Fatigue and nitrox

[Bubbletrubble]

If it's "certainly incorrect" then please explain why and provide at least one study or other relevant link that supports your position that Nitrogen loading during a dive is positively associated with fatigue other than because it seems to make sense to you and/or you feel better after diving with Nitrox as compared to air.

@idocsteve: Ummm. Please read my last post. You made the initial point. I'm calling you out on it. You should be providing proof that nitrogen loading does not cause post-dive fatigue. It's almost comical that you've taken my statement, twisted it around, and are now calling for me to support your twisted version of my statement...not to mention that you either didn't understand the qualifying language I used or chose to ignore it.

I look forward to reading your response.

 

[idocsteve]

@idocsteve: Ummm. Please read my last post. You made the initial point. I'm calling you out on it. You should be providing proof that nitrogen loading does not cause post-dive fatigue. It's almost comical that you've taken my statement, twisted it around, and are now calling for me to support your twisted version of my statement...not to mention that you either didn't understand the qualifying language I used or chose to ignore it.

I look forward to reading your response.

I "shouldn't" have to do ANYTHING, especially prove a negative.

I have simply maintained that it is universally accepted that there is no conclusive evidence that divers who breathe Nitrox are any less fatigued than those who breathe air, all other variables relating to the dive being the same. There isn't anyone on this board or anywhere else who can effectively dispute that.

I then suggest that it would naturally follow, from a commonsense, logistical point of view, that if breathing Nitrox does not decrease fatigue, then Nitrogen loading is not related to fatigue. Because if Nitrogen loading WAS related to fatigue, then divers breathing Nitrox and getting less of a Nitrogen load would be less fatigued and, once again, that has not been statistically proven to be the case.

Listen I can't prove that there's no such thing as Santa Claus or the Easter Bunny or some dude in the clouds with long hair and a beard, but I'll maintain that there isn't until such time as someone who does believe there is provides me with a single shred of proof.

 

[Bubbletrubble]

I then suggest that it would naturally follow, from a commonsense, logistical point of view, that if breathing Nitrox does not decrease fatigue, then Nitrogen loading is not related to fatigue. Because if Nitrogen loading WAS related to fatigue, then divers breathing Nitrox and getting less of a Nitrogen load would be less fatigued and it has not been statistically proven to be the case.

I think you misused "logistical" and meant to say "logical." But then again, a point of view doesn't necessarily have to be logical.

Herein lies the problem with your reasoning. Yes, it is widely accepted that breathing 32% nitrox vs. regular compressed air does not significantly decrease post-dive fatigue. I bold-faced the term "significantly" because you omitted it in your statement above and it really is the key here. You'll agree that regular compressed air has roughly 21% oxygen and 32% nitrox has roughly 32% oxygen. Assuming that the bulk of the remaining gas is nitrogen, there should be more nitrogen in the regular compressed air than in the 32% nitrox mix. It's entirely possible that the differential nitrogen loading (breathing 32% nitrox vs. regular air) simply doesn't provide enough of a statistical difference in diver-reported post-dive fatigue. (Nevermind the difficulty with imposing quantitative measures on something as subjective as reported post-dive fatigue.) This is why your reasoning is flawed. Based on the data we have, it would almost certainly be incorrect to state that nitrogen loading has no bearing on post-dive fatigue.

Listen I can't prove that there's no such thing as Santa Claus or the Easter Bunny or some dude in the clouds with a Beard, but I'll maintain that there isn't until such time as someone who does believe there is provides me with a single shred of proof.

Let's keep Santa out of this, lest he leave a lump of coal in your stocking this year.

 

[idocsteve]

I bold-faced the term "significantly" because you omitted it in your statement above and it really is the key here.

I'd prefer the word "statistically" because "significant" would lead one to believe that there is at least a small measurable difference between Nitrox and air in regard to diver fatigue which has not been proven.

You'll agree that regular compressed air has roughly 21% oxygen and 32% nitrox has roughly 32% oxygen. Assuming that the bulk of the remaining gas is nitrogen, there should be more nitrogen in the regular compressed air than in the 32% nitrox mix.

Yes of course there is less Nitrogen in Nitrox as compared to regular compressed air.

This is why your reasoning is flawed. Based on the data we have, it would almost certainly be incorrect to state that nitrogen loading has no bearing on post-dive fatigue.

I don't see where the fact that there is less Nitrogen in Nitrox than compressed air does anything to bolster your claim that Nitrogen loading has any affect whatsoever on post dive diver fatigue.

 

[Puffer Fish]

I am not a medical doctor! I fix sick Networks. However, I learned something from a Dan presenter a few years ago.

