Ratio Deco

[PfcAJ]

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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I just went through both of those things. If you're not going to take the time to read my posts I'm not going to continue.

On RD, MD, and not being concerned with surface time: http://www.scubaboard.com/forums/ad...10982-ratio-deco-post7459661.html#post7459661

On GUE's version of RD: http://www.scubaboard.com/forums/ad...10982-ratio-deco-post7459863.html#post7459863

---------- Post added July 23rd, 2015 at 12:04 AM ----------

We've already established that deco risk % increases as deco time increases (see rubicon link I posted).

If you're going to be cutting deco time on longer dives (which is what AG's ratio deco does relative to the popular algorithms) your risk goes up even more.

Its pretty elementary. Not enough deco time = bent. Less deco time = increased change of bent.

 

[Adobo]

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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I guess my struggle is, even after reading the back and forth in this thread and reading the referenced material and watching Andrew's intro video, I still don't understand how Andrew came to the conclusion that this "strategy" is appropriate for a wide audience.

I mean, I get the 1:1 rule when diving 21/35 to 150ft and using 50% as your deco gas. But I get that because I get very similar results when I model the dive in deco planner. So basically, I am not relying on ratio deco as much as I am relying on Buhlmann. I am just using ratio deco to remember what deco planner spits out (or an approximation of it).

My confusion here is, what happens when Andrew's ratio deco diverges from models that have data across a broader audience? I mean, Andrew is like 6'5" and very fit. I am 5'7" and I carry a few extra lbs. He participates in triathlons. I run on a treadmill. He must be tight on his stops. I am, at times, kind of sloppy.

Andrew not getting bent using his strategy over the course of a thousand dives is not quite the same thing as a wider cross section of people not getting bent using his strategy.

I'm not saying that Ratio Deco doesn't have science and math behind it. I am simply asking, what is the science and math behind it?

Disclaimer: I don't care much about the initials. I just like diving.

 

[WhiteSands]

For AG, what has he done to develop/prove etc, his version of ratio deco? How does it differ from any other versions of ratio deco? How did they develop/prove their version?
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I'm curious to know the answer to your question. What has AG done to prove/develop his version of ratio deco? I know he did some stuff with some divers and scientists in Italy and I think he concluded that UTD's ratio deco was better than Buhlmann GF (I think the GF they tested against was 30/85, but I can't be certain) but that was pretty recent (after UTD's version of ratio deco had already been taught to many people). I have never seen the peer reviewed and published white paper on this research though.

I am curious to know what kind of verification or testing was done prior to it being taught in UTD classes?

Would also appreciate an answer to my previous questions on UTD's teaching which apparently seems to contradict the widely used NOAA air dive tables, if you do choose to answer.

Thank you.

 

[Adobo]

Oops.. sorry. Double post.

 

[PfcAJ]

My confusion here is, what happens when Andrew's ratio deco diverges from models that have data across a broader audience? I mean, Andrew is like 6'5" and very fit. I am 5'7" and I carry a few extra lbs. He participates in triathlons. I run on a treadmill. He must be tight on his stops. I am, at times, kind of sloppy.

Andrew not getting bent using his strategy over the course of a thousand dives is not quite the same thing as a wider cross section of people not getting bent using his strategy.

I think this is probably important. Some folks (for reasons that are poorly understood) are less susceptible to DCS. Fitness is a thing, but there are other factors like pulmonary shunts, immune response, and a bunch of other stuff.

 

[decompression]

Sorry AJ, you haven't. Post 18, you don't know what AG based RD on ( which I posted later #37), tables are based on math. But RD is based on Buhlman. You say "people getting hurt", I asked who.....still waiting, or is it just speculation on your part. And once again, how did GUE develop RD? To you agree with GUE RD?


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---------- Post added July 22nd, 2015 at 08:40 PM ----------

I'm curious to know the answer to your question. What has AG done to prove/develop his version of ratio deco? I know he did some stuff with some divers and scientists in Italy and I think he concluded that UTD's ratio deco was better than Buhlmann GF (I think the GF they tested against was 30/85, but I can't be certain) but that was pretty recent (after UTD's version of ratio deco had already been taught to many people). I have never seen the peer reviewed and published white paper on this research though.

I am curious to know what kind of verification or testing was done prior to it being taught in UTD classes?

Would also appreciate an answer to my previous questions on UTD's teaching which apparently seems to contradict the widely used NOAA air dive tables, if you do choose to answer.



Thank you.

I assume questions for me,

I believe AG got the idea from when he was the training director at GUE. I'm unsure of practical testing other than adoptions by the certified divers from the agency. More of a question for AG. The study, posted #18, is the first that I'm aware of that had that kind of scientific and medical support.

Which contradictory teaching are you wondering about?


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---------- Post added July 22nd, 2015 at 08:46 PM ----------

I think this is probably important. Some folks (for reasons that are poorly understood) are less susceptible to DCS. Fitness is a thing, but there are other factors like pulmonary shunts, immune response, and a bunch of other stuff.

