Silent Bubbles and Fatigue or Tiredness

[Insta-Gator]

In my completely unprofessional opinion, I'd say you already have additional O2 available on every dive. Namely twice as much at 33 fsw, three times as much at 66 fsw, etc, since it depends on the ppO2. In other words, you'd have the same amount of O2 available at 33 fsw on air as you'd have breathing 42% nitrox at the surface.

According to your statement my nitrogen would go up also, if I understand your intent properly. Ergo my percent of O2 would not go up due to increased pressure. No value

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[dfx]

According to your statement my nitrogen would go up also, if I understand your intent properly. Ergo my percent of O2 would not go up due to increased pressure. No value

Yes, but N2 is an inert gas. It doesn't bond to red blood cells and so it doesn't get in the way of the O2.

 

[Lorenzoid]

There's some data out there:

Evaluation of critical flicker fusion freq... [Diving Hyperb Med. 2010] - PubMed - NCBI

Effects of successive air and nitrox dive... [Eur J Appl Physiol. 2012] - PubMed - NCBI

Could someone translate their conclusions into layperson English? Is there strong evidence that people feel less fatigued diving Nitrox instead of air on a typical set of dives?

The Undercurrent article by DocVikingo at least includes this clear sentence: "The study showed a significant decrease in perceived fatigue in Nitrox divers."

 

[Duke Dive Medicine]

Could someone translate their conclusions into layperson English? Is there strong evidence that people feel less fatigued diving Nitrox instead of air on a typical set of dives?

The Undercurrent article by DocVikingo at least includes this clear sentence: "The study showed a significant decrease in perceived fatigue in Nitrox divers."

Hi Lorenzoid,

You basically summarized the Lafere study from 2010 that I linked and Doc expanded on... divers reported less fatigue when breathing nitrox. I don't think they were blinded, though... @DocV, do you know? If the divers knew which gas they were breathing it could introduce some bias.

The Marinovic study from 2012 looked at bubble load and behavior of blood vessels in divers in a hyperbaric chamber using air vs. nitrox. One of the points from that study was that air divers had a higher post-dive bubble load than nitrox divers on an equivalent dive. The study also addressed the behavior of the arteries in the divers. It found that nitrox reduced flow-mediated dilation (FMD), or dilation of arteries due to blood flow. We know that hyperoxia results in peripheral vasoconstriction and this study used FMD to measure that effect.

Best regards,
DDM

 

[uncfnp]

So, looking at the Lafere study. It looks like the divers in the nitrox group were allowed to dive their computer's NDL limit on nitrox rather than diving nitrox on air table? That would seem to say that the benefit of nitrox would apply even if you dive the nitrox to NDL?

 

[DocVikingo]

... divers reported less fatigue when breathing nitrox. I don't think they were blinded, though... @DocV, do you know? If the divers knew which gas they were breathing it could introduce some bias.DDM

Morning DDM,

The study specifically states that the researchers were blinded, but makes no such statement regarding the subjects. Perhaps the researchers felt it was unethical or unsafe to deny the subjects knowledge of the mix they were breathing. This certainly would open the door to bias on the visual analog scales, but the CFF, by its nature, would likely be free of such a concern.

Interestingly, the reported effects were found even though the EANx group had, on average, statistically deeper & longer dives.

Cheers,

Doc

 

[uwxplorer]

Did YOU try Nitrox? A number of charter boats offer it in SoCal. I for sure feel the difference. I used to be like you said, tired after a day of diving, but did not experience such problems after I switched to Nitrox (which was rather early on in my diving career as a matter of fact). Final word: I was recently on a boat that was temporary out of Nitrox (banks not functional) and had to dive air. Guess what? For the first time in a very long time, I had to take a nap on the ride back.

 

[Bopper]

Also, if fatigue is the truly the only symptom, it would be very difficult to attribute it directly to bubbles.

Fatigue really is my only symptom. I’ve heard post-dive fatigue described as flu-like symptoms. That’s not how I would describe my experience. There’s no achiness, no joint pains, no difference in respiratory or lung sensation, no congestion in the head, nothing like that. Just a straight I-want-to-lie-down-and-fall-asleep feeling. And the following day after the dive (the following day is usually worse than the actual dive day), my mental abilities seem to be quite dulled. I find my mind not being able to get “traction” and absorb and process things as quickly. Simply put, I’m just kind of “out of it”. Then I’ll get a very good night’s sleep that night and the following day (2 days after the diving) I’ll be at about 90%-95% of my mental peak performance (from what I can tell; co-workers might disagree). I’ll be back to 100% 3 to 4 days after.

(I should mention that on multiple-dive days I expect to get a headache by the end of the day. I’ve gotten these headaches for as long as I remember and am not too worried about them as I did receive a cat scan about 10 years ago and it showed nothing abnormal)

It's probably an inflammatory reaction, similar to the fatigue that you feel before getting the flu or a cold.

