Question Deserved DCS hit even with deco cleared due to high exertion during the dive?

[Alex Ouroboros]

Very similar to an experience I had and just described on the post where someone was asking about consequences of omitting deco time,,,
Needles to say, you are quite right in my opinion, Dehdration I would think is root cause, compounded by the lifting and exertion later on,,, I will say that you will probably find it’s both these factors combined that gave you what I would describe as an “edge of a bend” I know it sounds like I’m trivialising it and that’s not really what I’m doing it’s what you got there,,
I also notice you are slightly aware of your exertions underwater, which I also have had thoughts about when in the past I’ve had niggles, and from a purely personal point of view I think I agree with you, after such a brush myself I started to question exertion underwater as a contributing factor on the basis that if your breathing a little harder and blood pumping a little quicker surley from a scientific point of view more nitrogen is being exposed to the lungs volume wise, and on ascent it’s not always the same. So the algorithms and deco maths don’t take that fully in to account, bear in mind all the tables are based on tests done on divers many years ago and where always in the about / ish catagory… I could go on but I’m sure everyone is bored now.

 

[Exxilon]

Hello everyone,
This is my first thread on Scubaboard (had been a lurker for a long time now), and I wanted to discuss a potential case of DCS during a relatively shallow technical dive.
I am a 31-year-old beginner technical diver, with a total of about 200 dives since my certification; and I dive very often in lakes (about 2-3 times per week); during the dive I'll be describing here I had my first "real" experience of a potential DCS after the dive, even if I didn't do any major mistakes (no repetitive dives, no fast ascents, no deco ceiling violations, and so on).

The dive​

A couple of days ago I did a lake dive, using air as bottom gas and EAN50+Oxygen to accelerate deco, with a profile like this one:

• 10 minutes total for the slow descent to about 42 meters (140 feet)
• 20 minutes spent at 42 meters (140 ft)
• 10 minutes to ascent to 21 meters (68 ft); let's say that this is another 10 minutes spent at 30 meters
• switched to EAN50, then spent another 15 minutes at 18 meters (60 ft)
• 10 minutes of slow ascent to 6 meters (20 ft)
• switched to Oxygen, 12 minutes spent at 6 then 5 meters once the ceiling of 6 meters cleared
• short 2-minute extra stop on back gas (air) and slow ascent to surface (2 minutes to reach surface from 5 meters)

For a total dive time of 80 minutes, more or less.
Deco planned using GF 50/80; with the surfacing GF in the pilot compartment being about 68%.
My surface interval before the dive was exactly 92 hours (almost 4 days).

Now, for me, this is a moderately "deep" dive, but I also did several other dives deeper but with less total bottom time (like, 20 minutes at 55 meters (180 ft) or 25 minutes at 50 meters (165 ft)), and always used the same GF settings and surfaced with 70% or less of GF; without issues or strange symptoms.

Symptoms after the dive​

This time, after the dive I was ok, did a quick lunch, and went back home; during the ride home (about 2-3hours after the dive) I started to feel "strange", but at the beginning I blamed the sun (I ate outside during lunch and it was a very sunny day here), and the fact that I hadn't drank a lot of water.

Then, at home (now about 4 hours or less from the dive), I unloaded the doubles and deco tanks from my car and the other equipment, and after a bit started to feel unwell: a bit of dizziness, a general sense of nausea that lasted a couple of minutes, accelerated heart rate.
I then noticed also that I had swollen arms near the wrists (and the wristwatch I had on the left wrist was "compressing" the edema) but I had no itching, no bruises or rashes on the skin (not on the arms, body, back, or torso).

Got tested by a hyperbaric doctor​

I contacted the DAN emergency hotline, and they suggested to go get checked at my local hospital. Thankfully I live about 2km from a large hospital with a hyperbaric chamber available, so I immediately went to get checked and breathed Oxygen during the 10-minute drive.

Note: I also pointed out that I was already tested last year for a potential PFO (transcranial bubble test with just 1 bubble at rest and 3 bubbles after the Valsava maneuver, indicating a potential very small PFO). I got the results checked by a hyperbaric doctor who gave me the green light for technical dives (with no more than a single technical dive per day just for precaution, but this is what I would've already considered anyway)

They tested me with many different kinds of exams, and everything came back clean: ABGA, torso x-rays, standard blood tests, and neurological tests; in addition, I also got checked directly by a hyperbaric doctor to whom I also shared my dive profile.
In the meantime, the swelling in the arms regressed, and the blood pressure and heartbeat went back to normal.

