Benefit of Nitrox?

[Divetech99]

Thanks. Agree with you. Just don't know why the myths of lower air consumption and less fatigue continues to permeate. Placebo effect probably.

 

[NateS]

When nitrox is used as if it were air (meaning you stay down the same amount of time you would on air), it is safer. You absorb less nitrogen, have less chance of DCS, and you may feel better afterward as a result, especially if diving multiple times. When using nitrox you can't go as deep as when using air because nitrox has more oxygen and you would absorb too much oxygen.

When nitrox is used to stay down longer then when using air, it is NOT safer but instead provides the same risk as when using air. You absorb the same amount of nitrogen and have the same chance of DCS as you would using air, except you get to stay down longer.

Gas consumption is the same on both gases. If your dives end because you run out of gas, nitrox won't let you stay down longer (but you will absorb less nitrogen). If your dives end because you have absorbed as much nitrogen as is safe, then nitrox will let you dive for longer.

 

[DogDiver]

I haven't breathed compressed air since 1998. Dive nitrox in the caves, wrecks, Florida keys, Roatan. Get the idea? Less nitrogen is always better. [emoji41]
Oh and as a plus, in north Florida banked nitrox sold by the cubic foot is cheeper than fixed rate air fills.

Sent from my iPhone using Tapatalk

 

[scubadada]

DAN says "no"

Alert Diver | Air, Nitrox and Fatigue

"Despite a common impression that diving on nitrox may cause less fatigue than performing the same dive using an air mixture, scientific research to date has not found solid evidence to support such an assumption."



This article says "no"

Harris RJ, Doolette DJ, Wilkinson DC, Williams DJ (2003). "Measurement of fatigue following 18 msw dry chamber dives breathing air or enriched air nitrox".Undersea and Hyperbaric Medicine (Undersea and Hyperbaric Medical Society) 30 (4): 285–91. Measurement of fatigue following 18 msw dry chamber dives breathing air or enriched air nitrox.

"Diving to 18m while breathing air produced no measurable difference in fatigue, attention levels, ability to concentrate or DHS scores, compared with breathing EANx 36%."




This article says "no"

Chapman SD, Plato PA. "Measurement of Fatigue following 18 msw Open Water Dives Breathing Air or EAN36.". In: Brueggeman P, Pollock NW, eds. Diving for Science 2008. Proceedings of the American Academy of Underwater Sciences 27th Symposium. http://archive.rubicon-foundation.org/xmlui/handle/123456789/8005

"Results from this study did not support the contention that using EAN36 as a breathing gas reduces post-dive fatigue. To date, research has indicated that there is no difference in fatigue levels between air and EAN36 dives."

Since when have people let a little science get in the way of their beliefs?

 

[NateS]

It may not reduce fatigue, but it definitely reduces nitrogen uptake. What ramifications does that have? It seems reasonable that people "feel better" after using nitrox, even if they just as fatigued as they would be using air.

 

[MaxBottomtime]

The rate of DCS is less than .01% using air. Using Nitrox lowers that risk. It isn't much lower but if it makes divers believe they're safer they use it. I prefer to use it for accelerated deco gas only.

 

[NateS]

What does the 0.01% chance mean? DCS can be anything from unexplained fatigue, itching, joint pain, dizziness to hearing loss, paralysis, embolism, and more.

 

[Storker]

The rate of DCS is less than .01% using air. Using Nitrox lowers that risk. It isn't much lower but if it makes divers believe they're safer they use it. I prefer to use it for accelerated deco gas only.

It may of course be pure, unadulterated placebo, but I've found that diving less aggressive profiles reduces post-dive fatigue. Proper multi-level profiles instead of square profiles, a good safety stop, ascending on a (dSMB) line instead of just corking from the SS or using nitrox, particularly on deep or repeated dives, all seem to reduce my post-dive fatigue. Since post-dive bubbles have been shown to be prolific even in DCS-asymptomatic divers, I'm pretty convinced that nitrogen loading induces a stress on the body, even if you don't exhibit DCS symptoms.

WRT the studies, did they use the correct methodology? A fit 20-something doing a single chamber dive to 18m doesn't necessarily react the same way as a slightly chubby middle-aged guy doing two or three dives to 25-30m in one day.

Anyway, if it works for me, I'm happy. Even if it's placebo...

 

[Bob DBF]

Thanks. Agree with you. Just don't know why the myths of lower air consumption and less fatigue continues to permeate. Placebo effect probably.

Read the studies.

The first was one tank in a chamber, exercising not diving.

The second was only two tanks, but at least it was diving. They did find a difference between air and nitrox. The problem, I see, is they were only measuring fatigue which they see as different than the side effects of offgassing of N2 which they were not measuring. What they found was on the fatigue test there was no difference but the on another test the divers felt better on Nitrox. The lesson I see is that you will get just as fatigued, but feel better.

