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

[Johnoly]

Yes, never more than 10 meters per second,

LOL,,,Well that's your problem..... You can edit your reply to more accurately state that.

 

[Cragene]

LOL,,,Well that's your problem..... You can edit your reply to more accurately state that.

Well, with a 10 m/s ascent rate would have been more than deserved
Obv. I meant 10 meters per minute, I'll edit the post for clarity.

 

[Duke Dive Medicine]

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?

You may never be able to pin down an exact cause of this DCS event, assuming it's DCS. Decompression algorithms are not iso-risk, that is, the probability of DCS for any given decompression algorithm increases with increasing depth and bottom time. Specific to this dive, heavy work and cold on decompression are both risk factors for DCS.

There's very little empiric data on the effects of different gradient factor settings, so the choice often come down to individual judgement, +- accounting for expert opinion. For instance, you may have chosen a somewhat more aggressive 50/80 to get you out of the cold water more quickly, but where's the sweet spot for your individual physiology for that particular date, time, water temperature, work level, etc, where you can balance getting out of the water to avoid becoming chilled with sufficient decompression to avoid DCS? Were your GF settings appropriate for you for this dive? These are mostly rhetorical questions because I don't know that anyone could answer them accurately, but if your own answer leans more toward an educated guess, that's a data point for you to consider.

Re PFO: First, transcranial Doppler is not able to differentiate PFO from other types of atrial septal defects, though from the amount of bubbles you noted, a small PFO seems more likely. Second, PFO is associated with severe sudden-onset neurological DCS, inner ear DCS, and cutis marmorata skin rash, so absence of a clinically significant PFO doesn't mean you can't get DCS. From your description, your symptoms are consistent with lymphatic DCS possibly accompanied by a sublinical inflammatory reaction to a high venous bubble load, neither of which is related to PFO.

Best regards,
DDM

 

[Imla]

You may want to add a slower ascent from 6m.
Pressure gradient from 6m to surface is relatively large and can be the trigger of slow-tissue bubbles if undertaken too fast. (Especially when you are cold at the end of a long dive)
Try to aim for not faster than 1meter/min up from 6. Challenging buoyancywise, but healthy for both tissues and skills.

I also think you might be underestimating the effect of the long multilevel bottomtimes you had. These longer "shallow deep-dives" can be treacherous.

 

[girlwithbigtanks]

Why did it take so long to get to 140? Was that part of your bottom plan?

 

[Capt Jim Wyatt]

Can you download the dive profile from your Perdix and post the graph here?

 

[Cragene]

You may never be able to pin down an exact cause of this DCS event, assuming it's DCS. Decompression algorithms are not iso-risk, that is, the probability of DCS for any given decompression algorithm increases with increasing depth and bottom time. Specific to this dive, heavy work and cold on decompression are both risk factors for DCS.

I know, in fact, what scared me at first was that there was something wrong with me and it was potentially an undeserved hit, but on second thoughts it can be also due to overly aggressive GF settings for this specific dive, in additional to all other variables related to the dive (exertion, bad hydration, long bottom times, short shallow deco compared to other bottom time, and so on)

Re PFO: First, transcranial Doppler is not able to differentiate PFO from other types of atrial septal defects, though from the amount of bubbles you noted, a small PFO seems more likely. Second, PFO is associated with severe sudden-onset neurological DCS, inner ear DCS, and cutis marmorata skin rash, so absence of a clinically significant PFO doesn't mean you can't get DCS.

Thanks for the explanation, this is very interesting.
I have a friend who a couple of years ago got a very bad "undeserved" hit after a recreational dive (deep to 40 meters - 130 ft, but within NDL limits and with a long safety stop). In his case, the DCS hit just 30 minutes after the dive, with immediate neurological symptoms (severe dizziness and nausea, in addition to impaired balance and vision). He needed an emergency chamber ride followed by a series of additional chamber treatments.
In the end, he was tested for PFO and found out he had a severe, large-sized PFO and he underwent surgery to close the PFO (months later he went back to diving and now everything is ok, thankfully).

From your description, your symptoms are consistent with lymphatic DCS possibly accompanied by a sublinical inflammatory reaction to a high venous bubble load, neither of which is related to PFO.

Interesting, about the possible lymphatic DCS is something the DAN emergency hotline told me; but in that case I suppose I would have had swelling also in the armpits/neck/groin (around the lymph nodes), or not?

