do "undeserved" hits happen

[gcbryan]

I think that in your other post where you raised this question and got the answer that there are no undeserved hits the point was really a matter of semantics...your body deserves to take the hit but you just don't know why. You in this case meaning any of us. It's not undeserved in the sense that there is some magic involved it's just that we have incomplete knowledge of all the factors.

In the sense that you are using it I think most people agree there are undeserved hits meaning that we did everything we knew how to do and still got hit.

Some hits are more deserved than other however. If someone stays within the NDL's but is out drinking every night and isn't getting much sleep either a hit might not seem so undeserved for anyone who tries to keep up with current deco theory. Other cases would baffle anyone but one could argue it's not undeserved...we just don't understand why it was deserved...semantics.

 

[boulderjohn]

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

YES!

The problem is that I don't believe we really know what it means to do everything right.

Do you mean following a profile specifically approved by some agency or computer algorithm? If so, how do we know that those are right?

To give you an example from the world of technical diving, my buddy and I were in a situation where we were side by side for an entire dive (using helium). It was not a long or deep dive by any means, and the only reason we were using a helium mix was because it was the only thing we had with us at the time. When we ascended, I assumed we were within no deco limits, and his computer agreed--no stop time required at all. My computer called for 15 minutes, because the designer of my computer software had a totally different opinion about helium than the designer of his computer software.

In the long run, we are really taking an educated guess about what is right.

 

[Kevin Carlisle]

Cant be a yes answer because its all a theory. So there is no undeserved hits, just bad luck if you followed the rules.

 

[Akimbo]

…If someone stays within the NDL's but is out drinking every night and isn't getting much sleep either...

You are describing the standard condition of human subjects the US Navy tables were developed under!

I can’t remember the name of the bar near the Washington Navy Yard when the Experimental Diving Unit and First Class Diving School was there, but they had the coolest collections of bronze Navy diving plaques, patches, and decals I have ever seen. I am probably wrong, but I think there was a sign near the door that said: "No common air breathers allowed" — referring to HeO2, not Nitrox. I wasn't 21 yet and didn't have any money anyway so didn't get to spend much time there. I wonder if they moved to Panama City with EDU? It seems like it was just over a bridge… on the opposite side of the Anacostia??? It looked like it had been there a very long time.

 

[Superlyte27]

lol, I dove with that group Akimbo... we cured that prior to beginning every dive. I still can cure any hangover in 30 minutes or less, guaranteed.

30 minutes in a chamber on O2, drinking a large bottle of Pedialyte.

 

[MXGratefulDiver]

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.

You are looking for a simple answer to a complex question ...

... Bob (Grateful Diver)

 

[Crush]

You are looking for a simple answer to a complex question ...

... Bob (Grateful Diver)

Undoubtedly so.

However, to use an analogy, I think of undeserved DCS hits as winning the lottery. Now, it may be possible to win the lottery, and it happens to someone every week, but the probability of your winning the lottery is usually quite low.

 

[MXGratefulDiver]

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 couldn't disagree more with what you said.

If something bad happens to you, it happens for a reason. You may not know or understand what the reason is ... but that doesn't mean it's just bad luck, or your day to get bent, or the tooth fairy made you do it, or whatever imaginary excuse you can come up with. It happened for a reason.

There are way more variables involved in decompression than your dive computer or table is designed to handle. Your computer, your tables, your "ascent system" knows nothing about your physiology, your age, your health, your fitness level, what you had to drink last night, how much sleep you got, or a whole raft of other things that affect your body's ability to offgas efficiently. It doesn't know how hard you exerted yourself during the dive or whether you are dressed appropriately for the water temperature ... do you have any notion what happens to your circulation when you get cold?

Hits happen for a reason ... that's what people mean when they say there are no "undeserved" hits. The more you learn about decompression the more you realize your body's ability to offgas without notable symptoms of DCS is determined by a complex interrelation of variables that your computer or dive table simply doesn't consider.

Dive tables and computers work for one simple reason ... because they have so much conservatism built into them that they reduce the risk to an almost infinitesimally small number ... but it is not, and never will be, zero.

Every time you get in the water there is a finite chance that you will get bent. By virtue of the fact that you made a conscious decision to go diving, if you get bent it is because you put your body in a place where such an effect was possible. In that respect, it is not "undeserved" ... you just gambled and lost.

... Bob (Grateful Diver)

 

[TSandM]

You know, I found the "Mysterious Malady" DVD from GUE to be fascinating to watch. The DVD is a compilation of interviews with a number of people who are involved in what science is being done today to study decompression, and to a man, they agree that the phenomenon is not fully understood.

Our tables and decompression programs are mathematical models, and like all models, they are only as good as our understanding of the variables that affect the underlying system being modeled. We don't understand this one fully. When someone gets an "undeserved" hit, all that means is that an unidentified variable came into play in that case. Whether that's the state of hydration, or the state of the diver's fitness, or the state of the water, or the state of the union . . . the fact is that we don't know what the variable is, so we cannot account for it in our models.

I would imagine that, in part BECAUSE we are so successful in reducing the rate of DCS with our current diving parameters, that it is difficult to analyze the cases (given that they occur in different places, under different conditions, to different people, and are probably reported in different degrees of detail) to try to identify what, if any factors are not unusually considered but found in common with all the "undeserved" cases.

 

[Crush]

I just googled "undeserved DCS" and found something. In this article: DAN Divers Alert Network : Unexpected Decompression Illness DAN has recognized that what I referred to as "undeserved DCS" does exist, however instead of referring to it at "undeserved DCI" or "unpredictable DCI" they chose the term "unexpected DCI" because it has neither statistical nor stigmatizing implications.

One notable observation in the article referring to cases of "unexpected DCI" was:

These divers were well-rested, well-hydrated and physically fit; they stayed within the limits, made a controlled ascent in the chamber and had a non-stressful, non-demanding dive at rest. They followed all the rules, but they still experienced decompression illness. Why? DCI is still a mystery in many ways: we do not yet understand why some individuals follow the same dive profile and get DCI one day but not the next. The cases involving individuals who do not follow the "rules" - those divers who overstay their limits, ascend too rapidly, have other health problems or party too hard the night before - are easier to understand.