air vs nitrox

[cummings66]

Well, there's facts and then there's facts.

I've always said and you're probably seen in other posts where I claim the mind is a powerful thing allowing us to do remarkable things. I fully believe that if a person is convinced that they will feel better diving Nitrox then they most certainly will feel better. It's like those amazing feats of physical strength somebody has when they lift a car off their loved ones, etc. The human being is certainly a complex creature that controls to a large extent their own reality by their mind.

That said, not one diver at my LDS can say they ever felt better diving Nitrox, and the instructor for the course does not make any claims you'll feel better.

 

[dilligaf368]

I usally get very tired after working 6-10hrs underwater on Air. but then again I'm usally tired after working a 10hr day anyway! B--------

 

[Diver Dennis]

I feel the same on Nitrox or air. I just got back from the Philippines and was doing 3 or 4 dives a day and did the Nitrox challenge to see for myself. I do believe it is better for your body to dive an enriched mix. I did find that a chocolate donut before diving did make me feel better though...

 

[Rick Murchison]

the mind is a powerful thing ... if a person is convinced that they will feel better diving Nitrox then they most certainly will feel better

And that, I think, is the bottom line
Rick

 

[Thalassamania]

I stand corrected: Might feel better.

But really, I started using NITROX back when it was devil-gas and rather than pushing it the LDS vilified it. At that stage many tropical destinations (e.g., Grand Cayman) had banned its use.

As I observed in a paper published back in '92: "Is 25-FSW less narcosis on a 110-FSW dive worth the trouble of obtaining EAN-36 and the safety concerns of its manufacture? Probably not. However, the increased no-decompression dive time might be. A no-decompression 110-FSW air dive is limited to 20 minutes, but with EAN-36 the limit is increased to 30 minutes. That is half again as much bottom time and significantly greater proportional gains are available at shallower depths!"

The Royal Adelaide Hospital Study that Tom Neuman reviews notes that, “Compression took 8-10 minutes and following the 40 minute bottom time the subjects were then decompressed in a linear fashion over 15 minutes.”

Tom clearly points out the major flaw in the Royal Adelaide Hospital Study: "One might easily argue that such a dive does not entail a major degree of “decompression stress” and therefore it is not a fair test of “nitrox” versus air since the stress of the dive was so low that one would not “expect” fatigue regardless of the breathing gas."

He goes on to state: "The authors feeling regarding this point is that the experimental dive profile closely approximates the kinds of dives that recreational divers perform and therefore the kinds of dives that are felt to produce less fatigue when one uses “nitrox”."

So it is quite possible that folks who are diving conservative, staying way back of the no-D limits and making very prudent ascents are not feeling the “extra” energy of NITROX because in is not so much a question of “extra” energy as preventing damage when one goes a little closer to the line.

Our dives where pretty much square profile: moderately rapid descent to the 110 ft. study site; time on bottom to almost the no-D limit; an ascent to 20 fsw and then 10 fsw for 3 minute safety stops. This would account for our observations that with NITROX we "felt better" (a great technical term, no?).

 

[rockjock3]

Got a cite for this.

Ummmm, your BOW book. Even it explains that breathing compressed air at depth, due to it being denser, is harder for you body.

 

[rockjock3]

Not sure there is extra effort in breathing per se. The supply of a SCUBA system delivers about the same volume of gas as on the surface and does this while adjusting to the depth.......

Second, with enriched air (more oxygen), the body gets more molecules of O2 per breath, hence the body when using the same effort to extract O2, gets more molecules/effort.........?

Yes, your body is is recieving the air at an increased pressure so that you can fill your lungs. The problem is however that the gas is more dense as you get deeper. This makes the oxygen more difficult to extract for the lungs, not necessarily easier just because there is more oxygen in the volume.

 

[JeffG]

Ummmm, your BOW book. Even it explains that breathing compressed air at depth, due to it being denser, is harder for you body.

Thats only answers 1/2 of what you said. And quite frankly, the "effort" in breathing compressed air isn't going to make anyone feel tired. Its harder...but not that much harder. Its not like you are running a marathon.

What tires you out is the extra effort required by your body to breath in and out as well as extract oxygen from the air.

Extracting oxygen from air in the lungs doesn't take any effort at all.

 

[JeffG]

This makes the oxygen more difficult to extract for the lungs, not necessarily easier just because there is more oxygen in the volume.

BS

 

[rockjock3]

Well, there's facts and then there's facts.

I've always said and you're probably seen in other posts where I claim the mind is a powerful thing allowing us to do remarkable things. I fully believe that if a person is convinced that they will feel better diving Nitrox then they most certainly will feel better. It's like those amazing feats of physical strength somebody has when they lift a car off their loved ones, etc. The human being is certainly a complex creature that controls to a large extent their own reality by their mind.

That said, not one diver at my LDS can say they ever felt better diving Nitrox, and the instructor for the course does not make any claims you'll feel better.

Yes, the mind is a powerful tool, I would venture to say the most powerful. The mind isn't responsible for being able to lift a car off a loved one though. The culprit for that would be adrenaline surging through the body actually giving you the strength, not the mind telling you that you can lift it.