Could the swelling in the arms (near the wrists) be related, or that's just due to dehydration?

You may want to add a slower ascent from 6m.
Pressure gradient from 6m to surface is relatively large and can be the trigger of slow-tissue bubbles if undertaken too fast. (Especially when you are cold at the end of a long dive)
Try to aim for not faster than 1meter/min up from 6. Challenging buoyancywise, but healthy for both tissues and skills.

Yes, slow ascents is something that I practice in almost any dive, even recreational ones.
Probably in this case I made a quicker-than-usual final ascent, whereas I usually take 5-6 minutes to exit the water, and also stop for a minute or two at 3 meters (10 feet).

I also think you might be underestimating the effect of the long multilevel bottomtimes you had. These longer "shallow deep-dives" can be treacherous.

Yes, I think I learned the hard way that I should not underestimate "shallow" bottom depth combined to long bottom times, instead of following a more appropriate square profile.

Why did it take so long to get to 140? Was that part of your bottom plan?

Yes that was part of the plan: the wall starts after a slow descent along a sandy bottom, and after 6 minutes or so begins the drop-off where we started our descent.

 

[Cragene]

Can you download the dive profile from your Perdix and post the graph here?

Sure, this is the dive profile graph rendered by Subsurface; the gas switches are EAN50 and Oxygen; the dive starts with Air.

Notes: the sample rate is each 2 seconds (the most informative sample rate available on Perdix), and the last part of the final ascent (where you see some red lines) is because I was at about 1.5m - 0.8m and the Perdix jumped from surface to 1m depending on how I moved my arm in the water.

 

[arkstorm]

Dehydration is a major contributor, well recognized as a root cause in many DCS cases.

Well... perhaps not. Check out this talk about diving myths by Mark Powell at around the 26:00 minute mark...

Being cold at depth then very warm (and exerting yourself) on the surface post-dive would have contributed as well. Both things can increase the rate of bubble formation. This is why there is consistent advice to avoid things like hot showers and strenuous activity after diving.

Again... not so fast. There is evidence that being cold at depth, then warm as you're off-gassing is not problematic. See: Powell Video at 31:40.

As for working hard on the dive itself, I've certainly heard discussion of this increasing DCS risk, but I'm not sure about the mechanism (separate from CO2 issues), maybe some of the dive docs and research people could comment.

Sounds like this one is probably true, at least for the time being. See: Powell Video at 30:30.

My point is that old myths die hard and that everything we think we know and do to avoid DCS is just a matter of risk-management, though not risk elimination.

 

[Duke Dive Medicine]

Interesting, about the possible lymphatic DCS is something the DAN emergency hotline told me; but in that case I suppose I would have had swelling also in the armpits/neck/groin (around the lymph nodes), or not?

Could the swelling in the arms (near the wrists) be related, or that's just due to dehydration?

Lymphatic DCS causes generalized swelling in the area drained by the affected lymph vessels. Swelling can be a symptom of extreme dehydration, but in a young, otherwise healthy person that seems unlikely. As noted by @arkstorm above, dehydration is not the lurking villain that some people make it out to be. Not that divers shouldn't maintain adequate hydration, but it's frequently made the default cause of DCS when another one can't be identified.... "I did everything right but I got bent therefore I must have been dehydrated." That's not necessarily the case. The causal link between dehydration and DCS is not that strong.

I know, in fact, what scared me at first was that there was something wrong with me and it was potentially an undeserved hit, but on second thoughts it can be also due to overly aggressive GF settings for this specific dive, in additional to all other variables related to the dive (exertion, bad hydration, long bottom times, short shallow deco compared to other bottom time, and so on)

An undeserved (now referred to as unexplained) case of DCS does not mean that you made a mistake or there's something wrong with you. It generally means that you experienced DCS despite following your decompression protocol and minimizing known risks. Even if you had done nothing but hover over the bottom and meditate and were toasty warm on decompression, you could have still gotten bent given the background risk of DCS on any technical dive. In your case, heavy work at depth and cold on decompression are known risk factors, and adjusting your gradient factors for a more aggressive decompression profile probably didn't help. Most diving medical people would probably land on the side of an "explained" hit, but even this characterization sounds like victim-blaming, which is not the goal here. There's a common misconception that DCS has an on/off switch and if one just does everything "right", then it won't happen. The question isn't, what can you change to ensure that you won't get bent again. It is, what can you do to best mitigate the risk of DCS.

Best regards,
DDM