Nitrox extends NDL but does it have other benefits?

[CamG]

Great thread Archie and rhwestfall / Wookie awesome posts!
I have heard unofficial quotes from Dive Op's about the reductions in DCS with Nitrox use but again there are nothing official out there.
Nitrox is a tool that when used correctly benefits the user.
How it does can be factual or not but as much as we know about physiology we still just do not know!
Computers track our on gas and off gas but as rhwestfall mentioned a proper ascent will help to battle micro bubbles from growing into a problem.
Good old fashion skill mastery and conservatism should be employed on every dive!

If available use Nitrox, I do and love it!
Just observe and keep skills sharp mastery doesn't end after you get your card.

CamG

 

[Wookie]

I wonder.....what was your rate of divers wearing computers from 98-06 compared to 06-now. I wonder if that was a more direct causal link.

That's a good question, and I don't know the answer. What I do know the answer to is that no diver diving tables (we don't insist on a computer, but if you don't, you must follow tables, and we check) has ever reported symptoms of DCS on the Spree. Only divers on computers have ever been treated for DCS. Since I've been here.

 

[Nirvana]

What mixes do you usually dive Nirvana that has MORE AIR than NITROGEN?

I assume you are referencing the "mixture that contains less nitrogen than air" part of my post. I meant to say a mixture whose nitroge content is lesser than that of air, that is, less than approximately 78% nitrogen.

And yes, I know there are other types of mixture with potentially lesser nitrogen content (trimix, heliox, hydrox etc), but I didn't think it was relevant to the question asked.

In any event, perhaps I should have phrased that sentence better.

 

[Redshift]

Here is some anecdotal evidence for you about DCS. I've been running a liveaboard since 1998. Same liveaboard. During that time, we see about 500 customers per year, who complete in average 7500 dives. From 1998 to 2006, we charged an extra $10 per day for nitrox, some used it, some didn't. In 2006 we raised the price for the dive trip to include nitrox, so most everyone used it. From 1998 to 2006 I saw 4-8 cases of DCS per year, which meant we had to bring the trip home early. Since 2006 we've seen zero cases of the DCS, and one case of Immersion Pulmonary Edema, and suspect a second case, but both of those divers were on rebreathers.

Were the DCS cases from divers on air?
I wonder also if the fact that people use nitrox prevents them from going as deep as they'd go on air and that also contributed to safety...

What mixes do you usually dive Nirvana that has MORE AIR than NITROGEN?

That question makes no sense. Nirvana said that nitrox has less nitrogen than air (has) (because it has been replaced by oxygen) and went from there to the extended NDL...

 

[gekodivebali]

At a personal level, I also feel that deco'ing on pure O2 helps with post dive fatigue. I'm not sure about other dives since I tend to extend my bottom times. The guides/instructors at our operation dive Nitrox since they get it at no additional costs. Not sure they get less tired though.

 

[Wookie]

Were the DCS cases from divers on air?
I wonder also if the fact that people use nitrox prevents them from going as deep as they'd go on air and that also contributed to safety...

It was implied, but I should have specified. Yes, all DCS cases but one were on air. The one on Nitrox was a clear case of a yoyo safety stop, from 25 feet to 10 feet. multiple times.

Our diving is for the most part limited by the topography. We tend to dive flat bottom in 80-100 feet of water patch reef, although some of the patches are significant. On an oil rig it is possible to get as deep as 400 feet, but we limit divers from doing that. We also have a wreck that is 157 to the sand, but we limit that too. In any case, we limit all divers by procedure to 130 feet, and sit them out if they bust the depth limit.

 

[scubadada]

1. Nitrox has no effect on SAC in anyone I know, nor myself.
2. There is no PROOF of less fatigue or other benefits of nitrox over air. Some people claim to feel a difference, but theres no evidence to support it. There is however a theory involving subclinical DCS

Correct/correct. I stay down longer on nitrox, push NDL limits just as much as I would on air. I would not expect to and do not feel different on nitrox as compared air. If someone subjectively feels better diving nitrox, good for them.

---------- Post added April 14th, 2014 at 08:59 AM ----------

Here is some anecdotal evidence for you about DCS. I've been running a liveaboard since 1998. Same liveaboard. During that time, we see about 500 customers per year, who complete in average 7500 dives. From 1998 to 2006, we charged an extra $10 per day for nitrox, some used it, some didn't. In 2006 we raised the price for the dive trip to include nitrox, so most everyone used it. From 1998 to 2006 I saw 4-8 cases of DCS per year, which meant we had to bring the trip home early. Since 2006 we've seen zero cases of the DCS, and one case of Immersion Pulmonary Edema, and suspect a second case, but both of those divers were on rebreathers.

Same dives but longer on nitrox? If the dives are the same duration, perhaps gas rather than NDL limited, I could understand your observation.

 

[Redshift]

If some people feel better and less tired with nitrox isn't that proof that nitrox helps some people feeling less tired?
Just because some people don't notice it, that doesn't disprove that others notice an effect.

 

[Wookie]

Same dives but longer on nitrox? If the dives are the same duration, perhaps gas rather than NDL limited, I could understand your observation.

I know that about 80 feet for me is the tipping point where I become gas limited on a steel 100 instead of NDL limited, and I assume it's about the same place for most divers. I'm a big guy with a 12 liter lung volume, so I may be a bit of a huffer. Deeper than 80 feet, I go out on NDL, shallower than 80 feet, I go out on gas volume. Since most of our diving is done in the 80 foot or shallower range, I would say that most divers are not limited by their NDLs (except later in the week), but by gas volume. What they are really limited by on longer trips is ridiculous dive computers that use an oxygen timer instead of an algorithm, although I guess you could say a timer is an algorithm. I believe it is impossible to exceed your oxygen clock on 32% doing 5 dives per day of any recreational duration or depth. But by the end of the week, those with recreational style computers are definitely O2 limited, while those on real dive computers (sorry, insert sneer here) are barely on the O2 clock.

I only dive 32% or trimix, as applicable, even if I have to pay for it at other ops. Air is for tires.

 

[MXGratefulDiver]

Locally I use EAN32 for almost every recreational dive I do. It allows me to do a lot of the profiles I prefer to do without the need to bring a deco bottle. Sometimes my dive computer registers that I'm in deco, but usually it clears before I reach 20 fsw. In those cases I tend to hang around in the 15-20 fsw range a few extra minutes anyway.

I tend to feel less tired after diving nitrox rather than air. People tell me it's all in my head. That's OK, if my head makes my body feel better then it's working for me ...

... Bob (Grateful Diver)