Decompression Modeling

[gsk3]

See Tim, now you'll have to take Tech1 with me instead of Rec3, so you get all the theory and tweaks in

Lynne- as usual it is as though you read my mind, or more likely I read your infinitely wiser one

Liuk- thanks for the info. I'd been playing with V-Planner over the past few days to try to get a more practical sense of how the theory plays out, and didn't know what conservatism setting was used in the real world.

And Ranier- totally reasonable not to post the profile. Tim's not about to run out and do anything unwise, though. As far as I can tell he's as cautious as I am, and from what I've read of Lynne's we share similar sensibilities. No uncertified deco dives in our future. I think we're both just the type that likes having an understanding of the theory way beyond what we'll actually use. Again, professional hazard.

Best,
Ari

 

[ScubaFeenD]

No uncertified deco dives in our future. I think we're both just the type that likes having an understanding of the theory way beyond what we'll actually use. Again, professional hazard.

Yeah, an understanding that is beyond my current skill level for sure. It is still fun to learn more about it though.

Well put, Ari.

PS: Tech1 will be happening ASAP, no doubt.

 

[Peter Guy]

Reading threads like this always make me smile. It is ALL "FrankenDeco" as far as I can tell.

I especially get a kick out of the "I don't use no stinkin' computer" people -- who then "tweak" their computer generated deco schedule to make it "fit" something they think they believe they understand about someone's theory which hasn't been tested or validated very much.

Perhaps it really does come down to -- "If you do the crime (deco) you must do the time" and how you do the time isn't as important as just doing it somewhere.

 

[gsk3]

Reading threads like this always make me smile. It is ALL "FrankenDeco" as far as I can tell.

I especially get a kick out of the "I don't use no stinkin' computer" people -- who then "tweak" their computer generated deco schedule to make it "fit" something they think they believe they understand about someone's theory which hasn't been tested or validated very much.

My limited understanding is that the tweaking comes down to another interesting but un-proven proposition, namely that experience of "sub-clinical" DCS is predictive of risk of true DCS. Therefore, if you do a dive and are exhausted afterwards in the absence of substantial physical activity, you start making your curves more conservative. This seems to be the basis for Pyle's deep stops as I understand it...he was fishing and paused to let the swim bladder depressurize, and then he felt better afterwards.

 

[liuk3]

I think that Peter says it best in implying that it's all a bit random in some sense. There's no guarantees that you won't get hurt whatever your profile, so proceed at your own risk if you decide to do this type of diving. I would certainly highly recommend taking a technical dive class from a reputable instructor rather than Internet learning. It's good that Rainer's post reminds us of that.

 

[Rainer]

Each individual has to take their own responsibility for how they want to execute or modify their own decompression profiles.

While I think this has to (also) be a team decision, ultimately, liuk3 is correct. The consequences of "bad" deco affect the diver making those choices. Proceed slowly (depth, BT) and keep track off how you feel after dives. Adjust deco if you're not feeling well. Remember, most of us are doing this for recreation. The goal is always to come home healthy to loved ones.

 

[gsk3]

It's definitely random, but being in a statistical field I tend to have a different view on what that word means than most. Drawing straws is random, but you at least know what the odds of coming up short are. This is worse than that-- not only are you subject to the vagaries of fate or fluctuations of the universe on a scale we cannot comprehend, but you don't even know the odds, because the underlying distribution is fundamentally unknown or unparameterized.

Again, neither Tim nor I is stupid enough to incur a deco obligation without proper training. But Ranier is wise to not post details, because a) he doesn't know us, and b) other people can read this post.

That said, I seem to make it out to LA once every year or so these days, so perhaps we can work on a) ;-). Will have to do better than my attempt to make it out to Seattle (sorry Lynne!).

Best,
Ari

 

[jjones9527]

I especially get a kick out of the "I don't use no stinkin' computer" people -- who then "tweak" their computer generated deco schedule to make it "fit" something they think they believe they understand about someone's theory which hasn't been tested or validated very much.

I think the no computer issues comes down more to having some semblance of a plan before hand, rather than just having the computer make it up as you go along. Too many people rely solely on what their computer tells them, and haven't a clue what to do when it fails mid dive.

 

[TSandM]

the underlying distribution is fundamentally unknown or unparameterized.

I believe to some degree, the distribution is known -- I think there are definitely depth/time combinations where you can say pretty much for sure that if you do them, you will be symptomatic. And there are some where, within 99% probability, you won't be. The problem is that we are trying to define in fine a process which is only understood probabilistically, and that type of understanding is poor at defining probabilities for any individual.

It's like coronary risk factors. They're great at predicting cardiac risk likelihood in a population, and all but worthless for assessing it in individuals.

 

[lamont]

I actually disagree with this. I think it's significantly easier to add stops and otherwise modify the schedule in DP than VP. Only issue is that DP won't run on my (native) Mac, so I now turn only to VP when needing to check software. Oh, well...

DP runs under crossover, without having to pay bill gates:

Windows Applications Seamlessly Integrated on Mac OS X - Mac Windows - CodeWeavers