DCS Incident - Salient lessons to be learned
- Thread starter Diving Dubai
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Retrospectively perhaps, but not always prospectively. Oftentimes the divers we treat here know exactly what they did wrong and will tell you if you ask them. Sometimes, though, a diver stays within the limits specified by his/her computer, stays adequately hydrated (despite the dearth of evidence linking dehydration with DCS, as several previous posters noted), has a perfectly normal dive and still gets DCS. No decompression algorithm is perfect, and the deeper the dive and the longer the bottom time the more imperfect they become. Do you blame the diver, or do you use it as a lesson to perhaps increase the conservatism setting on the computer or avoid riding the computer on deep dives as flots am pointed out?
Best regards,
DDM
The deco class I taught last weekend ran v planner for all dives. Set at +3 conservatism.
Why? Risk factors that we determined as a group applied.
1. Age - 3 of us near or over 50 was a +1.
2. Cold water (it was 38-40 at depth depending on whose comp you went by) is another +1. That's 2.
3. Then the added stress of a new team doing a technical class with an instructor they had not trained with previously and me having three guys in a tech class was decided to add another level to that.
So in order to create what we decided were safe plans without getting overly conservative we took all this into consideration. No one minded the few extra minutes on the hangs. Gave them time to do things in a thoughtful and non rushed manner. Which is good for divers getting used to proper deco procedures.
It also got them used to looking at the things that could add to the risk of DCS and seeing how changing the settings affect times.
Not mention getting used to the idea that this is a team decision and effort. Not the plans of one person that everyone else has to follow. Too many recreational level instructors don't make students look at how their feelings, ideas, personal comfort, training, and experience should always figure into the dive plan. They get the wrong idea that they have no say. That the guide, DM, or instructor decides what the plan should be.
This needs to change radically. Soon. If you give divers more responsibility I have found that they are more likely to take it and stay involved. The sheep soon wander off to other pursuits.
Why? Risk factors that we determined as a group applied.
1. Age - 3 of us near or over 50 was a +1.
2. Cold water (it was 38-40 at depth depending on whose comp you went by) is another +1. That's 2.
3. Then the added stress of a new team doing a technical class with an instructor they had not trained with previously and me having three guys in a tech class was decided to add another level to that.
So in order to create what we decided were safe plans without getting overly conservative we took all this into consideration. No one minded the few extra minutes on the hangs. Gave them time to do things in a thoughtful and non rushed manner. Which is good for divers getting used to proper deco procedures.
It also got them used to looking at the things that could add to the risk of DCS and seeing how changing the settings affect times.
Not mention getting used to the idea that this is a team decision and effort. Not the plans of one person that everyone else has to follow. Too many recreational level instructors don't make students look at how their feelings, ideas, personal comfort, training, and experience should always figure into the dive plan. They get the wrong idea that they have no say. That the guide, DM, or instructor decides what the plan should be.
This needs to change radically. Soon. If you give divers more responsibility I have found that they are more likely to take it and stay involved. The sheep soon wander off to other pursuits.
As usual, DDM says it best!
"Blame" is a loaded term, but if you stay away from defensiveness and accusatory tone, it's an appropriate one one. DCS isn't a random thing, it has a cause. And as my tech instructor said the first day of class, the cause is always the same - you didn't do enough deco. Now you may have THOUGHT that you did enough, or that a direct ascent was adequate given the NDLs that you calculated with your tables or your computer, but the fact that you got this hit means only one thing - bubbles formed and weren't given enough time to be eliminated. Now, the injured diver has to figure out what that means for them and for their diving future.
Mark Powell, in his great book "Deco for Divers" talks about the bright line through a grey area. I think that if you are going to assume the risk of DCS by breathing compressed gas underwater, you need to understand and accept that.
New divers sometimes think about their dive computers as a "magic bracelet", where if you stay below your NDL it's like a legal contract that you won't get bent, and if you do it's someone else's fault. There is also a lot of talk about buying a more or less conservative computer, as if the algorithm in the gadget on your wrist has direct control over your own risk of injury. Lots to think about, great learning experience, thanks to the OP for posting.
One factoid in the OP's description that may be potentially relevant is that the DM hadn't dived for 4 months or so. There's a phenomenon called DCS acclimatization which can have a significant impact on DCS probability. The DM tried to acclimate a little by doing a couple of practice dives with the OP and his then fiancee, but perhaps not enough. Or, possibly an even more conservative dive plan was called for the actual wreck dive. Again, for any level of conservatism there is a positive probability of getting bent.
Dr. Lecter
Contributor
Thank you very much for your concern.Were you dropped on your head as a child? The point of dive insurance is to cover you should an accident occur, not to have some-heel claims adjuster decide whether you're qualified to dive.
You probably forgot that the DM in this case also had diving insurance and what happened?
Actually, that's user error, not a limitation of software. V-planner is quite capable of planning "non-square" dive profiles if the user knows how to use the program... which isn't that hard.
Regards,
Ray Purkis
OP
Just to quantify the facts from my computer. The Dive was 46 minutes, maximum depth was 29.9m then a climb back to 25m with a gradual ascent the rest of the dive. Average depth was 18.5. You drop down see trucks and carry along the stbd beam (18-22m) as ship is on its side. Minimum NDL on my comp was 6mins. Deep stops and safety (5m) were carried out. None of the 5 computers in our group showed a Deco obligation.
Because we had a second dive on the same boat programmed for that day everyone was mindful so as to ensure the had as much time on the second dive as possible whilst keeping within their limits.
---------- Post added September 21st, 2014 at 05:01 PM ----------
I put that part in to be honest. What I should have added was that we were also drinking lots of water - a fact testified to by a me waking in the night a few times for a bathroom break!
---------- Post added September 21st, 2014 at 05:05 PM ----------
Good point. Our mistake was to assume the dive would be on Nitrox given the depths. It was only when we got on the boat and found air we were told about the special order. Why did we assume? We dive Nitrox which we blend at our club, also every other dive expedition we've been on has Nitrox as part of the trip price. This was our first with a land based operator - Yup our bad and lesson learned. When we went back 3 days later we had ordered the Nitrox.
---------- Post added September 21st, 2014 at 05:12 PM ----------
The point of dive insurance is to cover you should an accident occur, not to have some
The about dive insurance I was trying to make was twofold. Get a decent one and read the fine print. My Dan insurance is very comprehensive BUT it only insures me down to my certification depths - I'm pretty sure if I had an incident outside of my certifications Dan like any other insurance (Stereotyping I know) would dispute my claim?
Hatul
Contributor
Can I ask you what brand computer you and the DM were following?
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