I think this thread is discussing different gases and their effects ONLY. DCS has many other determining factors, like ascent rates and especially hydration among other factors that can bring on DCS. Just for our newer divers, Using Nitrox does not prevent DCS !!. There are some excellent discussions above here.

 

[DandyDon]

Diving Nitrox to lower DCS risks in most folks is like lowering the top speed in the US to 55 mph - it has some benefit, altho I don't want to return to 55 mph.

BigTuna didn't say how old he is, but he did say...

I want to minimize age-induced risks of DCS.

Sure, dive Nitrox, stay well above the MOD and keep your computer well into the green. With the MOD avoided, it couldn't hurt. Dive 36% on the shallower dives.

I'm 58 and I dive Nitrox on many dives that I could do on air.

 

[RiverRat]

PADI's standard line is that it does not reduce the risk of DCS, but I think that's just one big CYA exercise on their part. If they say nitrox has a lower risk, then they're also saying air has a higher risk.

___

Keep in mind they're talking about DCS, which means Decompression "Sickness", meaning getting bent, AGE etc.

In that case breathing Nitrox won't reduce a chance of "decompression sickness" and everything it includes.

If diving Nitrox on Air tables, then it will surely reduce your nitrogen load giving you a better safety margin. And even if diving with other divers on air, and not using the air tables you'll still have a safety factor if you all dive the same profile.

 

[Kim]

If I were to adopt EANx32 as my standard mix, my normal depths would be comfortably below its MOD.

I presume you mean 'above' or 'within'? As for Nitrox.....well I'm 54 years old and I figure they don't call it 'geezer gas' for nothing! eyebrow Unfortunately I can't get it easily where I live in Japan but I use it exclusively if I'm on a liveaboard in Thailand or something like that. It's safer IMO.

 

[BigJetDriver]

Who is this "we" Andy?

I do not IN FACT know whether I am diving "safer" on EANx than that of air, I dove a gazillion dives on air to depths below 100' over twenty years - I'm still here.

Now, as I've said, I stopped diving on air seven years ago completely (after Trimix 2)... so...

Dan,

This "we" is people like myself, and many others who teach instructors how to teach this stuff.

Certain things about Nitrox rise to the level of facts. First, we are merely changing the ratio of Mother Nature's Nitrox (i.e. air). Thanks to Dr. Morgan Wells and Dick Rutkowski of NOAA, two mixes of Nitrox were standardized, and named NOAA NITROX I and II (NNI and NNII). These are, respectively, 32% and 36% oxygen, with 68% and 64% nitrogen.

Logic demands that, if we dive air to a given depth for a given time, we take on a certain amount of nitrogen in solution (us) based on the physics of the problem (i.e. Henry's Law). If we then dive NNI or NNII to the same depth for the same time, we take on less nitrogen. Things are simple, up to this point.

Then we get to the problems of levels of increased oxygen, and also to statistics. Suffice it to say that standarization has determined that, for reasons of safety, we do not wish to go above a partial pressure of 1.6 for O2. That limits our depth to 110 fsw for NNII and 130 fsw for NNI (don't begin the hair-splitting yet). Air, of course, does not reach that point until 218 fsw.

Conveniently, the depth limits just named for our Nitrox mixes are right within the recreational diving limits. Simple, yes? Simple, no!!:06:

We have to decide which we want; an increased margin of safety, or the same safety margins (as on air), but with more bottom time. Statistically, there is only a minor increase in the safety margin when diving nitrox on air tables. It is there, but it is minor. Most folks opt for the "more bottom time" option.

There are, of course, lots of anecdotal reports from the field, that diving on Nitrox mixes just makes one feel better at the end of a diving day, compared to air diving. Now, I had one famous researcher, whose name you would know well were it mentioned, who told me that anecdotal reports are not regarded highly by researchers. One, because they come from un-trained observers, but mostly because, two, the researcher doesn't get to have his name on the study and doesn't get paid for it!

So, while this is the quick and dirty, it really does boil down to personal choice as to the way you, as a diver, utilize Nitrox. The "Voodoo Gas" has really come into its own!:luxhello:

 

[rawls]

I'm an old toad, but in good shape. I want to minimize age-induced ri
risks of DCS.

DAN did alot of research on age in terms of increased risk of dive related illnesses. It has been a long time since I read it, but I believe the jist of the research showed there was no significant differences, assuming an older diver is in "good" shape, between the older and younger diver. If my memories of the research are basically correct then the Nitrox vs Air question wouldn't be an issue really. If I'm wrong about it...never mind...I'm one of those older divers...Could be just wishful thinking

 

[BigTuna]

Sure, dive Nitrox, stay well above the MOD and keep your computer well into the green. With the MOD avoided, it couldn't hurt. Dive 36% on the shallower dives.

I'm 58 and I dive Nitrox on many dives that I could do on air.

Thanks for the help, young fella (I'm 64) and everybody else. I think that sums up the concensus pretty well, if I add keeping the computer on an air setting. It can't hurt and might help some. In addition I run the computer (Cobra) at one level of conservatism. Overkill? I don't want to find out--I'm having too much fun.

Incidentally, if this practice only helps "some" in holding DCS at bay, I imagine that's because the percent of nitrogen in EANx is only around 15% less than in air. That's an improvement, but it's not stellar.

If/when I find my gas consumption gets low enough that I'm running up against the no-deco limit, that would be a happy day. I suppose then I'd consider using a nitrox setting and using the extended bottom time. Dunno. Not totay's problem.

 

[Walter]

Keep in mind they're talking about DCS, which means Decompression "Sickness", meaning getting bent, AGE etc.

Nope. You're thinking of DCI - Decompression Illness. DCS - Dcompression Sickness is just the bends. DCI includes DCS as well as AGE and the other lung over expansion maladies. DCI is a confusing term and I see no need to ever use it. Now, it's even confusing people as to the meaning of DCS.