In the end, they diagnosed me with a potential very mild DCS, exacerbated by dehydration (and they prescribed me a series of IV drips to help with hydration).
I avoided a chamber ride, and they suggested I take complete rest for at least 24/48 hours and no altitude change in the following days.

What was different on this dive and why do I think it might be a "deserved" DCS hit?​

After being discharged from the hospital in the late evening, I went back home to rest and started to feel much better, I slept well and the day after took full rest. Today (2 days after the dive) I feel even better.

What I did wrong in my opinion during the dive:

• I swam very fast during the dive, both on the bottom and on the way back (was a wall dive, I turned the dive after about 40 minutes to go back to the shore)
• I spent too much time during the ascent, and I spent about 20 minutes in the 20-15 meters range instead of going up to 6 meters (20 ft).
• Probably I didn't drink enough water both before and after the dive (especially after the dive)
• Even if it's winter here, the day was hot on the surface and I was exposed directly to sunlight for over an hour just after the dive during lunch (this may have worsened the dehydration)
• I didn't account for an extra "safety stop" after the deco obligations cleared, since the temperature of the water was cold (7°C - 44.5 °F), my high exertion during the dive and the long bottom time that probably started saturating also slower compartments.

And, the exertion after the dive (climbing stairs with doubles on, loading/unloading diving gear, etc.) might also have caused my very small PFO to cause a shunt, but it's impossible to know for sure.

Now, my questions:
(And first of all, thanks in advance for reading this long wall of text)

To sum up, what do you think of everything?
Have you ever had a case like this one?
Might it be a mild DCS or the subclinical symptoms I had (without visible skin bends or neurological issues) might indicate that it wasn't a real DCS but more a sum of several things I did wrong during/after the dive?
Should I be worried and change my type of diving, or be even more careful/conservative from now on?

I didn't crunch the numbers on your profile but I assume you were using a computer and/or some kind of ascent protocol since you know you didn't violate a ceiling. Can you tell us more about that?

It's interesting for me to know more about your ascent protocol. How did you determine that? Were there any deviations as compared to normal?

As for your symptoms, I'm happy you're ok. Like you I dive a lot in lakes and often to 50m. Long story short I often surface with a leading compartment GF of about 80 after dives involving 15-35 minutes of deco depending on gasses. I've been doing that 1-2 times a week for 22 years and I've never felt crappy after a dive.

If you surfaced with 68 and feel like you got a hit then IMHO there is potentially more happening here than just a sloppy dive.

I haven't been on Scubaboard for while but back in the day every time someone got a weird hit everyone would wave their hands and wag their heads and chant "PFO", "PFO".....

I don't know and I don't know what the recent fad is, but 68 is just a really low surfacing GF to cause a hit IMO. It might be worth consulting an expert (which is NOT me) about being tested for a PFO.

 

[Duke Dive Medicine]

It might be worth consulting an expert (which is NOT me) about being tested for a PFO.

PFO is associated with sudden-onset severe neurological DCS, inner ear DCS and cutis marmorata (skin marbling). Given the OP's description of symptoms and onset time, a PFO test would not be indicated.

Best regards,
DDM

 

[Comm]

I personally analyzed the EAN50 mix; didn't analyze the last oxygen fill since it was a direct transfill from a 50 liter tank (transfill done by the dive shop).

I know the dive was a little while ago ... but is it possible to test your O2 bottle? Recently I got an O2 bottle from a shop that was not any where near 100%. In that case, someone has originally filled the AL40 with 32% and then topped it up to ~3000 with O2.

 

[Angelo Farina]

Hello everyone,
This is my first thread on Scubaboard (had been a lurker for a long time now), and I wanted to discuss a potential case of DCS during a relatively shallow technical dive.
I am a 31-year-old beginner technical diver, with a total of about 200 dives since my certification; and I dive very often in lakes (about 2-3 times per week); during the dive I'll be describing here I had my first "real" experience of a potential DCS after the dive, even if I didn't do any major mistakes (no repetitive dives, no fast ascents, no deco ceiling violations, and so on).