Most recreational divers suffer from Type II DCS (neurological). Marked fatigue is also a symptom of cub-clinical DCS as well as more advanced stages of DCS.

He then went to point out that the half times for blood and neural fluids are pretty similar (3-5 minutes). It is my humble belief that anything to reduce N2 during and after the dive will also reduce fatigue. However, I believe that the rate of ascent has more to do with this than anything else.

If you are diving for 5 cycles, you are 97% saturated which is pretty durn close to being fully saturated. For blood and neural fluids, this is only 25 minutes. If you have spent 25 minutes at 99 FSW, your blood and neural tissues are close to being at 3.16 ATA_N. A three minute stop at 15 FSW will result in you surfacing with 2.17 ATA_N in those tissues.

However, if you did a deep stop of 3 min @ 50FSW and then a 5 min shallow stop at 15FSW then you would surface with 1.65 ATA_N which is a difference of over half an atmosphere. Going the Deep stop route results in having about 60% of the excess N₂ compared to doing only the safety stop.

For 32% the figures would be:

25 min@ 99FSW: 2.72 ATA_N
3 Min safety stop only: 1.87 ATA_N
3 min deep stop & 5 min shallow stop: 1.42 ATA_N
3 min deep stop & 5 min shallow stop on O₂: 0.74 ATA_N

It should be noted here that:

• I am only looking at ONE tissue group (Blood/Neural Tissues) since it's more likely that I will suffer Type II DCS.
• I am using 3 mins as the half time for these tissues. Dr Deco has a lot better data for this.
• I am rounding where it makes sense to me.
• Doing a deep stop with a full five minutes at my shallow stop works well for me. I can stay awake on the drive home.
• I am not a medical doctor.

Nice job on the math. I use a similar plan for the very same reasons.

 

[Reg Braithwaite]

I am not a medical doctor! I fix sick Networks. However, I learned something from a Dan presenter a few years ago.

Most recreational divers suffer from Type II DCS (neurological). Marked fatigue is also a symptom of cub-clinical DCS as well as more advanced stages of DCS.

He then went to point out that the half times for blood and neural fluids are pretty similar (3-5 minutes). It is my humble belief that anything to reduce N2 during and after the dive will also reduce fatigue. However, I believe that the rate of ascent has more to do with this than anything else.

If you are diving for 5 cycles, you are 97% saturated which is pretty durn close to being fully saturated. For blood and neural fluids, this is only 25 minutes. If you have spent 25 minutes at 99 FSW, your blood and neural tissues are close to being at 3.16 ATA_N. A three minute stop at 15 FSW will result in you surfacing with 2.17 ATA_N in those tissues.

However, if you did a deep stop of 3 min @ 50FSW and then a 5 min shallow stop at 15FSW then you would surface with 1.65 ATA_N which is a difference of over half an atmosphere. Going the Deep stop route results in having about 60% of the excess N₂ compared to doing only the safety stop.

For 32% the figures would be:

25 min@ 99FSW: 2.72 ATA_N
3 Min safety stop only: 1.87 ATA_N
3 min deep stop & 5 min shallow stop: 1.42 ATA_N
3 min deep stop & 5 min shallow stop on O₂: 0.74 ATA_N

It should be noted here that:

• I am only looking at ONE tissue group (Blood/Neural Tissues) since it's more likely that I will suffer Type II DCS.
• I am using 3 mins as the half time for these tissues. Dr Deco has a lot better data for this.
• I am rounding where it makes sense to me.
• Doing a deep stop with a full five minutes at my shallow stop works well for me. I can stay awake on the drive home.
• I am not a medical doctor.

I subjectively report a large decrease in sub-clinical DCS symptoms on multiple dive days when I have used Minimal Deco rather than a PADI-style single safety stop. Ratio Deco adherents conjecture that the driving factor is the surface tension of bubbles rather than tissue saturation. Stopping at 50% for a minute is alleged to play a big role in keeping bubbles small.

So... I am just passing along an alternate explanation for why deep stops may help you feel better. I have no idea what is actually going on.

 

[Thalassamania]

As far as I know there are no definitive studies on fatigue and EAN, the two studies that have been done are inconclusive because they represent single exposures to 18m in a dry chamber with a very well controlled ascent, thus having almost nothing to do with reality.

