Enhanced air...does it help fatigue?

[Capt Jim Wyatt]

There is no empirical evidence to support this, only anecdotal.

 

[Hawkwood]

I rarely use enriched air diving locally. Cool water, altitude, dry suit, lots of weight (relatively), long walks in gear to the entry or a long surface swim...I'm pretty darn tired after a couple of dives.

I usually use enriched air when diving on trips and I'm doing lots per day over a period of time. Warm water, light exposure suit (or skin suit), not much weight, flop off the side of a boat...I'm still pretty perky after a day of diving.

Must be enriched air...it's the only variable, right?

When I teach enriched air and ask my students at the beginning of the class why they want to use enriched air, I invariably get one giving that as the reason. I give them the above story.

I agree with Rick - YMMV.

The question was asked in Basic after all, by a new diver with 12 dives. Let's put it in context.

 

[boulderjohn]

You often hear it said that when using nitrox, you either get more safety (by diving nitrox to air limits) or more bottom time (by diving nitrox to nitrox limits). You can't get safety and more bottom time. A recent article in Dive Training magazine stated exactly that. It's safety or extended bottom time--take your pick.

I find that curious.

Let's say I am planning a dive to 70 feet. If I am diving on air, according to the PADI RDP my maximum NDL is 40 minutes. Let's say that I instead use 36% nitrox. In that case, my NDL is 75 minutes--considerably more.

So what if I dive for 50 minutes? That is nowhere near the NDL for nitrox 36, and it certainly looks to me to be an extended bottom time.

 

[tursiops]

There is no empirical evidence to support this, only anecdotal.

Also, there is no empirical evidence to deny this, only anecdotal.

Jim, it sounds like you just entered the thread. Read post 54, especially.

---------- Post added December 14th, 2015 at 01:32 PM ----------

You often hear it said that when using nitrox, you either get more safety (by diving nitrox to air limits) or more bottom time (by diving nitrox to nitrox limits). You can't get safety and more bottom time. A recent article in Dive Training magazine stated exactly that. It's safety or extended bottom time--take your pick.

I find that curious.

Let's say I am planning a dive to 70 feet. If I am diving on air, according to the PADI RDP my maximum NDL is 40 minutes. Let's say that I instead use 36% nitrox. In that case, my NDL is 75 minutes--considerably more.

So what if I dive for 50 minutes? That is nowhere near the NDL for nitrox 36, and it certainly looks to me to be an extended bottom time.

Exactly!
But it is so much easier to argue black-and-white, sticking with the extremes.

 

[boulderjohn]

Let's take two divers doing the same 2-tank dive trip in the Pompano Beach area, a place I dive frequently. The trip consists of a wreck dive to 80 feet followed by a reef dive to 50 feet. Both divers are using the same sized tanks typical of recreational divers, and both are diving PADI tables. One is diving air, and the other is diving nitrox 36.

The air diver begins the ascent on the first dive at 30 minutes, as required by the tables. Assuming the diver has a decent breathing rate, the diver will finish the dive with about 1,000 PSI and will be in the R pressure group. After a 58 minute surface interval, that diver is back in the water for the 55 foot dive. That puts the diver into the G pressure group. The dive operator limits that dive to one hour for scheduling reasons. The diver leaves the bottom at 50 minutes, 4 minutes short of the NDL, which brings him or her to the surface in the X pressure group, at the very edge of the No Decompression Limits.

The nitrox 36 diver extends the first dive to 40 minutes, a 33% extension of bottom time, arriving on the surface with a comfortable gas reserve and in the O pressure group. Having stayed down longer while the air diver is pitching about on the boat, the diver gets a shorter surface interval--48 minutes--before the next dive. The diver gets in the water in the F pressure group as a result. That diver, too, leaves the bottom at 50 minutes, 73 minutes away from the NDL, which brings him or her to the surface in the R pressure group, nowhere near the very edge of the No Decompression Limits.

Summary: The nitrox diver got a 33% extended dive for the first dive and spent 10 minutes less sitting around on the boat waiting for the second dive. Despite the shorter surface interval, and most importantly for this discussion, the ntrox diver ended the dive day far, far from NDLs, while the air diver was right at the very edge of the NDLs. I have to think that has an impact on decompression stress. That comparison is for a 2-tank dive. Imagine how that would carry over for a week of 4 dives per day on a liveaboard.

 

[Hawkwood]

---

---

A ScubaBoard Staff Message...

Hey folks, this has been an interesting Thread to say the least. Very informative and even a bit of humour. When formulating your replies, try to remember what Forum this in and the context in which the Thread was started. The Forum is certainly appropriate for the question as posed by the OP.

---

 

[SouthSideScubaSteve]

I think I need to quit my job and head south to do research on this topic... anyone know how to get a research grant ??


Also, is there a way to Like an entire thread??

 

[DevonDiver]

11 years ago... http://www.scubaboard.com/forums/ask-dr-decompression/67732-nitrox-reduces-fatigue.html

People saying the same,... myths and denials still exist...

This would be a good one for the "Ask Dr. Decompression" forum.

The reason that nitrox reduces fatigue is because it reduces "decompression stress", or subclinical symptoms of DCI.
There are a whole host of things that happen in our bodies when we are offgassing, and one of them is an immune response to the microbubbles. Of course, an immune response in the blood results in the lymphatic system having to carry off the excess dead white cells produced to mount the attack. The immune response itself, as well as the lymphatic aftermath, both serve to create fatigue, stiffness, perhaps sore muscles, etc...

Remember... we're talking subclinical DCS. Just as "every dive is a decompression dive", you could also say that after every dive we are all a "little bit bent". Back in OW-101, wasn't fatigue taught to us as being one of the signs of DCS?
It is generally the second symptom... right after denial.

Nitrox can help to reduce this.

Until you take advantage of the extended bottom times available from nitrox... then you're back to square 1 with a full nitrogen load.

Similar benefits to nitrox have been reported by divers adding deep stops to their profiles.

Hello Readers:

Nitrox vs. Air

The jury seems to be out on this. I suspect it is, as pointed out by one responder, related to the profile and its stress. The Undersea and Hyperbaric Medicine article quoted above did not have a very stressful profile. [I pointed that out as one reviewer of this paper.] These dives would not make a very definitive test of the hypothesis. :06:

Most people seem to implicate the growth of microbubbles, and the prevention of this by reducing the nitrogen in the breathing mix. It is curious that slowing ascents and deep stops produce the same, or similar effects.

Dr Deco :doctor:

Readers, please note the next class in Decompression Physiology :1book:
Page Not Found > USC Dana and David Dornsife College of Letters, Arts and Sciences
Michael R. Powell, M.S., Ph.D.

 

[kelemvor]

I know, this horse is already dead...

I think nitrox helps me with fatigue. Maybe it's placebo, maybe it's subclinicial dcs from microbubbles, maybe it's the reduced dandruff... In the end, I don't really care.

I think it's worth the $5 extra per tank it usually costs me.

It's a shame it's still treated as "voodoo gas" with agencies selling nitrox classes separate from open water... well, if you don't invade foreign countries with Elena, anyway...

 

[Kairoos]

At my LDS a nitrox fill is $6 and an air fill is $4, regardless of tank size. I think I remember feeling better switching from air to nitrox, but I haven't dove air in probably 40 dives now. I don't see a reason to use air, especially if you are able to get the mixes that you want.