Silent Bubbles and Fatigue or Tiredness

[Bopper]

Me: 41yo male, reasonably fit (I go on 25 mile bike rides over hills regularly), 5’9”, 195lbs. I was certified in Jul ’10 and dove wet up until Oct of last year where I started diving dry. I have noticed a slight decrease in fatigue but am still quite ‘sleepy’ after a series of dives (2 or more). No known health issues.

I – like so many other divers – often feel extremely fatigued after a day of diving. Sometimes it occurs the day of the diving, but more often the fatigue will more reliably exhibit itself the day after diving. I’ve always attributed this fatigue to one or several factors: the cold water in Southern California, dehydration, and the effects of nitrogen loading and gas exchanges in the blood.

It’s this last item that I have questions about. Recently while reading the book Deco for Divers, there was a blurb in it about ‘silent bubbles’, or bubbles that are present as a result of supersaturation which inevitably occurs after a dive. They are present but do not cause recognizable symptoms of DCS. However, the book indicated that these silent bubbles may cause a diver to feel fatigued.

So I started dwelling on this idea as a possible cause of my fatigue. I’ve come up with a bunch of questions regarding this subject, and I hope someone can help answer some of them:

• Would an expert conclude that for any diver that has done a significant amount of diving on a single day that the fatigue they end up feeling can be significantly attributed to silent bubbles?
• If silent bubbles do in fact cause fatigue, what is the exact mechanism that causes it?
• If the cause is that they inhibit gas exchange between the capillaries and the alveoli, is it specifically the lack of ‘inbound’ Oxygen or is it the retention of ‘outbound’ Carbon Dioxide, or both?
• Would the presence of silent bubbles register as a decrease in oxygen saturation levels?
• If I purchased a fingertip oximeter and sampled my oxygen level prior to my dive, and then sampled my oxygen after my dive, could a difference in these values be an indication of the effects of silent bubbles on my system?
• If I sampled several dive buddies before a dive and then after the dive, and I consistently showed a higher percentage decrease in oxygen saturation than my dive buddies after a dive, would this be an indication that I am more prone to silent bubbles? An indication that I might have a PFO and they do not?

I know it’s a lot of questions but I think you get the picture of what I’m getting at: I’m trying to deduce if I can pin my post-dive fatigue on silent bubbles and determine if I am affected differently than the general population. Any hints or advice as to how I might do that would be appreciated.

Thank you!

 

[Duke Dive Medicine]

It’s this last item that I have questions about. Recently while reading the book Deco for Divers, there was a blurb in it about ‘silent bubbles’, or bubbles that are present as a result of supersaturation which inevitably occurs after a dive. They are present but do not cause recognizable symptoms of DCS. However, the book indicated that these silent bubbles may cause a diver to feel fatigued.

So I started dwelling on this idea as a possible cause of my fatigue. I’ve come up with a bunch of questions regarding this subject, and I hope someone can help answer some of them:

• Would an expert conclude that for any diver that has done a significant amount of diving on a single day that the fatigue they end up feeling can be significantly attributed to silent bubbles?

Great questions. Re the above: probably not. Fatigue is very subjective and it's also multifactorial - e.g. exercise tolerance, nutrition and hydration can all influence fatigue so I'd say it would be impossible to positively attribute simple post-dive fatigue to silent venous gas emboli. Extreme fatigue, i.e. fatigue that is over and above that expected considering the above factors, could possibly be. However, extreme fatigue is also considered a symptoms of decompression sickness, and fatigue is a continuum. At what point does extreme fatigue go from subclinical DCS to clinical DCS?

Also, if fatigue is the truly the only symptom, it would be very difficult to attribute it directly to bubbles. That's not to say we wouldn't treat a diver whose only symptom on presentation was extreme fatigue, especially if his or her dive profile was provocative; we would examine him/her thoroughly and quite possibly treat for DCS just to be on the safe side.

• If silent bubbles do in fact cause fatigue, what is the exact mechanism that causes it?

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

• If the cause is that they inhibit gas exchange between the capillaries and the alveoli, is it specifically the lack of ‘inbound’ Oxygen or is it the retention of ‘outbound’ Carbon Dioxide, or both?

Please see above.

• Would the presence of silent bubbles register as a decrease in oxygen saturation levels?

If they're decreasing your O2 sat, they're not silent. It is possible for large amounts of bubbles to become trapped in the pulmonary vasculature and cause impaired gas exchange by both direct impingement of blood flow and the ensuing inflammatory reaction, but that would be considered a clinical presentation of pulmonary decompression sickness.

• If I purchased a fingertip oximeter and sampled my oxygen level prior to my dive, and then sampled my oxygen after my dive, could a difference in these values be an indication of the effects of silent bubbles on my system?

Please see above. If you're dropping your O2 sats you should be headed for the hospital.

• If I sampled several dive buddies before a dive and then after the dive, and I consistently showed a higher percentage decrease in oxygen saturation than my dive buddies after a dive, would this be an indication that I am more prone to silent bubbles? An indication that I might have a PFO and they do not?

No. "Silent" or asymptomatic bubbles are just that. Most of the time silent bubbles implies venous gas emboli, or bubbles in the veins that do not cause symptoms but are detectable by Doppler or ultrasound. Silent VGE are trapped by the pulmonary circulation, then gradually reduced in size and eliminated through diffusion. Massive VGE caused by omitting significant decompression would end up in the lungs and probably become symptomatic as described above. 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.

