DIR- GUE GUE standard for gradient factors?

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MolaSquared

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Does GUE have a standard for GF? I don't recall learning about that in Fundamentals.
 

CptTightPants21

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Does GUE have a standard for GF? I don't recall learning about that in Fundamentals.
20/85.

However it is more of an outdated relic sustained by inertia and bureaucracy.

The research done over the past few years has shown that it is sub-optimal and very few GUE divers use it any more. Even most of the instructors no longer use it in their diving which is why you may not have learned about it in Fundamentals.

Although it is more of a Tech 1 subject and fundies mentioned 20/85 and explained that that is where min-deco methodology was derived from.
 

Ouvea

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Wasn't a topic of discussion when I passed fundies many years ago. Deco Planner is set to 20/85. Up to you to decide.

We were taught to ascend to 50% of current depth at 30ft/minute. From that depth it's 10ft/minute to the surface. Would love to see the current literature for Fundamentals and see how it has changed since I completed the course nearly 10 years ago.
 

happy-diver

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Should ask Trace Malin how ratio deco went for him
 

rjack321

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Does GUE have a standard for GF? I don't recall learning about that in Fundamentals.
Because GFs (esp the low) don't really apply to no deco diving. In T1 you'll be using 20/85 in decoplanner.
 

boulderjohn

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Wasn't a topic of discussion when I passed fundies many years ago. Deco Planner is set to 20/85. Up to you to decide.

We were taught to ascend to 50% of current depth at 30ft/minute. From that depth it's 10ft/minute to the surface. Would love to see the current literature for Fundamentals and see how it has changed since I completed the course nearly 10 years ago.
After writing an article on deep stops in decompression diving, I attempted to do the same for recreational diving. In my research, I contacted GUE headquarters for an explanation of the theory behind Min Deco, and I got an official explanation. From reading many threads over the years, I suspect the official explanation will be news to many GUE divers.

Here are some key facts about it.
  • It has nothing to do with GFs and the changing thinking on deep stops.
  • It has nothing to do with deep stops at all, whether in NDL or decompression diving.
  • The primary reason for it as related to decompression theory is a belief that the ascent rate should be slower as you get near the surface. That is the only aspect of this related to decompression theory.
  • Halfway to the surface was chosen because anyone should be capable of the math required to compute half.
  • The stops from halfway to the surface have two purposes:
    • Slows the ascent, in accordance to the theory mentioned above.
    • It mimics the decompression ascent, thereby providing a consistent standard procedure for ascents for all dives.
 

CAPTAIN SINBAD

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After writing an article on deep stops in decompression diving, I attempted to do the same for recreational diving. In my research, I contacted GUE headquarters for an explanation of the theory behind Min Deco, and I got an official explanation. From reading many threads over the years, I suspect the official explanation will be news to many GUE divers.

Here are some key facts about it.
  • It has nothing to do with GFs and the changing thinking on deep stops.
  • It has nothing to do with deep stops at all, whether in NDL or decompression diving.
  • The primary reason for it as related to decompression theory is a belief that the ascent rate should be slower as you get near the surface. That is the only aspect of this related to decompression theory.
  • Halfway to the surface was chosen because anyone should be capable of the math required to compute half.
  • The stops from halfway to the surface have two purposes:
    • Slows the ascent, in accordance to the theory mentioned above.
    • It mimics the decompression ascent, thereby providing a consistent standard procedure for ascents for all dives.

Hi John, Mark Powell in Min-Deco quotes a study (I believe it was by DAN) where they tested half stops in recreational diving and how they resulted in better bubble scores than those who were extending one shallow stops that most computers would generate. I personally reached out to Mark Powell about these half stops. Here is the conversation:

Me: Greeting Mark, quick question. I understand your earlier version of Deco for Divers that doing half stop in recreational diving profiles (100 ft and shallower) can be beneficial. With Spisni study on deep stops and US Navy study, do you still regard it to be a good decompression practice? It would require a GF lo to be 5. Thanks.

Mark Powell: Hi Aziz, those studies were not on no-stop dives so i wouldnt say they were relevant. I think the DAN study is still relevant for no stop dives so I would still do them on no stop dives.