Measurement of Fatigue following 18 msw Open Water Dives Breathing
Air or EAN36
Scott D. Chapman, Peggy A. Plato
Department of Kinesiology, San Jose State University, One Washington Square, San Jose, CA 95192,
USA
scott_chapman@wvm.edu
plato@kin.sjsu.edu
Discussion(my excerpt from)
The purpose of this study was to compare fatigue levels between two test sessions consisting of two
repetitive dives breathing either air or EAN36 in an open water environment. It was hypothesized that
the reduced nitrogen level and subsequent higher oxygen levels would lead to decreased fatigue
Rubicon Research Repository
9
following two repetitive EAN36 dives. Analyses of reported fatigue failed to support this premise;
however, scores on the Diver Health Survey did exhibit a significant decrease following dives using
EAN36 compared to air.

Reduction of fatigue or less stress from offgassing, for me, I don't care which is making me feel better. Also I see no difference over one or two dives so for that I dive air, it makes a difference on multi day multi dive trips, and on those I now dive Nitrox. So far there is no study on over 2 dives a day over multi day period, although the author of the second study thinks it might be worth a study.

Measurement of Fatigue following 18 msw Open Water Dives Breathing
Air or EAN36
Scott D. Chapman, Peggy A. Plato
Department of Kinesiology, San Jose State University, One Washington Square, San Jose, CA 95192,
USA
scott_chapman@wvm.edu
plato@kin.sjsu.edu
Abstract
SCUBA divers often report feeling fatigued upon conclusion of diving activities. Post-dive
fatigue is thought to be induced by increased energy demands of submersion in a hyperbaric
environment and decompression stress. Anecdotal reports indicate a reduction in post-dive
fatigue when using enriched-air nitrox (EAN). The purpose of this double-blind study was to
compare subjective fatigue levels experienced by SCUBA divers after two repetitive air dives
and two repetitive EAN36 dives on separate, nonconsecutive days. Eleven male participants
completed pre- and post-dive fatigue assessment using the Multidimensional Fatigue
Inventory and a Visual Analogue Scale, while general health was assessed using the Diver
Health Survey. Divers did tend to be more fatigued after diving; however, breathing gas
mixture exhibited no statistically significant effect. Participants did have significantly lower
Diver Health Survey scores upon the conclusion of EAN36 test sessions, possibly indicative
of reduced decompression stress.

The studies, so far, have focused on fatigue, not the overall effect on the diver. From what I gathered from both studies is that fatigue has a very specific meaning in the scientific community that is not the same or as broad as I would use. The last study said there was no difference in fatigue, but ran across the "feeling better" effect of Nitrox, since it was not being studying they could only comment about it.



Bob
-----------------------------------
“They are ill discoverers that think there is no land when they can see nothing but sea.”
― Francis Bacon

I may have been born at night, but it wasn't last night.

 

[RJP]

It seems reasonable that people "feel better" after using nitrox, even if they just as fatigued as they would be using air.

So, scientific evidence aside, it still "seems reasonable" to you?

:shocked2:

Here's what seems reasonable to me:

1. The typical recreational diver exhibits fairly lax skills and techniques; saw-tooth profiles, reverse-profile repetitive diving, relatively rapid ascents, short SI's, generally poor buoyancy skills, pushing NDLs, and has at best a rudimentary grasp of dive planning, tables, or their dive computers
2. Lax diving skills - while unlikely to put the typical recreational diver in a chamber - are likely to produce sub-clinical DCS or so called "silent bubbles" in the blood stream and body tissues
3. The silent bubbles from sub-clinical DCS that are experienced by typical recreational divers with lax dive skills are likely to produce symptoms of fatigue
4. Accordingly typical recreational divers with lax dive skills who dive nitrox will experience less bubbles, and therefor will experience less fatigue secondary to the sub-clinical DCS they ordinarily experience when diving on air

But seriously, let's be more objective and consider it this way...

• The data from well-controlled studies (eg all participants are placed in a chamber or otherwise subjected to exactly the same dive profiles relative to depth, time, ascent rate, etc which are controlled by the scientists conducting the study) show that divers using nitrox have no statistically significant difference in post-dive fatigue as compared to divers on air
• Anecdotal "data" from poorly-controlled studies (eg: typical recreational divers jump in the water, do their own thing, and tell everyone "I feel better") suggest that those who dive nitrox are less fatigued than when they dive air
• So it would appear reasonable to conclude from the literature that people who dive in a well-controlled fashion exhibit less fatigue than people who dive in a poorly-controlled fashion... irrespective of their choice of breathing gas.

---------- Post added September 6th, 2015 at 11:17 AM ----------

It may of course be pure, unadulterated placebo, but I've found that diving less aggressive profiles reduces post-dive fatigue. Proper multi-level profiles instead of square profiles, a good safety stop, ascending on a (dSMB) line instead of just corking from the SS or using nitrox, particularly on deep or repeated dives, all seem to reduce my post-dive fatigue. Since post-dive bubbles have been shown to be prolific even in DCS-asymptomatic divers, I'm pretty convinced that nitrogen loading induces a stress on the body, even if you don't exhibit DCS symptoms.

"What he said..."