First Time Nitrox

[tursiops]

@Francesea that rumour has evolved from people diving nitrox as if they were on air so they have less nitrogen loading. If you dive nitrox to the NDL's then if you feel different it's a placebo since you have the same theoretical nitrogen loading in your tissues

It is a myth that it is a rumor, and there are perfectly good physiological reasons to feel better after a Nitrox dive....but not everyone may be sensitive to the differences. The key to understanding the positive effect is that you are attempting to offgas during your ascent phase, even on a gradual, multilevel ascent. That offgassing is MORE efficient if you are breathing Nitrox, because each breath has less Nitrogen in it than it would have if it were air, so the offgassing gradient is more favorable. The tables do not take this into account; they assume the only effect of Nitrox is less on-gassing compared to air. The off-gassing advantages of Nitrox are just not part of the calculations. It is a small effect, most apparent after a series of dive, especially deeper, longer ones, and manifests itself as keeping you farther away from "subclinical DCS," a.k.a. a feeling of tiredness after a dive. I can provide no citations to this explanation, but I am confident they will appear in time. There are just too many people experiencing the effect for it to be ignored.

 

[MaxBottomtime]

The plural of anecdote is not data.

 

[boulderjohn]

If you'd paid attention during your nitrox class, you wouldn't have needed to ask that question.

Spoiler

You always round up

Storker was incorrect in this. PADI has always taught to round to the nearest while digit, which is rounding up in some cases and rounding down in some others.

The reality is that it doesn't really matter all that much. A half percent one way or the other is not going to make enough difference in MOD, EAD, or anything else to have any real impact on your safety. Things are just not cut that fine.

 

[tbone1004]

@tursiops if you are diving computers, they are tracking all of that and let you out of the water with the same tissue loading and have the offgassing gradients factored into the algorithms, not just the ongassing. If you dive computers to NDL's you're going to have the same effects if pushing to the NDL's. If you dive tables based on EAD calculations, then yes, but variables have changed at that point. I have seen nothing but anecdotal evidence on the claims of nitrox being better for you if dove to the same limits as air

 

[tursiops]

I have seen nothing but anecdotal evidence on the claims of nitrox being better for you if dove to the same limits as air

Nor have I. But the logic error you are making is that YOU feel no positive effects, therefore NOBODY does. Doesn't it strike you as curious that many folks relate the same anecdote? Even when they told it is just a placebo?

 

[tbone1004]

Nor have I. But the logic error you are making is that YOU feel no positive effects, therefore NOBODY does. Doesn't it strike you as curious that many folks relate the same anecdote? Even when they told it is just a placebo?

the algorithms track tissue ongassing and offgassing rates as a function of the gas mixes they are told you are diving. Those may or may not be right, but that's the algorithms. If you dive to NDL, it is assuming direct ascent which lets you leave the water with the same theoretical tissue loading whether you are diving air, or trimix, or anything in between. With the same theoretical exit tissue loading, it is not plausible that you would feel better when diving on nitrox.
What normally happens is people are gas limited not NDL limited, especially on nitrox, and because of that they are coming up with a lot less nitrogen loading. That would explain feeling better at the end of the dive, but it's because they dove the equivalent of a shallower dive for a shorter amount of dive and thus had less nitrogen in their tissues, not because nitrox is a wonder drug.

I feel better coming out of the water with a GF high of 70 vs a GF high of 80, whether I'm diving air or nitrox, and whether it's an NDL dive, deco with backgas only, or O2 deco. The key is nitrogen when you exit the water, not what you're breathing

 

[ToyZuki9615]

I took the non-computer Nitrox class through PADI in 2014 (I think). We were taught to round to safety, up for MOD, down for NDL.

 

[Steve_C]

Doesn't it strike you as curious that many folks relate the same anecdote? Even when they told it is just a placebo?

When I was in grade school I got worried about getting a sick appendix and began to experience frequent stomach/intestinal pain. My dad took me to the family doctor who I knew well, his son was my best friend. Doctor listened to my complaints and then the doctor went to his cabinet and brought me back a while pill and said take this. I looked at it and smart ass that I was said "Thank you for the placebo". Took the pill and I did not have the stomach pain ever again.

Much of how we perform and feel is all a state of mind anyway.

 

[topher10]

I thought I read somewhere that air is not the ideal gas to dive at any depth, although it is the cheapest gas to dive at all depths.

 

[Steve_C]

I thought I read somewhere that air is not the ideal gas to dive at any depth, although it is the cheapest gas to dive at all depths.

Cute but not true at depth < 10 ft or depth >300 ft, well depth > 300 ft works it you ignore all the funeral expenses.