Ah yes. I do remember in Deco for Divers the Author explained that bubbles cause problems two different ways: they block blood flow through the capillaries and – amazingly - they trigger a response from the immune system (which causes the inflammation). It’s crazy to think that white blood cells are ‘attacking’ inanimate things like bubbles. The human body is amazing…and a little crazy.

PFO is associated with sudden-onset severe neurological DCS, inner ear DCS and cutis marmorata, likely related to direct impingement of arterial flow by VGE that get into the left side of the heart through the foramen ovale then move on to the arterial circulation. That's a different mechanism altogether.

My logic was: I seem to be affected by fatigue more than my dive buddies (who dive similar profiles) > Therefore I must have something intrinsically different > It must be that I have a PFO and they don’t. But I can see that this logic doesn’t stack up.

One thing I plan on doing to reduce fatigue is to incorporate a 5-minute safety stop instead of 3 minutes as well as reducing my ascent speed - maybe to as low as 10ft per minute.

BTW, on my last boat dive trip I used Nitrox. I ended up getting my expected headache, slightly sea sick, puking, and doing only 3 out of 5 possible dives. (I don't blame these things on Nitrox at all).

Hope this helps!

Best regards,
DDM

Yes it certainly does. Clears up a lot of things. Thank you!

 

[Duke Dive Medicine]

Morning DDM,

The study specifically states that the researchers were blinded, but makes no such statement regarding the subjects. Perhaps the researchers felt it was unethical or unsafe to deny the subjects knowledge of the mix they were breathing. This certainly would open the door to bias on the visual analog scales, but the CFF, by its nature, would likely be free of such a concern.

Interestingly, the reported effects were found even though the EANx group had, on average, statistically deeper & longer dives.

Cheers,

Doc

Thanks Doc, well-put as always.

---------- Post added July 19th, 2013 at 12:39 PM ----------

So, looking at the Lafere study. It looks like the divers in the nitrox group were allowed to dive their computer's NDL limit on nitrox rather than diving nitrox on air table? That would seem to say that the benefit of nitrox would apply even if you dive the nitrox to NDL?

That may be related to a decompression benefit with the higher inspired pO2.

---------- Post added July 19th, 2013 at 12:57 PM ----------

Fatigue really is my only symptom ..... my mental abilities seem to be quite dulled. I find my mind not being able to get “traction” and absorb and process things as quickly. Simply put, I’m just kind of “out of it”. Then I’ll get a very good night’s sleep that night and the following day (2 days after the diving) I’ll be at about 90%-95% of my mental peak performance (from what I can tell; co-workers might disagree). I’ll be back to 100% 3 to 4 days after.

That probably qualifies as having more than one symptom. Fatigue and vague mental status changes are a bit more concerning than fatigue alone. From a diving/diving injury perspective one could categorize those as "constitutional" symptoms.

(I should mention that on multiple-dive days I expect to get a headache by the end of the day. I’ve gotten these headaches for as long as I remember and am not too worried about them as I did receive a cat scan about 10 years ago and it showed nothing abnormal)

There's another symptom. Headache is pretty hard to differentiate (especially sight unseen over the internet) but from a diving perspective it could be anything from dehydration to hypercapnia. It could also possibly be associated with the above mentioned symptoms.

My logic was: I seem to be affected by fatigue more than my dive buddies (who dive similar profiles) > Therefore I must have something intrinsically different > It must be that I have a PFO and they don’t. But I can see that this logic doesn’t stack up.

One thing I plan on doing to reduce fatigue is to incorporate a 5-minute safety stop instead of 3 minutes as well as reducing my ascent speed - maybe to as low as 10ft per minute.

You may just be a bubbler. Some people tend to get higher grade VGE than others who perform the same dives. You might also consider incorporating a deep stop; see the below abstract and paper courtesy the Rubicon Foundation:

[abstract] USE OF A DEEP (15M) AND SHALLOW (6M) STOP FOLLOWING 25 METER NO-DECOMPRESSION DIVES REDUCES DECOMPRESSION STRESS (AS OBSERVED BY DOPPLER-DETECTABLE BUBBLES) WHEN COMPARED TO EITHER A DIRECT ASCENT, OR DIRECT ASCENT WITH ONLY A SHALLOW STOP

Effect of varying deep stop times and shallow stop times on precordial bubbles after dives to 25 msw (82 fsw).

The paper in the second link mentions ascent times. Be careful with slowing your ascents when you're deeper as this can not only slow your off-gassing but also cause some tissues to continue to on-gas. Also, make sure that your regulator is adjusted properly and that you are adequately (but not excessively) hydrated.

Best regards,
DDM

 

[AggieDiver]

In my completely unprofessional opinion, I'd say you already have additional O2 available on every dive. Namely twice as much at 33 fsw, three times as much at 66 fsw, etc, since it depends on the ppO2. In other words, you'd have the same amount of O2 available at 33 fsw on air as you'd have breathing 42% nitrox at the surface.

The comparison is not between a diver diving nitrox and another staying on the surface. The comparison in question is between a diver using nitrox and a diver using air, presumably both diving the same depth profile. In which case, the diver using nitrox is inhaling a higher O2 percentage if they are both at the same depth.