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Decompression sickness (DCS) in breath-hold divers

trux

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Dec 9, 2005
6,522
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F:Lyon / CZ:Prague
apnea.cz
There is a new study about DCS at freedivers, that was published in the last days:

Decompression sickness in breath-hold divers: A re... [J Sports Sci. 2009] - PubMed result

Although it has been generally assumed that the risk of decompression sickness is virtually zero during a single breath-hold dive in humans, repeated dives may result in a cumulative increase in the tissue and blood nitrogen tension. Many species of marine mammals perform extensive foraging bouts with deep and long dives interspersed by a short surface interval, and some human divers regularly perform repeated dives to 30-40 m or a single dive to more than 200 m, all of which may result in nitrogen concentrations that elicit symptoms of decompression sickness. Neurological problems have been reported in humans after single or repeated dives and recent necropsy reports in stranded marine mammals were suggestive of decompression sickness-like symptoms. Modelling attempts have suggested that marine mammals may live permanently with elevated nitrogen concentrations and may be at risk when altering their dive behaviour. In humans, non-pathogenic bubbles have been recorded and symptoms of decompression sickness have been reported after repeated dives to modest depths. The mechanisms implicated in these accidents indicate that repeated breath-hold dives with short surface intervals are factors that predispose to decompression sickness. During deep diving, the effect of pulmonary shunts and/or lung collapse may play a major role in reducing the incidence of decompression sickness in humans and marine mammals
Some other latest freediving-related scientific studies are listed here (listed in descending order by the date it was added to Apnea Media Base): medical @ APNEA.cz

EDIT: And here, there is the list of other freediving DCS related documents: http://apnea.cz/?DCS
 
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hteas

Well-Known Member
Mar 9, 2005
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Anchorage, AK
Trux,
I just finished reading "The Breath-hold Diving 2006 Workshop Proceedings", jointly sponsored by DAN and thye Undersea Hyperbaric Medical Society. The discussed a very interesting idea at the end of the proceedings about DCS. There were suggestions that freedivers don't get typical cases of DCS, although it may be happening. They were more worried that bubbles forming in the veins on surfacing are captured and held in the lungs. On the next dive the bubbles are recompressed and become small enough to pass through the lungs, through the heart, and on to the brain, where they are captured and grow as the diver resurfaces, something that does not normally occur in Scuba cases. It is an interesting explanation for the atypical cases, such as Taravana. it also suggests that freediving cases maybe much more serious than for Scuba divers

btw: really excellent dialog with Rudi on the Yasemin/FREE discussion
 
OP
OP
trux

trux

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Dec 9, 2005
6,522
760
268
F:Lyon / CZ:Prague
apnea.cz
A new freediving DCS case study from Japan:

Neurological decompression illness in a J... [Rinsho Shinkeigaku. 2012] - PubMed - NCBI

We report a Japanese breath-hold diver (Ama) who presented neurological disorders after diving. He repeated diving into 25-30 meters depth in the sea for 6 hours. After diving, he felt dizziness and unsteady gait. Neurological examination showed left quadrant hemianopia, bilateral limb ataxia and ataxic gait. Head CT revealed gas bubbles in the left parietal lobe. In CT scan on 3 days after onset, gas bubbles disappeared and low density areas were observed in the bilateral parietal lobes. Brain imaging (DWI, T(2)WI and FLAIR) demonstrated high intensity in the parieto-occipital lobes. Neither pulmonary barotrauma nor intracardiac shunt was detected. He was diagnosed as having neurological decompression illness and therefore underwent hyperbaric oxygen therapy. The pathogenesis of this case was considered to be microbubbles induced by decompression. The present case suggests that repetitive rapid surfacing from the deep sea causes neurological decompression illness even in the breath-hold diver.
 
Mar 20, 2011
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Los Angeles
I have had taravana symptoms a few times after a day of recreational spearing, probably four or five times in my life. I have never had numbness but have at the worst times experienced confusion and vertigo for some hours following the diving. Milder instances are usually marked by anxiety and difficulty concentrating for up to 24 hours after the dive, and the difficulty concentrating was only noticed when the next day I was working on something that required a level of analytical thinking that is ordinarily not too difficult for me but on that day was just not happening...

The last time it happened I was not diving deep but it was a day when conditions were spectacular and I was having too much fun... 50' - 60' dives with finning along the bottom for probably 5 or 6 hours, short surface interval. I was ascending very slowly but I suppose I was just spending too much time on the bottom. Last trip where I was doing deeper serial dives I didn't have any problems but I kept a significantly longer surface interval--every time I felt ready to dive again I would check in with a watch and wait at least an additional 60-90 seconds. I typically never look at a watch when I am in the ocean.

