supposed case of neurological decompression illness

[21felix]

Hi @ll,

I d like to share what happened to me two days ago as it really scares me massively!

Ca. 2 min. after surfacing a series of dives I had very strong double vision and another 2 minutes later also very strong vertigo and nausea - I had to be helped swimming out and walking, could only open one eye. Immediate normbaric O2 treatment brought relief after around 30 min. During the 20 min. long transport to a hyperbaric clinic, vision became a bit blurred again and light vertigo set in again. After short clinical examination I received a 2 hr recompression treatment at 2,8 atm with two 45 min O2 intervalls and a 10 min air break.
In general I never dive (deep) dehydrated or really fatigued - on this particular session I had some sore muscles from a workout the day before though. For +60 m dives I usually pack (5 bigger packs, 5 small ones - not yet an uncomfortable pressure in the chest...). My ascent speed is very high (1,4 - 1,6 m/s) although I usually slow down at the last 10 m. The dives were all very fine, not once close to blacking out or lom. After the pressure chamber treatment all symptoms were gone (I was a bit exhausted though). Vision and balance test were all passed even before the pressure chamber treatment (due to normbaric 02 before).
The series of dives I did is as follows:
19 m depth 2:34 min dive time

9 min surface intervall

25 m 0:45

3 min s.i.

45 m 1:20

9 min s.i.

59 m 1:36

21 min s.i.

28 m 0:52

8 min s.i.

68 m 1:55

Two days before the incident I did another series of dives that (maybe?) resulted in another less severe case of supposed neurological DCI. Two hours after the last dive I experienced moderate distortions in vision (could not focus properly anymore) and a one sided, migraine like headache as well as light vertigo. After seeing a hyperbaric physisian and receiving normbaric O2 for 1 h the Doctor told me he believes this to be some form of atypical migraine. After the recommended one day break I resumed diving, ending up having the severe symptoms described above.

The session from two days before:

20 m 2:20

8 min s.i.

20 m 0:32

3 min s.i.

20 m 0:40

3 min s.i.

30 m 1:20 (frc)

14 min s.i.

71 m 1:51

I would be very happy if you guys, especially the experts, could write your opinion about these incidents.
Judging from my experience this should not be able to cause a severe form of DCI, especially since the surface intervalls are not excessively short. I did serieses of dives with 65 m and 70 m dives, friends of mine did 3 (? at least 2) x +70 m within 60 min. and did not display any symptoms. Also the physian that treated me is sceptical about this being a normal DCI - he suspects me to have some organic problem that at least supports this problem (r./l. shunt or the like - what other conditions should be checked?).

Have you ever heard of cases like this? Judging from what I wrote, what recovery time would you think to be adequate (if any opinion on that is possible)?
Is there any data on a higher risk of getting DCI again if one ever had it?

A question that I asked myself alot: Is it typical for freediving that DCI (if it is DCI) emerges in the brain? I thought about that a bit and it would seem plausible judging that the dive reflex causes a vasodilation in the brain, thus saturating especially the tissue in the brain (though on the other hand it would have to be a bloodshift of major extent). Once the pressures decrease while ascending the blood shift is reversed so less blood is available to transport the emerging micro/silent bubbles to the lungs to be filtered out. Therefore, the brain might be the hotspot for DCI in freediving - which would render it an incredibly dangerous sport (even more than it is anyways), at least in deep or repetitive diving. Anyways, I hope my very unsophisticated thought on this turns out to be false.

