Any proof that dive computers improve safety?

[DaleC]

Here's your original post

Folks,
In our age of total statistics, it is easy to find statistical evidence that seat belts save lives, smoking promotes lung cancer, and ibuprofen relieves pain and inflammation.

This is an introductory statement not a question.

However, though dive computers have been around since 80s, I've never seen any proof that using computers actually reduces the risk of injury, especially DCS, in recreational divers.

Still a statement.

I am asking because some dive shops and liveaboards require mandatory dive computers for each diver; however, without solid scientific evidence of safety benefits from using dive computers, I would consider such demands premature. The numbers of decompression cases mentioned in DAN's study here DAN Divers Alert Network : Medical Research : Project Dive Exploration : FAQs are simply too small (only 28 recompressions + 300 mild symptoms like head ache in 10 years) for any conclusions, so I incline to think that no such prove exists.

Still just a statement. You haven't asked a question.

But if someone knows some encouraging stats, please let me know.

Finally the question. And People have been giving you the answer for quite a while now - There are no such stats. You just don't like the fact that a boat operator can make his/her own rules regardless and mistakenly think if you can prove computers are not safer it will invalidate their decision. It won't... it's their boat. It isn't the tool, but rather the operator, that makes the tool safe or not. The computer just allows for easier tracking by a third party and allows for more precise SI's which may be of benefit on a charter.

 

[tarponchik]

Here's a "safety point". A vacation diver goes for a dive and hasn't got a clue about dive planning. Is he safer with a box that says "Go up, you're out of time" or a plastic sheet full of numbers that he hasn't been able to work since OW class 5 years ago?

Terry

You'd be surprised, Terry, but plenty of vacational divers use neither. They just dive with the group from the boat, stay close to DM and go up and down with him. Essentially, the DM is their surrogate tables and computer

 

[tarponchik]

And People have been giving you the answer for quite a while now - There are no such stats.

Thank you for such detailed study of my post. People also said a lot of other things, quite unrelated to the subject. Everybody was trying to be helpful, I certainly appreciate that.

 

[FishOutUvH2O]

Thanks! I understand what you are saying except I think proper words here IMHO would be not "theoretical" but "probability" and "likelyhood of accident." Would you agree?

Not in this case, I wouldn't agree. The calculations that the software is doing are the theoretical on/off gassing of nitrogen, as well as, oxygen loading, and does no statistics. The statistics that determine what the "safe-zone" is were done by people elsewhere (DSAT, NOAA, etc.) and loaded into the computer as a data table. So, the software has no ability to apply the data it's getting from it's sensors (depth, time, water temp. etc.,) and determine the probability that the user is in danger. So, in essence the software is not giving you the probability, or likelihood of getting DCS or O2 toxicity, some researcher is.

But, to answer an earlier question you asked me in a previous post, in the way you wanted it answered. No, I have no knowledge of such evidence that would support your argument.

Regardless, it's been an interesting and somewhat informative (to me anyway) thread.

 

[tarponchik]

You just don't like the fact that a boat operator can make his/her own rules regardless and mistakenly think if you can prove computers are not safer it will invalidate their decision. It won't...

You are certainly correct with the first part (yes, I do not like that), but you are wrong with the second (I am not that dumb). What I was looking for is the justification, like with buckling up the seat belts.

 

[tarponchik]

Not in this case, I wouldn't agree. The calculations that the software is doing are the theoretical on/off gassing of nitrogen, as well as, oxygen loading, and does no statistics. The statistics that determine what the "safe-zone" is were done by people elsewhere (DSAT, NOAA, etc.) and loaded into the computer as a data table. So, the software has no ability to apply the data it's getting from it's sensors (depth, time, water temp. etc.,) and determine the probability that the user is in danger. So, in essence the software is not giving you the probability, or likelihood of getting DCS or O2 toxicity, some researcher is.

But, to answer an earlier question you asked me in a previous post, in the way you wanted it answered. No, I have no knowledge of such evidence that would support your argument.