First you need to decide what we are talking about. Diving EAN to EAN limits should be about the same nitrogen load as diving air to air limits, but diving EAN on air tables using air limits will clearly reduce a divers nitrogen load. If fatigue is related to nitrogen load (and I expect that it is, as a result of the temporary loss of gas exchange surface in the alveolar beds due to venous side bubbling) then it stands to reason that anything that reduces such bubbling will concomitantly reduce fatigue. That has been my experience and the experience that I have observed watching innumerable scientists work on many, many projects. When we are diving EAN on air tables lots of things get done in a much more timely fashion, people are less often found in their rack when you need them, paperwork gets turned in more promptly, there is an increased attendance at the evening movies in the mess, the social life on the ship is much fuller and more interesting. These are only anecdotal observations because I never thought to record when exactly when dive logs and dive reports were turned in, something I intend to do at my next opportunity.

Might I suggest that when one can couple even a subjective appraisal of an objective phenomena with a rationale explanation, that rises above the level of the just anecdotal (remember that anecdotal does not mean wrong, it just means that it has yet to be tested with the rigor that hallmarks peer-reviewed science).

My other point is that I have only seen this effect on multi-day, multi-dive operations. It is not exhibited on a short shop to blow off one or two tanks. Most recreational divers will only be in a situation to clearly feel the effects if they are both diving EAN on air tables AND are making on the order of three or more dives per day for three or more days. That's not to say that EAN is not a help on a single dive, just that you are not likely to physically feel the effect on a single dive.

 

[Deep South Divers]

Fascinating subject.

I have always noted that fatigue was a primary indicator for my personal diving that I was pre-DCS and approaching Type I. I figured that it was reasonably believed, and I'm shocked to consider that not everyone is sold on the idea of fatigue as a DCS indicator.

Note that the "London Diving Chamber" lists "General symptoms of profound fatigue or heaviness, weakness, sweating, or malaise" as a primary indicator of DCS at How to diagnose DCI, decompression sickness / DCS / decompression illness / DCI / diving and the bends, London Recompression & Hyperbaric facilities - The London Diving Chamber . Wikipedia explains that a general symptom is "Unexplained extreme fatigue or behaviour changes" but cites that "extreme fatigue" is present in less that 2% of subjects studied. This is at Decompression sickness - Wikipedia, the free encyclopedia . EMedicine cites a symptom of DCS as "◦General symptoms of profound fatigue or heaviness, weakness..." at Decompression Sickness: eMedicine Emergency Medicine . There are dozens of other references to a connection to DCS and fatigue on Google.

Now, having said that, obviously, just because it's on the Internet doesn't make it so - and I am hard-pressed to find a conclusive study on the subject.

Having said that, however, and because during my studies at Duke University's Hyperbaric Facility (I was a test subject, not a doctor), I got the impression that it was generally accepted that fatigue could be used as an indirect indicator to pre-DCS. It's worked for me over the years - feeling tired and heavy and basically horrible (I liken it to the first day of catching the flu, prior to becoming symptomatic) basically tells me that I'm too close to actual, diagnosed DCS. In other words, that I need to "cut back" on my saturation levels.

The ways to do that, obviously, are by reducing my nitrogen exposure... In other words, by breathing elevated oxygen mixes and/or flattening my ascent rates.

I guess what I'm saying is that for me, my experience has been that yes, nitrox can have a pretty dramatic effect on my general state of feeling at the end of a long dive day... But not really until I'm near my limits. If I did a dive to 60 feet for 5 minutes, then whether I was on air or EAN36 I wouldn't be able to tell the difference. If I did a dive to 60 feet for 60 minutes, however, I can tell a huge difference. It's a matter of saturation levels.

Of course, this is a totally unscientific observation - but a real observation nonetheless, and no, it's not a placebo effect.

I'm shocked to find that there are people who do not generally accept the theory that reduced nitrogen exposure reduces fatigue while diving.

I always assumed that the fatigue was caused by my body fighting "invading" microbubbles... Which would cause fatigue for the same reason that an invading virus causes fatigue in the body.

On a side note - someone mentioned a PFO... The real problem with a PFO isn't that the arterial and ventrical blood mixes... It's that bubbles in the bloodstream can "leak" through the PFO and therefore never make it to the lungs for dispersal. Those with extended PFOs are dramatically more susceptible to DCS.

At Duke, testing negative for a PFO was foremost on the requirements for entry.

 

[MaxBottomtime]

Before I took up diving I used to do a lot of backpacking. My pack usually weighed about 35 pounds. After a day of mountain climbing I was exhausted. I began diving and suddenly found myself carrying 80-120 pounds of gear on my back, hiking in a drysuit and entering surf from a rocky beach. After spending 60-120+ minutes in 50F water +- a few degrees, I would climb back out of the water, up the hill and plop down on the tailgate of my truck. I feel the same after a dive no matter what gasses I use.

 

[islanduni]

It's simple, just breath pure o2 for 20 minutes at the end of the day and you'll feel great! If that's not working contact NUVAIR and ask for Glen.