GUE training and deep diving

[CptTightPants21]

Great, Ken!

I have asked countless times for the decompression theory behind minimum deco, and I have not gotten an answer. The last time I asked it, I was definitely told that there was no actual decompression theory behind it, but it was instead a training exercise to enable the diver to practice dong decompression stops during an NDL ascent. I find that hard to believe, but I have had no better answer.

Yeah, I would say it is part training exercise to have divers practicing stops and part gradual ascent profile for NDL--not really deco in the strict sense of the word

If you take a recreational dive from 100ft (30m)
1. Non GUE would ascend from 100ft to 15ft and do a 3 min safety stop - depending on ascent rate that ascent would be 6-7min
2. GUE - Min Deco ascent would be 7 min. Ascending to 50ft and then slowing ascending 10ft a minute.

Just as many organizations, GUE needed to make certain things their own. Even though it accomplishes the same goal as any other NDL profile ascent, it is different enough that it needs it own name, hence min deco was born.

 

[boulderjohn]

It's the NOAA dive tables.

Please explain. I have never heard that approach was part of the NOAA's practice.

 

[boulderjohn]

Yeah, I would say it is part training exercise to have divers practicing stops and part gradual ascent profile for NDL--not really deco in the strict sense of the word

If you take a recreational dive from 100ft (30m)
1. Non GUE would ascend from 100ft to 15ft and do a 3 min safety stop - depending on ascent rate that ascent would be 6-7min
2. GUE - Min Deco ascent would be 7 min. Ascending to 50ft and then slowing ascending 10ft a minute.

Just as many organizations, GUE needed to make certain things their own. Even though it accomplishes the same goal as any other NDL profile ascent, it is different enough that it needs it own name, hence min deco was born.

What I am looking for is an explanation on the decompression theory behind that approach. It is a serious question. I just finished working on an article on current thinking behind decompression dive ascent strategies, and I am thinking of writing one for NDL ascent strategies as well. How does GUE know that its min deco ascent strategy is as good as or better than the strategies used by nearly everyone else?

 

[Lorenzoid]

. . .

The ascent profile is definitely a control exercise. Are you hitting your stops? Are holding them? Is the overall time taken for the ascent in line with what it should have been? Is the team together at each stop? If you need to do an air share during ascent do you still make the stops and times? If you can't do that reliably you won't get a tech pass and if you somehow slip through I've been assured that tech 1 will not be any fun.

Yes, and it's nice that GUE encourages every diver to turn every dive into an opportunity to practice and improve, but for those divers who steadfastly wish to remain no-stop divers, why would this sort of exercise be useful? It does seem pointless for those (presently a minority in GUE, but who knows what the future of GUE may hold) divers who have no interest in learning to plan deco dives.

 

[lv2dive]

I disagree strongly. I am speaking from the following experience/ knowledge:

• 10 years of diving experience before I took fundies (8-9 years since then)
• GUE Cave 2/Tech 2 diver
• Someone who Failed (not provisionally passed) their first fundies class (which btw was the subject of a thread with over 400 posts on ScubaBoard before it was shut down)
• Someone who went outside of GUE for training during and after my progression to Cave2/Tech 2, including but not limited to basic training on three CCR units, CCR Cave and MOD3 (hypoxic trimic fot CCR)

First of all, I’m going to start out by saying that in my experience, some of the very best students are the new divers- They have not had time to develop bad habits that are going to have to be broken. Personally I had to unlearn 10 years / a couple hundred dives of poor recreational diving techniques.

Secondly, one can not accurately describe or understand fundies unless they have taken it. I find it extremely amusing how people who have not taken fundies feel like they are experts on what the class is about. One clue: the equipment, which everyone who hasn’t taken the class obsesses about, is a small part of the class - much more time/energy is spent on learning to dive as a team.

While I did fail my first class, I was interested enough to go back and retake it with a different instructor. It is one of the most challenging, if not the most challenging classes, that most people will ever take. While my first fundies class was not worth the total amount of money I spent on tuition and expenses, the re-take of the class was the best diving dollars I have ever invested (except maybe for my first Shearwater ) Regardless of where they are in their diving - whether they are almost brand new open water diver‘s or instructor trainers for other agencies, I don’t know a single person (except from my CF of a class) who hasn’t felt like the class was worth it.

There may be some historical precedent with certain instructors that fundies is more of an evaluation than a learning opportunity - I felt that way about my first class. In all fairness, many others have taken classes with the instructor from my first class, and had a great experience, and there were logistical issues that played into some of the problems with that class (6 students + 1 student instructor/ intern, location problems). The main point being, the overwhelming majority of GUE instructors are passionate about teaching and helping their students become better divers. Again, speaking from experience, as someone who has taken classes with multiple instructors and used to videotape classes, i have seen a dedication to helping students work through their issues and improve their skills and enjoyment of diving. I am only aware of that “evaluation” mentality with one instructor and for all I know, they could be more instructive now.