Regardless, it's been an interesting and somewhat informative (to me anyway) thread.

Probability does not always mean the probability output. If some probability limit is preset as the danger zone by the researcher you mentioned, it is still based on stats. And the comp will say "zero time remains" but not "your chance of getting DCS, if you don't go up in the next 5 min, is 25%, and if you don't go up in the next 10 min, it is 50%" though essentially it means just that, IMHO. If you go up 5 min later it does not mean you have 100% chance of getting DCS, so probably it is still probability.
My pleasure!

 

[AzAtty]

And the comp will say "zero time remains" but not "your chance of getting DCS, if you don't go up in the next 5 min, is 25%, and if you don't go up in the next 10 min, it is 50%" though essentially it means just that, IMHO.

Not exactly; the modeling isn't that precise. In simple terms, modern modelers choose an acceptable level of risk (e.g. 1 in 10,000 dives using the model's profile will result in a Type II DCS hit) and set that point as the model's limit, and then back off of it with some arbitrary degree of conservativism for an added safety margin. In the old days, Haldane used live test subjects and set time limits at points where the subjects did not display overt DCS symptoms. The data simply don't exist to determine the relative probability of a hit if a diver exceeds the model's NDL by a certain period of time. Instead, the data upon which the model is based merely indicate that beyond a certain point, the probability of a hit reaches a level that is unacceptable to the modelers. And sometimes, those data can be sparse.

Also, in response to your original question, there is no proof that diving a computer is "safer" than diving tables. There are no meaningful data on the subject, and the label "safer" is too imprecise for testing purposes. Even a hit/no hit criteria is inadequate because many variables affect DCS and "undeserved hits" occur in every model. Likewise, it is impossible to establish a control group against which to gauge observations because physiology varies from person to person.

 

[DaleC]

You are certainly correct with the first part (yes, I do not like that), but you are wrong with the second (I am not that dumb). What I was looking for is the justification, like with buckling up the seat belts.

The justification of what?

It's their boat - it's their rules. No justification needed. You just don't seem to be able to accept that their real world decision doesn't match your intellectual understanding. Even if you could prove statistically that computers were not safer you still would have to wear one. It's a cruel world sometimes.

But what you really intended to do was to ask a rhetorical question. That is a question that you really never wanted an answer to but rather just asked as a method of espousing your own viewpoint. Your viewpoint is that there is not enough evidence to justify boat operators to require divers to wear computers for the reason of increasing safety.

The confusion is that you have asked a valid question (as I pointed out in my last post) that people have attempted to answer in good faith but instead of acknowledging those answers you continue to assert your rhetorical POV.

Yes, it could be an interesting thread but perhaps you could rephrase your question to eliminate the confusion and not waste peoples time trying to give answers you really do not want.

 

[tarponchik]

It's their boat - it's their rules. No justification needed.

"Not needed" does not necessary mean that no justification exists. For example, the non-smoking rules are also their rules, but are justifyed by fire hazard, foul smells and second-hand smoking complaints.

You just don't seem to be able to accept that their real world decision doesn't match your intellectual understanding. Even if you could prove statistically that computers were not safer you still would have to wear one. It's a cruel world sometimes.

Yes and no. I accept in a sense that I won't bang my head against their rules or try to start a revolution in diving industry; I do not accept in a sense that I see no reason why I should hide my disaproval of such rules. I certaily will use my bucks elsewhere, as so many of them kindly suggested. This world is certainly cruel, and it is cruel both ways.

But what you really intended to do was to ask a rhetorical question. That is a question that you really never wanted an answer to but rather just asked as a method of espousing your own viewpoint. Your viewpoint is that there is not enough evidence to justify boat operators to require divers to wear computers for the reason of increasing safety.

Dale, why don't you stop trying to read inside my brains? Rhetorical question needs no answer, so why bother asking? It just looks rhetorical to you since I expressed my viewpoint at the same time. "Not enough evidence" is not my viewpoint, it is a fact of life. I had my doubts, but now you guys convinced me.