Ratio Deco

[tursiops]

Man, that is seriously scary.

 

[decompression]

I get that, but other than anecdotal cases, what documented incidents have occurred? With any ratio deco? I learned ratio deco in 2005 and it was the be all end all of that time. I like to and learn from the feedback.


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---------- Post added July 22nd, 2015 at 07:13 PM ----------

GUE's ratio deco mimics the output from buhlmann 20/85 or VPM+2. If the ratio does not equal (within a few minutes, lets be pragmatic here) deco planner's output, the ratio is wrong.

An example is 21/35 at 150' with 50% as deco gas as "1:1". Through a range of times around 30mins, its pretty darn good. But at 45mins of BT the ratio is off by 15mins (buhlmann) or 7mins (VPM+2).

Well what to do?

You can ignore the algorithm and just do your ratio deco (even though according to the decompression software its not enough time) or abandon the ratio method and do the extra time.

For short BTs and relatively light gas burdens, the difference in time might not result in DCS. But as your deco times get longer, your risk % goes up EVEN IF you hold the algorithm constraints constant. So now your risk is going up (just by virtue of having a longer prescribed deco schedule) AND you're cutting time because you want to hold on to some 'ratio'? That's no good.

Then there's the whole deep stops thing (which NEDU's study would suggest is a less-than-ideal strategy), the s-curve oxygen window thing (which is bunk), not adjusting for altitude (physics still applies), and now apparently you don't need surface intervals?

Its irresponsible to be teaching decompression in this manner.

I did ask, how did AG develop his?


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[PfcAJ]

I did ask, how did AG develop his?

Beats me.

It would appear that he pulled it all out of his ass.

 

[decompression]

GUE's ratio deco mimics the output from buhlmann 20/85 or VPM+2. If the ratio does not equal (within a few minutes, lets be pragmatic here) deco planner's output, the ratio is wrong.

An example is 21/35 at 150' with 50% as deco gas as "1:1". Through a range of times around 30mins, its pretty darn good. But at 45mins of BT the ratio is off by 15mins (buhlmann) or 7mins (VPM+2).

Well what to do?

You can ignore the algorithm and just do your ratio deco (even though according to the decompression software its not enough time) or abandon the ratio method and do the extra time.

For short BTs and relatively light gas burdens, the difference in time might not result in DCS. But as your deco times get longer, your risk % goes up EVEN IF you hold the algorithm constraints constant. So now your risk is going up (just by virtue of having a longer prescribed deco schedule) AND you're cutting time because you want to hold on to some 'ratio'? That's no good.

Then there's the whole deep stops thing (which NEDU's study would suggest is a less-than-ideal strategy), the s-curve oxygen window thing (which is bunk), not adjusting for altitude (physics still applies), and now apparently you don't need surface intervals?

Its irresponsible to be teaching decompression in this manner.

"You don't need surface intervals" is incorrect, the UTD mindeco accounts for SIT under and over an hour.


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---------- Post added July 22nd, 2015 at 07:19 PM ----------

Beats me.

It would appear that he pulled it all out of his ass.

Snappy, and what I had expected earlier but if I may, when someone doesn't answer your questions, I'm waiting.....I will accept a I don't know.


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[PfcAJ]

I would argue that what's printed on that little card is a gross oversimplification of surface intervals.

But AG does say at the 6:43 mark that RD doesn't have surface intervals. I'll give him the benefit of the doubt and go with your card for the sake of argument.

If you think you can dive repetitively with just 1hr surface intervals and no adjustment to your ascent plan/bottom time, you're gunna have a bad time.

---------- Post added July 22nd, 2015 at 11:26 PM ----------

Snappy, and what I had expected earlier but if I may, when someone doesn't answer your questions, I'm waiting.....I will accept a I don't know.

Well he's not basing it on deco algorithms (as we've established).

Ergo...

 

[PfcAJ]

Also here's some fun deco stuff for the interested reader

http://archive.rubicon-foundation.o...33/2009_UHMS_Risk_poster_final.pdf?sequence=1

 

[decompression]

This seems pretty legit.......
http://s1cdn.joomag.com/pdf/0/29/29...UTD Journal Volume 2, Issue 11, November 2014

A five year study with doctors and scientists........


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[decompression]

I would argue that what's printed on that little card is a gross oversimplification of surface intervals.

But AG does say at the 6:43 mark that RD doesn't have surface intervals. I'll give him the benefit of the doubt and go with your card for the sake of argument.

If you think you can dive repetitively with just 1hr surface intervals and no adjustment to your ascent plan/bottom time, you're gunna have a bad time.

---------- Post added July 22nd, 2015 at 11:26 PM ----------



Well he's not basing it on deco algorithms (as we've established).

Ergo...

The card is mindeco......not ratio deco.

It seems that I end up "defending" UTD and the usual suspects are very quick to jump on anything with those initials. I ask if there is something political based in the history between the DIR agencies and certain peoples position within the original agency please pm me. I do post often but that it what I'm most familiar with and I think others have been scared to even mention UTD. I genuinely do not have a dog in the fight regardless of my credentials but I'm open to actual fact based arguments or opposing view points.

It looks as though he is using Buhlman.......contrary to your statement of no algorithm. Seriously, familiarize yourself the facts and present a contrary opinion. I believe your opinions are genuinely valuable and I'm interested in what you have to say.


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[PfcAJ]

There's LITERALLY no published data, I have no idea what "blood cell dust" is.

This isn't science...

---------- Post added July 22nd, 2015 at 11:46 PM ----------

The card is mindeco......not ratio deco.

It seems that I end up "defending" UTD and the usual suspects are very quick to jump on anything with those initials. I ask if there is something political based in the history between the DIR agencies and certain peoples position within the original agency please pm me. I do post often but that it what I'm most familiar with and I think others have been scared to even mention UTD. I genuinely do not have a dog in the fight regardless of my credentials but I'm open to actual fact based arguments or opposing view points.


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The card is still wrong. My argument is that the strategies AG is teaching are baloney.

I don't care one way or another in the initials war when it comes to deco. I was a pretty pro-deep stops guy, then science came out that swayed my opinion. Same with o2 window.

 

[decompression]

The card is wrong, rd is baloney....can you offer why?

To my other question....how did GUE develop/prove RD?


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