The dive​

A couple of days ago I did a lake dive, using air as bottom gas and EAN50+Oxygen to accelerate deco, with a profile like this one:

• 10 minutes total for the slow descent to about 42 meters (140 feet)
• 20 minutes spent at 42 meters (140 ft)
• 10 minutes to ascent to 21 meters (68 ft); let's say that this is another 10 minutes spent at 30 meters
• switched to EAN50, then spent another 15 minutes at 18 meters (60 ft)
• 10 minutes of slow ascent to 6 meters (20 ft)
• switched to Oxygen, 12 minutes spent at 6 then 5 meters once the ceiling of 6 meters cleared
• short 2-minute extra stop on back gas (air) and slow ascent to surface (2 minutes to reach surface from 5 meters)

For a total dive time of 80 minutes, more or less.
Deco planned using GF 50/80; with the surfacing GF in the pilot compartment being about 68%.
My surface interval before the dive was exactly 92 hours (almost 4 days).

Now, for me, this is a moderately "deep" dive, but I also did several other dives deeper but with less total bottom time (like, 20 minutes at 55 meters (180 ft) or 25 minutes at 50 meters (165 ft)), and always used the same GF settings and surfaced with 70% or less of GF; without issues or strange symptoms.

Symptoms after the dive​

This time, after the dive I was ok, did a quick lunch, and went back home; during the ride home (about 2-3hours after the dive) I started to feel "strange", but at the beginning I blamed the sun (I ate outside during lunch and it was a very sunny day here), and the fact that I hadn't drank a lot of water.

Then, at home (now about 4 hours or less from the dive), I unloaded the doubles and deco tanks from my car and the other equipment, and after a bit started to feel unwell: a bit of dizziness, a general sense of nausea that lasted a couple of minutes, accelerated heart rate.
I then noticed also that I had swollen arms near the wrists (and the wristwatch I had on the left wrist was "compressing" the edema) but I had no itching, no bruises or rashes on the skin (not on the arms, body, back, or torso).

Got tested by a hyperbaric doctor​

I contacted the DAN emergency hotline, and they suggested to go get checked at my local hospital. Thankfully I live about 2km from a large hospital with a hyperbaric chamber available, so I immediately went to get checked and breathed Oxygen during the 10-minute drive.

Note: I also pointed out that I was already tested last year for a potential PFO (transcranial bubble test with just 1 bubble at rest and 3 bubbles after the Valsava maneuver, indicating a potential very small PFO). I got the results checked by a hyperbaric doctor who gave me the green light for technical dives (with no more than a single technical dive per day just for precaution, but this is what I would've already considered anyway)

They tested me with many different kinds of exams, and everything came back clean: ABGA, torso x-rays, standard blood tests, and neurological tests; in addition, I also got checked directly by a hyperbaric doctor to whom I also shared my dive profile.
In the meantime, the swelling in the arms regressed, and the blood pressure and heartbeat went back to normal.

In the end, they diagnosed me with a potential very mild DCS, exacerbated by dehydration (and they prescribed me a series of IV drips to help with hydration).
I avoided a chamber ride, and they suggested I take complete rest for at least 24/48 hours and no altitude change in the following days.

What was different on this dive and why do I think it might be a "deserved" DCS hit?​

After being discharged from the hospital in the late evening, I went back home to rest and started to feel much better, I slept well and the day after took full rest. Today (2 days after the dive) I feel even better.

What I did wrong in my opinion during the dive:

• I swam very fast during the dive, both on the bottom and on the way back (was a wall dive, I turned the dive after about 40 minutes to go back to the shore)
• I spent too much time during the ascent, and I spent about 20 minutes in the 20-15 meters range instead of going up to 6 meters (20 ft).
• Probably I didn't drink enough water both before and after the dive (especially after the dive)
• Even if it's winter here, the day was hot on the surface and I was exposed directly to sunlight for over an hour just after the dive during lunch (this may have worsened the dehydration)
• I didn't account for an extra "safety stop" after the deco obligations cleared, since the temperature of the water was cold (7°C - 44.5 °F), my high exertion during the dive and the long bottom time that probably started saturating also slower compartments.

And, the exertion after the dive (climbing stairs with doubles on, loading/unloading diving gear, etc.) might also have caused my very small PFO to cause a shunt, but it's impossible to know for sure.

Now, my questions:
(And first of all, thanks in advance for reading this long wall of text)

To sum up, what do you think of everything?
Have you ever had a case like this one?
Might it be a mild DCS or the subclinical symptoms I had (without visible skin bends or neurological issues) might indicate that it wasn't a real DCS but more a sum of several things I did wrong during/after the dive?
Should I be worried and change my type of diving, or be even more careful/conservative from now on?