I know it’s a lot of questions but I think you get the picture of what I’m getting at: I’m trying to deduce if I can pin my post-dive fatigue on silent bubbles and determine if I am affected differently than the general population. Any hints or advice as to how I might do that would be appreciated.

Thank you!

Hope this helps! Please post again if you have further questions.

Best regards,
DDM

 

[Insta-Gator]

Might nitrox use on repetitive dives offset fatigue? (I've heard both sides of the placebo effect) However, I would think additional O2 during prolonged exercise could be beneficial.

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[herbdb]

I am an old guy and the family calls Nitrox geezer gas. I use it whenever it is available. With Nitrox, I can do 3-5 dives a day for a weeks vacation without feeling exhausted. It works for me, give it a try.

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edit added

We are heading to the Keys next week for the Lobster mini season. I will be doing six dives a day for the two day season. This will really test my theory.

Might nitrox use on repetitive dives offset fatigue? (I've heard both sides of the placebo effect) However, I would think additional O2 during prolonged exercise could be beneficial.

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[muzikbiz22]

I'm not a doctor, but your symptoms sound normal. Are you getting up at 5 in the morning to rush to get on to a boat, taking motion sickness pills, rocking & rolling on a boat all day, etc ? After a day of diving, I always fall to sleep early and sleep like a baby. Just sayin' While diving itself is not supposed to be exercise, it can be physical. Perhaps look into Nitrox ? I'm of the mind set it makes a difference.

 

[Insta-Gator]

All of us who use EANxx for better NDL generally think it makes us feel better (yup, I'm a geezer) but I was wondering if DDM could factually substantiate our assumptions.

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[Lorenzoid]

All of us who use EANxx for better NDL generally think it makes us feel better (yup, I'm a geezer) but I was wondering if DDM could factually substantiate our assumptions.

If I recall, Deco For Divers mentioned a study that found, after a single dive (and it might have been a chamber dive--not water--but I don't recall), no significant difference in fatigue between air and Nitrox. But that left open the question of repetitive dives over multiple days. I have not heard of a study on that, but it would definitely be interesting. I am a skeptic of the benefits of "geezer gas." I have certainly dived Nitrox over multiple days, but never had the opportunity to do the exact same dive schedule under the exact same conditions with air for comparison.

 

[Duke Dive Medicine]

All of us who use EANxx for better NDL generally think it makes us feel better (yup, I'm a geezer) but I was wondering if DDM could factually substantiate our assumptions.

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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

 

[DocVikingo]

Hi Insta-Gator,

(Courtesy of myself & Undercurrent)

“Does Breathing Nitrox Reduce Post-Dive Fatigue?

from the April, 2011 issue of Undercurrent

Nitrox has been claimed to improve blood oxygen circulation, reduce the severity of a barotrauma and reduce feelings of tiredness or fatigue following a dive. These are only anecdotal reports, and one controlled study with simulated dives in a dry chamber showed no measurable difference in fatigue, attention levels or ability to concentrate. A group of European researchers decided to test the hypothesis that post-dive fatigue is somehow related to decompression stress, assuming that it would be less in Nitrox-breathing divers.

The researchers tested 301 fit divers (204 male, 97 female) over a two-month period at the Red Sea resort town of Sharm- El-Sheikh, Egypt. Visually impaired divers had to wear corrective lenses during dives, and those using medications were excluded. Divers were forbidden from drinking alcohol or caffeine before and after dives. Each diver performed a single dive at least 12 hours after any previous dive, breathing either air or EANx32 (a mix of 32 percent oxygen, 68 percent nitrogen). No dive restrictions were imposed except a maximum depth of 100 feet. All divers did multi-level dives - - the Nitrox group ranged from 45 to 95 feet, with dive times between 32 and 69 minutes, while the air group dived between 40 and 90 feet, with dive times between 31 and 71 minutes. Divers followed their own dive computers (Nitrox divers' computers were set for an EANx32 mix) and were most often limited to a single safety stop of five minutes at 15 feet.

Fatigue was assessed before each dive and 30 to 60 minutes after, with each diver asked to evaluate both their energy and tiredness levels on a scale from 0 to 10. Then alertness was tested using critical flicker fusion frequency --"the frequency at which a stimulus of intermittent light seems to be completely stable to the observer." A waterproof device consisted of a rotating cylinder with a slit that allows the eye to see flickering. As the rotation of the cylinder speeds up, the eye and brain eventually cannot detect the flicker but sees a solid or fused light. The earlier this occurs, the less alertness and the more fatigue the viewer experiences. The test was repeated three times, with the mean value used as the fusion frequency.

The study showed a significant decrease in perceived fatigue in Nitrox divers. The flicker-to-fusion times decreased by 6 percent in the air group but increased 4 percent in the Nitrox group. On the other hand, the difference between breathing pre- and post-dive in Nitrox users was not significant. The critical flicker-fusion frequency measurements showed impairment in air divers but improvement in Nitrox divers. Still, more studies are needed to fully explore the complexity of modifications in the nervous system according to the type of gas used for a dive.

"Evaluation of critical flicker fusion frequency and perceived fatigue in divers after air and enriched air nitrox diving," Pierre Lafere et al., Diving and Hyperbaric Medicine, Vol. 40, No. 3, pages 114-117.—DocVikingo”

Cheers,

DocVikingo

 

[dfx]

Might nitrox use on repetitive dives offset fatigue? (I've heard both sides of the placebo effect) However, I would think additional O2 during prolonged exercise could be beneficial.

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.