do "undeserved" hits happen

[Crush]

Dr. Deco,

I have been on SB for a few years and read many posts on DCS. Some experienced divers believe that truly "undeserved" DCS hits can and do happen. Other equally experienced divers believe that no DCS hit is truly "undeserved" as while the diver may have stayed within NDL, that diver ought reasonably to have know that, at least on that one fateful dive, their body would deviate significantly from predicted behaviour. Reasons for deviation from model-predicted behaviour might include dehydration, fatigue, poor fitness, etc..

In summary, do truly "undeserved" DCS hits happen, or can the diver always be blamed?

 

[Troutmaster]

Subscribed. I know the answer but I don't want to ruin the ending...

 

[Superlyte27]

This is all still theory. A hundred unseen factors contribute to nitrogen loading and offloading. Do you know all of them? Does the computer you are using and the tables you are using take into account how hard you breathed, how hard you worked during or after the dive? Does your computer or tables take into account how much water you drank, whether you consumed alcohol last night or if you are 40lbs overweight?

So... is DCS deserved? Well, who's to say. But certainly, if any of the above apply, you should consider using the conservative mode on your computer, or calculating the next deepest depth on your tables, or more.

DCS is still very hit and miss, everyone's body is different and one computer or set of tables cannot possibly account for all the variations in the human body. My advice is, be conservative if you meet any of the above conditions. 5 Extra minutes is a short time to pay to save thousands in medical bills and hours of time in a chamber.

 

[Crush]

So... is DCS deserved? Well, who's to say. But certainly, if any of the above apply, you should consider using the conservative mode on your computer, or calculating the next deepest depth on your tables, or more.

I have no argument with your post. My question is whether or not a truly undeserved hit is possible. Now, it is possible that one's training was insufficient to teach how to adjust NDL times or profiles based upon fitness level, etc., but I would consider this to be a "deserved" hit as a competent diver ought reasonably to have known what you failed to learn. My question is, can you "do everything right" and still get bent? Based upon my reading in Alert Diver I would say that the answer is "yes, it is possible," but far more experienced divers that I have posted that this is not possible. I am not defending what I have read, either in Alert Diver or in this forum, as I know precious little of dive physiology.

 

[Akimbo]

In my experience, there is no question the answer is yes. I have personally witnessed at least 10 in commercial settings over about 35 years. Surface supplied divers provide the best examples after hyperbaric test subjects. This is because dive profiles are reliable and available due to the diving supervisor's stop watch, ¼% accuracy pneumo-fathometers, log book, and presence of other experienced divers and tenders. Granted, working divers may experience more exertion and get colder than recreational divers, but compensation factors exist in tables for exceptional conditions.

DCS hits to divers who stayed within recommended boundaries are rare and have been becoming rarer since the advent of decompression procedures. Statistical analysis of incidents, and the resulting refinements to procedures, is getting far more complex now that there are so many different formulas and tissue theories. This complication is further exacerbated by decompression computers that allow user selection of conservatism.

This is not to imply that decompression computers are bad for the effort, only that it is a statistical complication for investigators. On the plus side; most computers have log functions that provide an accurate, though usually complex, dive profile typical of recreational dives. Commercial and hyperbaric profiles are typically pretty square compared to the meanderings of recreational Scuba divers.

I don’t want to imply that my reply should cause concern. DCS hits beyond the most mild and usually untreated symptoms are pretty darn unusual in recreational divers. Though I am statistically long overdue, I have never been hit or been with recreational divers who have in 48 years.

 

[Crush]

In my experience, there is no question the answer is yes...

...

I don’t want to imply that my reply should cause concern. DCS hits beyond the most mild and usually untreated symptoms are pretty darn unusual in recreational divers. Though I am statistically long overdue, I have never been hit or been with recreational divers who have.

Thanks Akimbo. If I recall correctly, one article in Alert Diver dealt with the stigma of getting bent and the shame and frustration associated with getting judged for taking an "undeserved hit." Recently I spoke with one diver who stated that he knew lots of divers who routinely got the skin rash associated with DCS, but that those divers rarely mentioned this to anyone outside their closed group for fear of being labeled. There seems to be quite a stigma out there about getting bent.

 

[Troutmaster]

I was gonna wait for the medical experts.....

Yes, you can get an undeserved hit. It happens less now than back in the day, mostly because we know more about deco and the tables and computer models have gotten better. In most non-tech recreational diving you are not likley to get hit if you are following the rules. Those of us on mixed gas and greater depths with serioius deco obligations are far more likely to follow the rules and take a hit anyway.

The divers who say there are no undeserved hits are generally divers who don't know that much about diving physics and who don't want to accept that what we do is dangerous. It is the "it can't happen to me, I follow the rules" mindset. These are the same divers you have a hard time getting to accept treatment during a hit because they have the "it can not happen to me" mindset. I go the other way, if I have anything that might be a DCS symptom or even just feel a little funny, I hit the O2. Its cheap and why carry it if you are not going to use it.

So the simple answer is "yes".

 

[Superlyte27]

I guess the question at it's basic level is: "Can you do everything right and still get bent?"

YES!

 

[Akimbo]

…Recently I spoke with one diver who stated that he knew lots of divers who routinely got the skin rash associated with DCS, but that those divers rarely mentioned this to anyone outside their closed group for fear of being labeled. There seems to be quite a stigma out there about getting bent.

Interesting, but stupid. It is a pretty common belief in the military and commercial diving that the site of untreated DCS injuries are more likely to exhibit future symptoms (usually joints). Skin rash can exhibit as a precursor to more serious symptoms. Divers I have been around are more concerned about their livelihood so are more likely to ride a treatment table than risk permanent damage. You must also consider that there is almost always a chamber on the job and the diver does not have to pay for treatment, beyond maybe loosing some depth pay from lost rotations. This post may help explain.

http://www.scubaboard.com/forums/5272509-post10.html

Edit: I have taken "undeserved" as hits that occur when the diver has not exceeded recommended decompression procedures. Of course today, exceeding the decompression procedures they chose to follow or their computer is programmed for may be a more accurate statement. Then there are the optional safety stops…

 

[Akimbo]

I guess the question at it's basic level is: "Can you do everything right and still get bent?"

YES!

Defining "right" has gotten increasingly squirrelly in the last decade. I doubt that more than 0.1% of divers actively choose their decompression procedure and only 1% know which procedure their computers actually use. I have spoken to entire groups of divers on charter boats that automatically assumed that the tables they trained with were based on, and closely tracked, the same tissue theories that their computers were programmed for.

Considering that through most of my life ascent rates were 60'/minute, there were no safety stops (bumping up one table maybe if you were really worried), and the only option to avoid the decompression penalties of square dive profiles was an analog computer universally called a Bend-o-Matic; maybe it’s not so bad.