Thanks for posting your experience. It can be useful for others...
I provide here another possible explanation: you did employ a strongly accelerated deco procedure, involving 50% nitrox and even pure oxygen at 100%.
Although the theory explaining accelerated deco is very old, and it has been widely employed by so-called "tech divers", I did never endorse that theory. It is based on a strongly oversimplified model of the human body.
That model was validated mostly by thousands of dives entirely conducted IN AIR, at a time when even Nitrox-32 for the whole dive was considered unsafe.
So I never trusted these accelerated deco methods. And when using hyperoxigenated mixtures I tend to play it safe, with large conservatorism.
In most cases I use air profile.
So what happened to you seems a fully deserved DCS:
- exertion at depth without using the Scubapro computer (the only one which takes this into account, thanks to its heart rate monitor)
- very aggressive accelerated deco profile with high oxygen
- not conservative settings (GF) on your computer
- small PFO
It looks as the recipe for a perfect storm to me...

 

[Alekseolsen]

It seems like you have a total of almost 10 minutes on air inbetween gas mixes and after going off O2?
At least I've always practiced breathing O2/50% as long as possible, also at the surface waiting for a boat/walking ashore. May give you that little edge at virtually no "cost"

 

[Dr Simon Mitchell]

Hello,

Great thread. After the publication of a landmark study (arguably the most important in the last 20 years) by David Doolette and Greg Murphy less than 3 months ago, events like this should no longer surprise us, and we should definitely stop referring to 'deserved' vs 'undeserved' DCS. This is the reference:

They reviewed their extensive databases of recent US Navy experimental dives and extracted instances of the same diver doing exactly the same dive profile multiple times. Importantly, the repetitions were strictly standardized with respect to factors considered potentially important for risk of DCS like exercise levels, water temperature and thermal protection. After all dives the divers had venous gas emboli (bubbles generated by decompression) measured in a standardized fashion and any cases of DCS were recorded.

What they found was that the same diver performing exactly the same dive multiple times might exhibit extraordinary variability in the numbers of bubbles produced - potentially ranging from none to the highest bubble grade possible despite performing exactly the same dive each time. Importantly, when DCS occurred, it almost always happened when the divers had high bubble grades, which clearly demonstrates that these bubble grades do reflect risk of DCS,

Unfortunately, as per the other thread where I cite an interesting paper from the same issue, I can't share the full paper with you because it is embargoed for members of SPUMS and EUBS until December when it will appear on PubMed Central. However, once again, because of the educational value, I will invoke editor's privilege and share one of the Figures (see below).

The graph shows bubble grade after movement (vertical axis). You can ignore the numbers on the horizontal axis. Each vertical blue line represents a single diver doing the same dive profile, and each dot on that blue line represents the bubble grade after different instances of doing that exact same dive. The divers are arranged in order of highest bubble grade recorded from 'never bubblers' on the left to those who always formed grade 4 bubbles (a lot!) on the right. The red dots are dives where DCS occurred. The key thing to note is the extraordinary variability in bubbling exhibited by some divers. For example, those between ~50 and 70 on the horizontal axis are forming anything between no bubbles and grade 4 bubbles despite doing exactly the same dive. Also, that DCS almost always occurred with grade 3 or 4 bubbles.

After considering these data, it should come as no surprise that someone like the OP can suffer DCS after doing a dive that seems fine, or that he/she has done before. To speak of deserved vs undeserved in this pathophysiologic milieu is just nonsensical.

Its a bit scary actually, because it demonstrates that we are not as good at managing risk by profile manipulation as we think we are. Not saying profiles don't matter - of course they do, but other things are clearly important. The challenge is to figure out what the cause of this variability is!! One of our PhD students is about to embark on a project heading down this track, and others elsewhere are working on identifying unknown risk factors as well.

Simon M

 

[crofrog]

Hello,

Great thread. After the publication of a landmark study (arguably the most important in the last 20 years) by David Doolette and Greg Murphy less than 3 months ago, events like this should no longer surprise us, and we should definitely stop referring to 'deserved' vs 'undeserved' DCS. This is the reference:

View attachment 831314

They reviewed their extensive databases of recent US Navy experimental dives and extracted instances of the same diver doing exactly the same dive profile multiple times. Importantly, the repetitions were strictly standardized with respect to factors considered potentially important for risk of DCS like exercise levels, water temperature and thermal protection. After all dives the divers had venous gas emboli (bubbles generated by decompression) measured in a standardized fashion and any cases of DCS were recorded.