I ve seen many links to articles but many of them unfortunately require a log in or to buy them for dear money - especially this one seems to be very relevant for me though due to partly similar symptoms (double vision). (http://www.ncbi.nlm.nih.gov/pubmed/20369648)... Any chance I could receive an enlightening pm? ;-)

Somewhere I ve read that double vision was a problem of some aviators in/around WW2 - that would indicate that the ascent speed might have caused the problem... Like written in another thread (http://forums.deeperblue.com/thread...s-dcs-in-breath-hold-divers.84937/#post804344) the speed might have created bubbles that were to big to be transported to the lungs and then, in the next dive, could pass the lungs due to the decreased diameter and thus enter arterial blood, then causing cerebral arterial gas embolism (CAGE). But that again would not explain the first incident with moderately distorted vision setting in around 2h after the last dive!
Anyways, from what I ve read so far I was bloody lucky - as neurological DCI (taking AGE into account as well) can easily result in permanent damages, unconsciousness or immediate death. All in all a very scary experience, that makes me think that (at least deep) freediving might be a (highly rewarding) form of playing russian roulette...

I hope, someone can give a hint on a possible explanation... Also I d be especially thankful if - in case my writing displays any profound misunderstandings - you could discover them by shortly explaining how it really is.

Big thanks in advance!
Felix

 

[trux]

I've been asked by PM to post to this thread. Please keep on mind that I am not a doctor, and even if I were, I could not give any diagnosis remotely. DCI in this case is of course possible, and from my experience rather common under similar conditions, though very individual. Please be sure to have checked previous threads on this topic in the DB archive - there are plenty of good ones with plenty with plenty of valuable information and important advices. Eric Fattah often wrote about his DCI experiences - he seems to be rather susceptible to DCI. It is also very likely many more freedivers experience lighter forms of DCI, but do not recognize them as such. You could also contact directly Dr. Fitz-Clarke, who wrote several important documents on the topic of DCI at freedivers (for example this one is available online: http://www.whoi.edu/fileserver.do?id=60763&pt=10&p=41617).

Eric Fattah believes that the ascent speed is much more critical than surface intervals. He also developed an algorithm to limit freediving DCI used in his Liquivision computers, so you may want to give them a try.

You should also contact Neal W. Pollock at DAN, who keeps data on freediving DCS/DCI and other freediving accidents, and can advise you the closest expert with experience in diagnosing and treating freediving DCI. You should also definitely submit your accident to the DAN Incident Report database at http://DAN.org/IncidentReport

 

[21felix]

Thanks a lot!
The article u linked actually confirms my idea with vasoconstriction leading to the majority of freediving dci being neurological. I try to get hold of the quoted articles as they sound like they re fitting what happened.

 

[efattah]

The profiles you posted would cause me to get DCS 100% for sure. However someone like Will Trubridge could do those profiles without any symptoms. It depends on your susceptibility, and you seem to have a similiar susceptibility to me. You are pre-loading nitrogen on the early dives, then sprinting up from the deep dive, and this combination is the killer. I can get mild DCS from one dive to 65m if the ascent is fast enough. As Trux said you can get a Liquivision Xen ($499) and ask for the freediving DCS software. Set it to conservatism +2 and you will (almost certainly) not have another incident as long as you follow the computer.

Eric

 

[growingupninja]

Ancedotally, ascent speed seems to make a very big difference in DCS symptoms for me when I am doing serial dives. I have never felt like I needed medical attention or been diagnosed but once or twice I had experienced strange dizziness, vertigo, confusion after a day of spearing 25M to 30M.

Since then I adjusted my ascent speed. On deeper dives, I go up slower than any other spearo or line diver I've ever dove with (less than 1M per second, sometimes no more than .75M/sec), and my SI is also much less than anyone I've ever dove with. When we do line training I will typically do 10+ drops to 20M as a safety, plus about 4+ drops to around 30M, and then usually a couple drops to 45M to 50M (over a 2.5 hour session). I sometimes pack for the deepest drops. I am mostly diving/training in cold water (6mm wetsuit) although my episodes were in warmer (75F degree) water.

Glad you are okay.