The man is really high up in TDI food chain and as far removed from DIR as they come.
 

boulderjohn

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Hi John, Mark Powell in Min-Deco quotes a study (I believe it was by DAN) where they tested half stops in recreational diving and how they resulted in better bubble scores than those who were extending one shallow stops that most computers would generate. I personally reached out to Mark Powell about these half stops. Here is the conversation:

Me: Greeting Mark, quick question. I understand your earlier version of Deco for Divers that doing half stop in recreational diving profiles (100 ft and shallower) can be beneficial. With Spisni study on deep stops and US Navy study, do you still regard it to be a good decompression practice? It would require a GF lo to be 5. Thanks.

Mark Powell: Hi Aziz, those studies were not on no-stop dives so i wouldnt say they were relevant. I think the DAN study is still relevant for no stop dives so I would still do them on no stop dives.


The man is really high up in TDI food chain and as far removed from DIR as they come.
I am familiar with this, and it is interesting. There are two studies conducted 15-20 years ago regarding deep stops on recreational dives, and both are considered to be flawed. Partly because of that, DAN America's does not recommend deep stops for NDL dives. Despite that, DAN Europe does recommend deep stops, based on those two studies that are considered to be flawed.

Mark was a very late and very reluctant convert away from deep stops on decompression dives, and he still isn't sure. He has conducted a couple of recent studies that do not rise to the level of publishable scientific research, and they are at best inconclusive. I read them as supporting shallower stops. He did something very innovative and fascinating in that he measured venous gas emboli (VGE) after dives and found the scores of deeper stop divers similar to shallower stop divers. But he continued to measure them over time and found a significant difference in that the shallower stop divers had bubble scores drop rapidly while deeper stop divers stayed high. IIRC, in some case they even rose initially.

My original intent was to write an article on deep stops in recreational dives, and I finally decided that I could not do so because the research was simply not there to say anything one way or the other. The standard approach of an ascent at a safe rate with safety stops on some dives has more than 100 years of research behind it showing it to be pretty darn safe. There is no good research showing any advantage to any other ascent profile that I know of.

If you think about it, such research getting definitive results would be truly daunting, and since the traditional approach works so well, there is no real push to improve it.

Think about this--the following ascent profiles are all considered to be acceptable for NDL diving, whether you are using tables or computers. (To stop the tables argument, the ascent rates are "no faster than" in nature.) The track record on all of them is pretty good. Would you include all of them in a study to see what works best?
  • Ascend at 60 FPM and do a safety stop on deeper, longer dives.
  • Ascend at 30 FPM and do a safety stop on deeper, longer dives.
  • GUE Min deco ascent.
  • Ascend at 30 FPM and do a safety stop at half depth and another at 15 feet.
  • Ascend at 30 FPM until coming to an interesting section of reef at 40 feet and then spend 20 minutes there before going up to 20 feet and spending 20 minutes there, too (multi-level dive).
  • Begin ascent along the reef at a few minutes short of NDL and then work your way shallower, riding the computer to keep a few minutes away from NDL until you finally reach 15 feet for a safety stop.
 

boulderjohn

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Me: Greeting Mark, quick question. I understand your earlier version of Deco for Divers that doing half stop in recreational diving profiles (100 ft and shallower) can be beneficial. With Spisni study on deep stops and US Navy study, do you still regard it to be a good decompression practice? It would require a GF lo to be 5. Thanks.

Mark Powell: Hi Aziz, those studies were not on no-stop dives so i wouldnt say they were relevant. I think the DAN study is still relevant for no stop dives so I would still do them on no stop dives.
I did not mention this before, but Mark is absolutely correct in saying that there is a difference between decompression dives and no-stop dives. If there is anything I learned in my research, it is that there very much is such a difference, with a small gray area in between.

No-Stop: If you begin your ascent within NDLs, always use a safe ascent rate, and stay within DNLs during the ascent, it doesn't seem to matter how long very much how long it takes for that ascent. People doing multi-level dives will regularly dive below 100 feet to see something and then do an ascent with lingering stops at different depths for a total run time of 80 minutes or so, and there is no known evidence that this is harmful. You should always be able to go directly to the surface at any point in that dive without serious risk of decompression sickness.

Decompression Diving: Once you are clearly in need of required decompression, your ascent rate and the depth and time of stops matters a great deal. Lingering at depth will create a demand for increased decompression time in shallower water. A direct ascent to the surface brings a serious risk of decompression sickness.

Gray Area: Near the deepest, longest edge of NDL diving and that the beginning stages of decompression diving is a gray area where the risk of decompression sickness on an NDL dive with a direct ascent increases to the point where safety stops become important and begin to cross the line into decompression stops. That gray area also includes decompression diving with short, shallow stops where the risk of DCS in the case of a missed stop is not so great.
 
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