Totally agree with that. I think that's a key that AG stresses that there is more control in RD to address these issues. I also see the benefits of deco planner and the others that you can choose the model, add deep stops, adjust GF's.


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[PfcAJ]

Sorry AJ, you haven't. Post 18, you don't know what AG based RD on ( which I posted later #37), tables based on math. But RD is based on Buhlman. You say "people getting hurt", I asked who.....still waiting, or is it just speculation on your part. And once again, how did GUE develop RD? To you agree with GUE RD?


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You just posted a link to a video that went on and on about how AG's Ratio Deco is different from buhlmann, then you want to tell me that its based on buhlmann? What about when it doesn't line up with Buhlmann? What do you do? I discussed the two choices (stick with your ratio or abandon it and go with the algorithm). Furthermore, its been said time and time again on this board and others that UTD's class doesn't even cover used of decompression algorithms.

GUE's ratio is just a trick that mimics's an algorithm's output and they spend a decent bit of time discussing the limits of applying a ratio method. You're still diving the algorithm, you're just using a handy ratio to get there. This is in contrast with UTDs version which has no algorithm. Critical difference. If GUE suddenly advocated something that was not inline with an algorithm I wouldn't be behind it at ALL.

You've then had posters come on here with their accounts of getting bent or seeing others getting bent using AG's methods.

Tell me, what do YOU DO if your ratio deco method falls outside of what buhlmann (or even vpm) puts out for a deco schedule?

I don't know if you haven't really experimented with putting different bottom times into the buhlmann algorithm, but the ascent times not perfectly linear across different times (as I showed before). You're trying to fit a straight line to a curve, and you can't really do that across a wide range of times.

 

[decompression]

I think the articles give a good background and the science around RD, you did read it and not just watch the video, right? I'll try to dig up more of the study, based on Buhlman, incorporates S curves and more details. I believe there is a chart that shows the variance between Buhlman and RD. Yes, John mentioned 6 of his group, I recall that long post awhile ago that, as I've asked you before, couldn't be solely attributed to RD. So, for the forth time, you say it's dangerous, it hurts people.....proof? You still haven't answered where GUE has developed and proved RD? Is it impossible for you to say you don't know something. I don't know how GUE did, I don't know where AG got his idea.

Where has it been said that RD doesn't cover decompression algorithms? Again, you are under the misconception that there is no algorithm.
Also, you say "posters", no, one poster, John, and again that was a long post and again it's anecdotal. Still waiting for your "LITERALLY" published data of accidents attributable to RD.

I don't necessarily want do defend UTD's RD against contrary views, in fact I want to see those opinions to increase my knowledge base but I do want people to understand there is something called Ratio Deco and the views regarding it should be more than "it's baloney".


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[WhiteSands]

I assume questions for me,

Which contradictory teaching are you wondering about?

Thanks for the reply. My question is in Post #7.

 

[Adobo]

I don't really know how much better (or that it is even better) Min-Deco is compared to doing safety stops at 3 mins at 5m. If we calculate total safety or "deco" stop time for min-deco (assuming a dive to 30m), 1min at 15m + 1min at 12m + 1min at 9m + 1min at 6m + 1min at 3m = total 5min of safety or "deco" stop time.

PADI and other recreational agencies teach divers to do a 3mins stop at 5m, so essentially min-deco has just 2min extra deco time compared to the traditional safety stop.

It seems a bit far-fetched to me that doing 2 min of extra safety stop time will magically make you "clean" whereas if we follow the NOAA (PADI) tables we end up in pressure group "O", with a lot of residual Nitrogen in our bloodstream.

Plus at the back of my mind, I am thinking of the NEDU study which basically says if you have to choose where to do your stops given a limited amount of time, it's probably better to do it shallow. This, suggests to me, that perhaps the recreation style safety stop of 3min at 5min might result in better off-gassing then min-deco.

But putting that aside, it seems pretty far fetched, even if we do assume doing the "deep" stops has some marginal benefit, that it will make you clean after 1 hour of SI, don't you think?

Also, I think maybe the comparison should be as follows:

In the "conventional" ascent, it is recommended to ascend no faster than ~33ft/min. So to get from 50ft to 15ft would take ~1 minute.

If it is true that you begin offgassing at 1/2 avg depth (or max depth, depending on where ascent is beginning), then it means that as soon as you hit 50ft, you are offgassing. The time you are traveling to 15ft (1 minute) could conceivably be considered as deco.

So it seems that the comparison should be ~4 minutes of deco for the conventional ascent vs 5 minutes of deco for min deco based ascent.​

By the way, I am not sure where this idea of "being clean" if you do an min deco ascent comes from. I think the pictures of UTD cards indicate that if you don't do a proper surface interval, you are meant to add deco time (increase from one minute to two minute stops) in the 30, 20 and 10 ft stops. I imagine this is to account for residual gas loads from previous dives. It would be interesting to see if this strategy is prescribed for 3/4/5 dives per day over the course of a weeks worth of diving.