What they found was that the same diver performing exactly the same dive multiple times might exhibit extraordinary variability in the numbers of bubbles produced - potentially ranging from none to the highest bubble grade possible despite performing exactly the same dive each time. Importantly, when DCS occurred, it almost always happened when the divers had high bubble grades, which clearly demonstrates that these bubble grades do reflect risk of DCS,

Unfortunately, as per the other thread where I cite an interesting paper from the same issue, I can't share the full paper with you because it is embargoed for members of SPUMS and EUBS until December when it will appear on PubMed Central. However, once again, because of the educational value, I will invoke editor's privilege and share one of the Figures (see below).

View attachment 831315

The graph shows bubble grade after movement (vertical axis). You can ignore the numbers on the horizontal axis. Each vertical blue line represents a single diver doing the same dive profile, and each dot on that blue line represents the bubble grade after different instances of doing that exact same dive. The divers are arranged in order of highest bubble grade recorded from 'never bubblers' on the left to those who always formed grade 4 bubbles (a lot!) on the right. The red dots are dives where DCS occurred. The key thing to note is the extraordinary variability in bubbling exhibited by some divers. For example, those between ~50 and 70 on the horizontal axis are forming anything between no bubbles and grade 4 bubbles despite doing exactly the same dive. Also, that DCS almost always occurred with grade 3 or 4 bubbles.

After considering these data, it should come as no surprise that someone like the OP can suffer DCS after doing a dive that seems fine, or that he/she has done before. To speak of deserved vs undeserved in this pathophysiologic milieu is just nonsensical.

Its a bit scary actually, because it demonstrates that we are not as good at managing risk by profile manipulation as we think we are. Not saying profiles don't matter - of course they do, but other things are clearly important. The challenge is to figure out what the cause of this variability is!! One of our PhD students is about to embark on a project heading down this track, and others elsewhere are working on identifying unknown risk factors as well.

Simon M

That’s awesome research I can’t wait to read the whole paper.

A few questions if you don’t mind.

Any speculation on what caused the right tail for the always grade 4 bubblers?

Would the data benefit from more resolution? I feel like with some of the machine vision techniques these days it would be easier to measure the bubbles.

If we can now say that vge is correlates to dcs that seems to make something like odive have more value?

Thanks!

 

[dmaziuk]

Also was there anything particular that happened to the one grade 2 DCS case, or was it just an unfortunate statistic?

 

[Dr Simon Mitchell]

That’s awesome research I can’t wait to read the whole paper.

A few questions if you don’t mind.

Any speculation on what caused the right tail for the always grade 4 bubblers?

Would the data benefit from more resolution? I feel like with some of the machine vision techniques these days it would be easier to measure the bubbles.

If we can now say that vge is correlates to dcs that seems to make something like odive have more value?

Thanks!

Hello Crofrog,

These are all very good questions.

In relation to 'always grade 4 bubblers', we have known for some time that there some divers who consistently bubble a lot and some who don't. The short answer is that we don't know why this is. There are some hypotheses, but none proven. Various lines of research are underway in different parts of the world examining things like genetic predisposition (but what do the genes code for!!??). Just as interesting is why the same diver can sometimes produce such wildly different bubble grades despite doing the same dive. Again, a lot of attention to this looking at things like pre-dive exercise, diet / nutrition, hydration etc.

I think you can assume that the bubble grade data are accurate. Essentially all the grading in that large dataset was done by the same (one or two) highly trained and consistent scientists. However, your idea is a good one as a strategy for ensuring grading is consistent (and accurate) with less experienced observers. Automated bubble grading is something that several groups are working on as we speak.

I don't think there has ever been any doubt that bubble grade correlates to risk of DCS, and this study reinforces that. However, it remains a fact that the positive predictive value of a high bubble grade remains poor. In other words, even if you have a high bubble grade, the chances of you suffering DCS are still not particularly high.

Regarding the O'Dive, unfortunately this study really does give pause to question the utility of such a device. The O'Dive considers your dive profile and post dive bubble count in providing advice about adjusting profiles for following dives. However, if bubbling can vary markedly even if you perform identical profiles (as the Doolette study shows) then the premise upon which the O'Dive provides advice is questionable. One could argue that it can only do good if the device advises more conservative diving after a dive in which you produce high numbers of bubbles, and I would not object to that. But given the variability in bubbling after identical dive profiles revealed by Doolette and Murphy, one could not claim that the device can reliably refine dive profiles by using bubble count analysis.

Simon M