 

[Mullins]

Middle ear barotrauma is also something to consider. I had a fairly similar experience last year in Niue. My first dive there was to 90m after a flight the previous day. Relatively slow dive, no EQ problems and certainly not difficult. About a minute after surfacing I became dizzy with a slight headache, then my vision went and I lost coordination to the point that I couldn't sit up, let alone stand. Slurring my speech, throwing up and generally not feeling great. Got to a hospital where we insisted they give me oxygen (later found it was set to 5l/min so not doing much good). They did take the DCS suggestion seriously but conferred with NZ docs and decided it was most likely middle ear trauma, in large part because my eyes were able to track diagonally. Gave me a nausea suppressant and something to stabilize the ear membranes. Worked well and I was back to normal a few hours later. No further problems for the rest of the trip.

 

[21felix]

Thanks for the idea! I ll definately take it into consideration, especially because just a week before i had an outer ear baro trauma, bleeding from my right ear (hood squeeze that made a vessel in the ear canal pop but left the eardrum totally untouched - lucky me).
However, there are some questions remaining, rendering it a bit unlikely I think: So you felt absolutely no pain whatsoever? No popping or the like? And you said you were back to normal a couple hours later - I recovered very quickly after breathing oxygen (20-30 min vertigo and double vision were practically gone, little dizziness was the only thing left). And two days before the big problems I had some sort of disturbed vision also, but hours after the dive - and a trauma should cause its effects right away, right?
The whole thing remains a bit mysterious... I ll definately post the results of coming examinations here!

 

[21felix]

What really still confuses me about the whole thing is: both incidents have very similar symptoms but they just dont fit together.

When freediving, we start with an amount of N2 of ~80% of TLC. We dive for a relatively short time, so the only tissue that can be supersaturated is fast tissue - the other tissue is irrelevant. Lets say at a 70 m dive we have tissue that saturates very fast (at the speed of the ambient pressure, like blood does for instance, right?), and a tissue that saturates fast. The former will saturate until the turn, desaturate quickly at the ascent. The latter tissue will be saturated on the ascent as well, for a bit. But it will take up less N2 because it s slower. At some point it will desaturate (that is when the ambient pressure is smaller then the gas tension in the tissue). So it seems unlikely that there is a significant saturation of N2 in freediving in tissue that is not very fast. Even if due to a high ascent rate bubble nuclei or even bubbles form (e.g. from the blood itself) these should not be able to last much longer than the dive time itself. It changes once bubbles are formed because these can only be resolved by diffusing back into the tissue and from there into the blood (oxygen window), what takes more time. But still the bubbles would exist in very fast tissues and thus the rate of diffusion should be high.
Looking at the dive session I did I am pretty convinced that a supersaturation with N2 is very unlikely (and this is what the physician here, Dr. Heikal (he treated some big freediving DCI cases already) as well as Neal Pollock from DAN say). The symptoms appeared after the last dive. Before the last dive there was a 9 min surface intervall, before that a 50 sec dive to 28 m and before that a 22 min break. From all I know after 22 min it is very unlikely that there is any significant N2 left, especially since there were no symptoms at that time (and usually, due to only fast tissue being loaded, DCI in freediving appears quickly from all I ve read). A 28 m dive of less than a minute should not be able to allow any nitrogen load that s still in the system after 9 min (9 times the prior dive time, before that 22 min were ~14 times the dive time of the prior dive). Does that only look unlikely to me? If you can explain to me why it can still be N2 supersaturation I d be very happy to hear that.
So this is where other hypotheses come into play: CAGE due to right/left shunt // PFO or due to bubbles forming directly in the arterial blood or the like. However, although this could explain the second (major) incidence it cannot explain the first incidence as this appeared 2 h after diving. But a CAGE takes max. 15 min until there are symptoms. So maybe these are two incidents independent from each other? Unlikely because both were similar and nothing like this ever happened before...

 

[21felix]

Hi, I d like to share the very insightful answers of Neal Pollock, Research Director of DAN:

First mail:
You have done a good job in summarizing your dives. What is not clear are details of your age, general health and, importantly, your history of previous similar exposures with and without any problems. Also important is clarification as to when the symptoms first developed. After the last dive in the series, or after one of the warm-up dives? The former would be more consistent with possible decompression stress; the latter probably not so. Finally, it may be important when the symptoms cleared. It sounds like it was before treatment in one case, but the pattern is unclear in the other case. All of this information could be important in interpreting your experience.


