Nitrox question for Dr. Deco

[WesTexDiver]

I think it's more simple than all of this. Breathing a higher concentration of oxygen can make you feel better even if you don't go diving. Why over simplify things.

 

[fisherdvm]

I think it's more simple than all of this. Breathing a higher concentration of oxygen can make you feel better even if you don't go diving. Why over simplify things.

I think what you meant to say is why over complicate things?

Your theory of breathing higher oxygen make you feel better might be correct, but the study done with nitrox using 11 divers would suggest that it isn't so.

Summary: Many divers report less fatigue following diving breathing oxygen rich N2-O2 mixtures compared with breathing air. In this double blinded, randomized controlled study 11 divers breathed either air or Enriched Air Nitrox 36% (oxygen 36%, nitrogen 64%) during an 18 msw (281 kPa(a)) dry chamber dive for a bottom time of 40 minutes. Two periods of exercise were performed during the dive. Divers were assessed before and after each dive using the Multidimensional Fatigue Inventory-20, a visual analogue scale, Digit Span Tests, Stroop Tests, and Divers Health Survey (DHS). Diving to 18m produced no measurable difference in fatigue, attention levels, ability to concentrate or DHS scores, following dives using either breathing gas.

As the divers were not pushed to the limit of their no decompression time, this might suggest that the benefit of nitrox was not reached. My guess is if you pushed these 11 divers closer to the no decompression limit with multiple or with longer deeper dives then the effect of nitrox on fatigue will be more noticed. The opinions of so called experts on why nitrox has helped with fatigue suggests either subclinical DCS is the culprit, or nitrogen narcosis as the cause of the fatigue. I would favor the subclinical DCS.

 

[Gene_Hobbs]

There was also an article, I think it was in Immersed, discussing the prospect that the cumulative impact of multi-day diving might have the effect of reducing complement system response on successive dives. The article suggested that the immune response just ran out of gas (my term).

There have been several studies that showed complement is not the best marker. In fact, I don't know anyone who was able to repeat the studies that did show complement activation with similar outcomes. The fact that they have not been repeatable brings major questions to the validity of those trials in my mind.

 

[Kendall Raine]

There have been several studies that showed complement is not the best marker. In fact, I don't know anyone who was able to repeat the studies that did show complement activation with similar outcomes. The fact that they have not been repeatable brings major questions to the validity of those trials in my mind.

Thank you, Gene.

Charlie has kindly agreed to send me a copy of the article. He thinks I got it backwards, anyway.

 

[Kendall Raine]

Do you know where you saw these first?

A dive shop owner told me about them. I couldn't find them around so I wrote Jane Pimlott at DDRC directly and she sent me copies.

 

[Charlie99]

Charlie has kindly agreed to send me a copy of the article. He thinks I got it backwards, anyway.

You have it right. I misread your comments.

The article comes to the conclusion that with repetitive multiday diving "complement system activation may acclimate you to resist DCS".

 

[miketsp]

Interesting, do you remember the citation here??

http://www.usfa.dhs.gov/downloads/pdf/tr_98bw.pdf

THE EFFECTS OF OXYGEN-ENRICHED AIR ON FIREFIGHTER JOB PERFORMANCE

 

[fisherdvm]

http://www.usfa.dhs.gov/downloads/pdf/tr_98bw.pdf

THE EFFECTS OF OXYGEN-ENRICHED AIR ON FIREFIGHTER JOB PERFORMANCE

Interesting study. This study would suggest that higher concentration of oxygen AT NORMAL ATMOSPHERIC pressure reduce fatigue when maximal aerobic exercise is encountered.

This would mean that even without risk of DCS or subclinical DCS, human experiences less fatigue when forced to perform strenous activity.

Since it was double blinded using 17 participants, this study would contradict the only study disputing the beneficial effect of nitrox on divers having only 11 participants who were not pushed to the limit.

 

[amascuba]

Interesting study. This study would suggest that higher concentration of oxygen AT NORMAL ATMOSPHERIC pressure reduce fatigue when maximal aerobic exercise is encountered.

This would mean that even without risk of DCS or subclinical DCS, human experiences less fatigue when forced to perform strenous activity.

Since it was double blinded using 17 participants, this study would contradict the only study disputing the beneficial effect of nitrox on divers having only 11 participants who were not pushed to the limit.

Not necessarily. Scuba diving and firefighting are two totally different activities with different effects on the body. I don't think that you can compare the two activities, while breathing nitrox.

 

[fisherdvm]

Not necessarily. Scuba diving and firefighting are two totally different activities with different effects on the body. I don't think that you can compare the two activities, while breathing nitrox.

Understood very well. That's why I emphasized that the firemen were exposed only to normal atmospheric pressure, not supra-physiologic atmostpheric pressure like scuba diver.

The point here is to say that since firefighters are not at risk for DCS, the anti-fatigue aspect of nitrox might be due to other mechanisms than due to nitrogen bubbles that divers experienced.

There is something else going on here than nitrogen bubbles ....