Deep Stops Increases DCS

[Patoux01]

In RD terms, for this depth: 100/100 & VPM-B = 4:1, GF = 6:1

Clearly the GF plan is grown to ridiculous amounts. Why is that?

What if it was VPM that got ridiculously low on the amount of deco it gives?

 

[rossh]

Hi,

All deco plans and models, incur increasing risk as they get deeper and longer (including pDCS measures). Its the nature of the task. You cannot avoid this. David made a point of saying this at the TekUSA presentation. Showed numerous graphs demonstrating this point.

So your hope for a uniform risk, is moot.

As to which one (real model vs GF patch) is wrong and gets out of sync? RD has some interesting insights that allow for measuring profiles. The ratio part is a handy way to cross compare. In this respect RD and real ZHL and VPM and RGBM and others, all loosely match up. While your x/70 takes off for the stars, and adds enormous amounts of excess shallow deco. Its GF x/70 vs the rest.

GF is powerful, and you can make virtually any profile you want with it. But with such wide ranging abilities, one also needs to appreciate when its gone too far. These x/70 with larger deco profiles is clearly one of those places.

But if your desire is to be seek out any justification of these extra long and unnecessary and exaggerated shallow stop times, then I guess GF must be a perfect fit for this delusion.

Its not 'out of sync' with anything. VPM+3 just doesn't provide enough deco time. I already posted links regarding the non-linearity of risk in regards to longer deco times. If you want to assume more risk, do a shorter time. If you want to assume more risk, spend less time on deco gases. If you want to assume more risk, do less time on oxygen. AKA all the things that VPM wants you to do.

RD has nothing to do with it. At all. But in terms of understanding your decompression requirements, it highlights just how short VPM is.

I don't think any algorithm is 'correct', nor do I 'love' any algorithm. I do think some are better than others, and I think GF is better than VPM so reasons I've stated over and over (as have others). They're all wrong. GF might just be less wrong.

 

[PfcAJ]

Hi,

All deco plans and models, incur increasing risk as they get deeper and longer (including pDCS measures). Its the nature of the task. You cannot avoid this.

So are you trying to say that a probabilistic model that outputs a schedule with a 2% risk for a short dive is unable to produce a schedule with a 2% risk on a long dive?

Or are you saying that attaining the same risk probability across a range of depths and times is impossible?

Think that through for a bit before you reply.

 

[Jax]

So are you trying to say that a probabilistic model that outputs a schedule with a 2% risk for a short dive is unable to produce a schedule with a 2% risk on a long dive?

Or are you saying that attaining the same risk probability across a range of depths and times is impossible?

Think that through for a bit before you reply.

Actually, that is what I am reading these days, AJ. The longer the dive, the more the model needs tweaking.

I am looking for the specific discussion - It is in relation to the development of the VPM-B/E because of the difference in > 1 hour deco times.

 

[PfcAJ]

Actually, that is what I am reading these days, AJ. The longer the dive, the more the model needs tweaking.

I am looking for the specific discussion - It is in relation to the development of the VPM-B/E because of the difference in > 1 hour deco times.

None of the popular models are probabilistic.

If they were we wouldn't be having this conversation.

 

[Jax]

I would have said all the models are probabilistic.

The aim of a probabilistic logic (also probability logic and probabilistic reasoning) is to combine the capacity of probability theory to handle uncertainty with the capacity of deductive logic to exploit structure of formal argument.

We really don't have a model that covers all of it.

 

[PfcAJ]

None of the popular models are probabilistic.

I would have said all the models are probabilistic.

The aim of a probabilistic logic (also probability logic and probabilistic reasoning) is to combine the capacity of probability theory to handle uncertainty with the capacity of deductive logic to exploit structure of formal argument.

We really don't have a model that covers all of it.

negative.

None of the models (Vpm, rgbm, buhlmann) tell you the risk (probability of dcs) for the outputted ascent profile.

 

[KevinNM]

None of the models (Vpm, rgbm, buhlmann) tell you the risk (probability of dcs) for the outputted ascent profile.

My impression is the pretty much the only approach that provides probability data are the tables from the various navies. Which are mostly not model based and have obvious issues for non-commercial diving. Are there other options that have enough human research behind them?

 

[PfcAJ]

My impression is the pretty much the only approach that provides probability data are the tables from the various navies. Which are mostly not model based and have obvious issues for non-commercial diving. Are there other options that have enough human research behind them?

Not that are readily available, unfortunately.

 

[lv2dive]

A. I'm not sure why you keep bringing ratio deco into the conversation, to my knowledge no one has mentioned it in this latest go-around except maybe Kevin. Why throw it in when it is not what the conversation is about?

B. A reasonable amount of well-respected people are doing exploration-level diving (and by that I mean minimum of four hours of deco, not 60-120 min of deco) with a GF high of 70. So to say "it's gone too far" is inappropriate IMHO. (See "But with such wide ranging abilities, one also needs to appreciate when its gone too far. These x/70 with larger deco profiles is clearly one of those places" below.)

Personally I know what works for me, and moved away from a GF high of 70 a while ago - but that doesn't make it *wrong* or a model that has gone too far.

Hi,

All deco plans and models, incur increasing risk as they get deeper and longer (including pDCS measures). Its the nature of the task. You cannot avoid this. David made a point of saying this at the TekUSA presentation. Showed numerous graphs demonstrating this point.

So your hope for a uniform risk, is moot.

As to which one (real model vs GF patch) is wrong and gets out of sync? RD has some interesting insights that allow for measuring profiles. The ratio part is a handy way to cross compare. In this respect RD and real ZHL and VPM and RGBM and others, all loosely match up. While your x/70 takes off for the stars, and adds enormous amounts of excess shallow deco. Its GF x/70 vs the rest.

GF is powerful, and you can make virtually any profile you want with it. But with such wide ranging abilities, one also needs to appreciate when its gone too far. These x/70 with larger deco profiles is clearly one of those places.

But if your desire is to be seek out any justification of these extra long and unnecessary and exaggerated shallow stop times, then I guess GF must be a perfect fit for this delusion.