I should get a dive watch so that I can record my dive profiles but have my sights set on a Galileo since HR is interesting to me... but I NEED a nice monofin, which is also money I don't need to spend, so I might have to wait on the dive watch....
 
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Mullins

Well-Known Member
Mar 4, 2004
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Wellington, New Zealand
Visit site
More likely you were just dehydrated and/or tired Lance. Thousands of people around the world do that kind of diving all the time. I expect the Ama divers in that article, aside from diving deeper, were diving variable weight with long bottom times and very fast ascents.
 

chrismar

Well-Known Member
Aug 15, 2007
740
73
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New Zealand
In the Solomon Islands, my buddy and I did close to 2 hours underwater with dives between 20 and 37 meters and bottom times between 1:30 and 2:40. We were diving for six days like this and experienced no symptoms. Well, we were tired and lethargic on land, but I'm pretty sure that wasn't the DCS talking.

I know it's possible for some people to give themselves DCS doing constant weight diving, but I honestly think that unless you have an underlying condition that exacerbates DCS, it's VERY hard to do. VWT though? Pretty sure I could do that.
 
Mar 20, 2011
704
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Los Angeles
More likely you were just dehydrated and/or tired Lance. Thousands of people around the world do that kind of diving all the time. I expect the Ama divers in that article, aside from diving deeper, were diving variable weight with long bottom times and very fast ascents.
Not so much dehydration as I am very careful there and, especially when on a boat, pretty well hydrated and topped off with electrolytes, etc. Perhaps it was fatigue... There is a correlation between cortisol and extremely intense exercise/physical stress, and the times I felt most out of whack I was diving harder than ever before, and the last time I felt like that I had been out of the ocean for weeks prior due to injury. Strange though to have difficulty concentrating the next day.
 

Deano 647

Member
Jul 29, 2019
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Not so much dehydration as I am very careful there and, especially when on a boat, pretty well hydrated and topped off with electrolytes, etc. SNIP
It's well accepted in in rec/tec/ diving that divers will commonly surface with what we term 'sub-clinical DCS' Micro bubbles always form in any SCUBA dive, its is the extent and size of them that is critical to other that proceeds to symptomatic DCS. Some hyperbaric doctors postulate that the typical subclinical symptoms which are undue tiredness, lethargy, inability to concentrate and mild rise in temperature may be die to the body's complement reaction. The micro bubbles are perceived by the boy's immune system to be 'invaders' and do what they do, attempt to deal with them by attacking them via the various complement reaction pathways and raising your body temperature to destroy them. I have felt this myself on occasions.

If it can happen to SCUBA divers I am sure it can happen to BH divers, who unlike SCUBA have VERY rapid ascents which would tend to excite micronuclei and microbubbles. Certainly with SCUBAit is well accepted that you do not 'bounce' dive or especially free dive immediately after surfacing from a SCUBA dive. That practice is likely to give you aDCS hit because you have effectively made your own PFO. Here's what happens;

The SCUBA diver surfaces with a greater than ambient gas load of nitrogen in their tissues which takes time to return to normobaric levels, which is why repetitive same day dives are 'penalised' by the algorithm in dive computers. So the diver hassle level of bubbles in the blood, but as long as he stays on the surface, they will make their way back to the heart, then to the lungs were they will be scrubbed, CO2 and nitrogen diffuse out of the blood in tot eh lungs and are breathed out, oxygen diffuses into the blood where it is then carried back the heart and thence into the arterial system around the body (crucially) including the brain.

BUT, if the diver was to immediately resubmerge ("Hey Divemaster the anchor is stuck, can you drop down to 30m and pry it loose?") He is now going to RECOMPRESS those bubbles, to a smaller size when he returns immediately to the surface it is giving yourself a homemade PFO. The bubbles in the venous side compress enough to get past the lungs and then will re-expand on the arterial side and lodge in the worst places, the spine and brain blood supplies.

Freedivers do not get the gas load that SCUBA generates, but SCUBA only do one descent and one (slow) ascent. We Freedivers might do 20-40 of each and the ascents are as fast as we can. This may be exciting micronuclei into micro bubbles, which of course tend to grow.In ALL people, the bubbles continue to grow in size after the pressure is off. They accumulate like gas into themselves from the surrounding blood or tissues (if there are bubbles in the tissues or injury sites) and they grow bigger. This is why SCUBA divers often feel pain later rather than earlier if the bubbles are in joints or tissues (Type 1 DCS) they get bigger before they begin to shrink. Whereas Type 2 hits (cerebro-spinal) manifest so much faster
 
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