 

[kierentec]

Great, Ken!

I have asked countless times for the decompression theory behind minimum deco, and I have not gotten an answer. The last time I asked it, I was definitely told that there was no actual decompression theory behind it, but it was instead a training exercise to enable the diver to practice doing decompression stops during an NDL ascent. I find that hard to believe, but I have had no better answer.

The decompression theory behind the ascent profile for MDL dives is simply the understanding that a controlled ascent to the surface if preferred over a direct and rapid ascent. For an MDL dive, the ascent time is about the same as an ascent straight to 15' and then conducting a 3 minute stop, the stop time is just distributed over several stops.

The answer that the MDL ascent is "just" a training exercise is not really accurate. However, the ascent strategy GUE applies to all dives is consistent from Rec 1 to Tech 2 and onward. It is simply a practical and consistent approach to ascending from a dive. Because the ascent profile is consistent, each time you ascend from any dive, you are essentially practicing.

 

[PfcAJ]

Great, Ken!

I have asked countless times for the decompression theory behind minimum deco, and I have not gotten an answer. The last time I asked it, I was definitely told that there was no actual decompression theory behind it, but it was instead a training exercise to enable the diver to practice doing decompression stops during an NDL ascent. I find that hard to believe, but I have had no better answer.

Ok I know the answer.

Its what deco planner spits out when the maximum stop times are 1min. That's it. Thats the minimum decompression limit. Any longer bottom time, and the stop times become greater than 1min.

The idea is to "do the min deco ascent" and you're good for all dives up to bottom times that surpass the min-deco limit.

Curiously, it just so happens to be about the same total length as a 3-5min safety stop, just spread out across multiple depths.

 

[kierentec]

What I am looking for is an explanation on the decompression theory behind that approach. It is a serious question. I just finished working on an article on current thinking behind decompression dive ascent strategies, and I am thinking of writing one for NDL ascent strategies as well. How does GUE know that its min deco ascent strategy is as good as or better than the strategies used by nearly everyone else?

They don't, and they don't claim to. Just like nobody "knows" that a 30/70 GF is "better" than a 90/100 or a 20/80. At the end of the day, there are so many variables, it is impossible to say for sure. However, we do know that the simpler and more consistent we keep procedures from the most benign dives to the most complex, the less opportunities we have for confusion and failures. This includes what many consider the most critical component of any dive, making our way back to the surface.

 

[Graeme Fraser]

If these numbers are correct, your SAC rate on the bottom was between .6 -.7 cuft a minute which is a great SAC rate for a new diver and right around the average for an experienced diver. What where the conditions like on the ascent that caused such an elevated breathing rate -- current? How long did it take you to ascend?

If you think that 25 min at 30m was too quick I think doubles and deco might be in your future.

I was thinking the same. In new money that's about 15-18 litres pm which is fine, particularly for a relatively new diver. Fixating on SAC will probably achieve the opposite to what you're looking for. More dives = better buoyancy control = more relaxed = lower SAC.

 

[CptTightPants21]

What I am looking for is an explanation on the decompression theory behind that approach. It is a serious question. I just finished working on an article on current thinking behind decompression dive ascent strategies, and I am thinking of writing one for NDL ascent strategies as well. How does GUE know that its min deco ascent strategy is as good as or better than the strategies used by nearly everyone else?

I am not sure we will every get the science behind it apart from that it works. The same goes for for the 3 min safety stop at 15ft. I am not 100% on the timeline, but when I was certified in 2001 the 3 minute safety stop was only a suggestion and now it is taught as mandatory. If anything recreational scuba has gotten closer to GUE in that regard. I think the no deco dives are benign enough and the total ascent times from all the methods so close to each other that there is no right answer. GUE likes a consistent approach and the fundamentals of their min deco ascent can be translated into every facet of advanced scuba.

Yes, and it's nice that GUE encourages every diver to turn every dive into an opportunity to practice and improve, but for those divers who steadfastly wish to remain no-stop divers, why would this sort of exercise be useful? It does seem pointless for those (presently a minority in GUE, but who knows what the future of GUE may hold) divers who have no interest in learning to plan deco dives.

It's a method of controlled ascent. It helps keep the group together and helps lay out a schedule and a benchmark that everyone can gauge--are we going to slow or two fast? Do we actually have control while ascending (the slow stops) or are we ascending slightly out of control but adjusting/compensating with air dumps and adds. As stated above, there is little difference between the total ascent times between the methods, but min deco has a consistent approach between rec and non-recreational diving.