Based on the current information we have, I am not particularly concerned over your surface intervals. While longer surface periods would provide additional time to equilibrate, the times you described for the shallow dives do not seem unduly aggressive. Regardless of any other observations we might offer, I think that it is important for you to follow this up with your medical monitors to ensure that nothing is missed.


Now to your final questions. Yes, we have heard a number of reports of insults that are at least highly suggestive of decompression-induced events. The fast travel rates associated with modern freediving are so much greater than what is seen in compressed gas diving that we have to be careful not to be blinded by what is effectively a very different experience. The short dive durations and fast travel potentially results in a substantial stress of the fastest tissues, practically, the lung, blood and brain, in descending order. The brain does remain fairly well perfused, encouraging gas uptake during descent and, very possibly, a substantial if short-lived stress during ascent. This kind of pattern would be consistent with transient neurological symptoms. You should not think about a massive reversal of blood flow during ascent, though, or that the diving reflex causes vasodilation of the brain. Think of ascent instead as an important but short-lived period when the rate of pressure decrease markedly exceeds the elimination of accumulated gas. Bubbles could transiently form in such tissues, but continued perfusion (blood flow) could also allow removal of gas quickly enough that any symptoms would usually be fairly transient. In any case, the brain is certainly a critical tissue in deep freediving, and there is no doubt that this adds to the danger, but it is not an unknown hazard, just one often not fully appreciated by participants.


We are just now seeing the emergence of technology that will allow evaluation of very small bubbles forming in tissues other than major blood vessels. What we have now is a logical understanding. The gulf between logic and observed 'truth' should encourage a cautious approach. You should be suspicious of anyone who offers you too confident an interpretation now. 'Truth' is a slippery thing when theory exceeds high quality observations.


Now for practical recommendations. First, make sure that you have a comprehensive medical evaluation to make sure that nothing important is missed, and to have norms established if you continue freediving. Avoid repetitive deep diving (as it looks like you have done according to the information you sent). Extend surface intervals where practical as inexpensive insurance against having a bad day. Reduce your most extreme dives, and advance in small increments of time and depth to minimize the risk of surprises. Finally, make sure that your entire team is aware of potential issues and ready to manage events.

Second mail:
You are welcome to post my comments, preferably not just excerpts, since that often leads to more confusion.
The additional details you provided do not provide any "Aha" insights. You are right that the two hour delay in symptom development is very difficult to reconcile with a freediving decompression insult scenario. The gas load associated with fast vertical travel is far, far more likely to be associated with transient symptoms or, at least those with fast onset. The total gas load is by all logic going to be too small to support a sustained bubble presence. An alternative hypothesis for the problems you experienced could be more compelling.
The range of recommendations for returning to diving after injury reflect the art of medical science. As you will probably appreciate, there are no controlled studies evaluating the impact of various recovery times after various injuries. There are a lot of ethical challenges in thinking about such work. It is best to follow the advice of a physician fully informed of your case and knowledgeable in diving medicine. I might be able to give you some suggestions if you tell me where you will be in Germany.
I will tell you that the delay in returning to diving is not to clear microbubbles. The technology is just emerging that will help us fully understand the micronuclei that appear to facilitate bubble formation. We know that frequent diving can affect patterns of bubble formation, but also that fairly short delays are likely sufficient to restore either the presence or activity level of these constructs. While not specifically relevant to your case, I have attached a recent paper that describes a pattern of bubble appearance that responds to a short course of repetitive daily diving (Zanchi et al. 2013). It might be of some interest.
Reference
Zanchi J, Ljubkovic M, Denoble PJ, Dujic Z, Ranapurwala SI, Pollock NW. Influence of repeated daily diving on decompression stress. Int J Sports Med. 2014; 35: 465-8.



OK, that was it, hope it s interesting for someone!
cheers