Keeping up with Changing Thinking in Scuba

[MargaritaMike]

But I only know who he is because of Scuba Board!

I see this as a problem that many of us experience. We only know who someone is from SB or maybe somewhere else. Knowing who people are from SB is not as simple as it sounds. For instance, I go to great lengths to only expose who I am to a select few. Not that I'm hiding anything, but maybe....

Cheers -

 

[DevonDiver]

The trimix diving course I teach has a section imploring students to keep up with the changing research in the world of scuba.

The irony being that the manual has been neglected from any update since 2003?

 

[Centrals]

There are divers still believing reversed profile is BAD and to be avoided.
Some DC will also punish you with shorter ndl if you execute a reversed profile dive.

 

[Blasto]

There are divers still believing reversed profile is BAD and to be avoided.

It's not just a few loose divers. I've got first-hand experience with dive centers outright banning reverse profiling. It doesn't matter that they don't understand why - they've heard that some think it increases risk, and don't want even an impression of taking less than every possible precaution.

The reverse-profiling issue is a bit different from deep stops, though. While deep stops were based on a combination of anecdotal evidence (Pyle) with a sophisticated theory (RGBM), the belief in the danger of reverse profiles comes from not even trying to understand the issue in terms of established deco theory. Real issues with some reverse profiles and an oversimplified analogy with multi-level diving were enough.

 

[AfterDark]

It's not just a few loose divers. I've got first-hand experience with dive centers outright banning reverse profiling. It doesn't matter that they don't understand why - they've heard that some think it increases risk, and don't want even an impression of taking less than every possible precaution.

The reverse-profiling issue is a bit different from deep stops, though. While deep stops were based on a combination of anecdotal evidence (Pyle) with a sophisticated theory (RGBM), the belief in the danger of reverse profiles comes from not even trying to understand the issue in terms of established deco theory. Real issues with some reverse profiles and an oversimplified analogy with multi-level diving were enough.

Just to underline how absurd this reverse-profiling phobia is a; some issues compared to how many "undeserved" hits doing it the "right way"?

There was a thread on these types of irrational diving misconceptions a few months ago.

 

[RyanT]

@Eric Sedletzky, there was no unusual spike in DCS cases. Much of the change in thinking came about as a result of a controlled, experimental study done by the NEDU. In that study, they bent more divers who dove their "deep stop" profile. The effect was fairly small, but it suggested the effect was real

https://www.johnchatterton.com/wp-content/uploads/2013/03/NEDU_TR_2011-06.pdf

Following this study, Dr. Simon Mitchell, Doolette, and others did some modeling to suggest why the NEDU got the results they did.

 

[RyanT]

As for the original question, two other sources that haven't been mentioned are 1) the technical peer-reviewed literature and 2) Shearwater's site. I read these and pretty much anything else I can find.

 

[kelemvor]

The trimix diving course I teach has a section imploring students to keep up with the changing research in the world of scuba. You don't want to base critical diving decisions on ideas that have been repudiated and are no longer believed to be true. The course itself is in example for that. It has extensive information on putting deep stops into a dive profile, and the standards require students to plan and execute a dive using deep stops. That standard, however, was dropped from the course last year, because recent research does not support the use of deep stops. The course, then, set a good example for its students when it changed the standards in light of recent research.

So how does a scuba diver keep up with changes in scuba knowledge?

I imagine a number of you would immediately reference ScubaBoard--that is, after all, how you found this thread. If you are a ScubaBoard reader who has encountered any of the very informative deep stop threads here, you would probably assume that the issue has been thoroughly settled. You have read the words of true experts in the field, and you have seen the recent research studies. You know that leading researchers no longer support deep stop methodology. You have come to a decision that is truly based on the most recent thinking by the leaders in the industry.

But what if you were a serious, conscientious diver who was not part of these ScubaBoard discussions? What if you had heard about deep stops, as an example, and wanted to know the latest thinking on them. What would you do?

My guess is most of you would start with Google, and you might put in a search phrase like "Scuba diving deep stops." So that is what I did, and I was appalled by the results.

• The featured quote that leads off the results is from Dr. Peter Bennett of DAN, and it firmly endorses deep stops. If you read the full article, though, you see that he pulls that punch in the full discussion, and you will further see that it was part of a panel discussion, with all other members of the panel strongly disagreeing with him.
• The second article quoted is also from DAN. It is a 2011 article promoting deep stops. There is a statement with it that says that the article does not reflect current thinking, but I suspect that people will read the article rather than note that it does not reflect current thought.
• The 5th article has a strong title, talking about the importance of deep stops in 2018--so it must have the latest and greatest stuff in it, right? Nope. There is no information in there that comes from the last 15 years, and it is a full-on endorsement for deep stops in all diving, including recreational diving.
• The 15th article is a strongly worded endorsement appearing on the web site of a major scuba agency--GUE. The article itself is undated, but the copyright statement on the bottom says 1998-2018, indicating to the casual reader that it is current thinking. This article says that your first stop should be at 80% of the depth of your profile--now that is a deep stop! Knowledgeable readers would know from the article's author (George Irvine) that the information is dated, but most readers would believe that the practice has the current GUE seal of approval, because there is nothing on the page to say otherwise.
• None of the heated and highly informative ScubaBoard threads appear in the first 10 pages of search results--which is as far as I went.
• In those first 10 pages of search results, I saw only a couple of results casting doubt on the efficacy of deep stops, and one of them was the aforementioned DAN article that had the non-representative quote from Dr. Bennett as an excerpt.

In short, if I were to research current thinking on deep stops using Google as my guide, I would come away absolutely convinced that the latest and greatest thinking on deep stops is that they are absolutely and unquestionably the way to go with my diving--the absolute opposite of what is actually happening with current thinking.

So--where is a diver to go to find out what is going on in the world of scuba diving?

There is a well established solution to this problem. You author an encyclopedia article on the subject. Your peers review it and flag parts of the article as needing change or make changes to it. After a little back and forth and a lot of vetting, you have a solid article about deep trimix diving procedures. When research changes the group think, someone updates the article and the process repeats. Each time the article must provide external references (ideally to published research as was referenced in the deep stop thread). It's a robust and elegant system.

Try it out today: Wikipedia It's the worlds largest encyclopedia by a country mile and the single greatest repository for human knowledge. It's also free. There are some who naysay encyclopedias and/or wikipedia. But there are naysayers for everything. Some people still believe in deep stops, others still believe the earth is flat (really, they're out there).

 

[boulderjohn]

the belief in the danger of reverse profiles comes from not even trying to understand the issue in terms of established deco theory.

The story behind the reverse profile banning is a perfect example of a process we see in pretty much all walks of life, including scuba, a process by which a simple idea gets amplified over time into a hard and fast rule, with no one truly understanding the point behind it. It is a good illustration of the need for an easy way to get to good information.

A 2001 conference on reverse profiles tried to determine the origin of the rule. It was determined that the first time it ever appeared was in a 1972 PADI OW manual. It suggested that a diver doing two dives should do the deeper one first. There was no explanation for it in the text, and PADI members in the conference did not know who put it in or why. In subsequent editions, that suggestion turned into a rule, with each new version more strongly stated. No reason was ever given.

With a little thought, the most likely reason for the original suggestion becomes evident. At that time, they were using the US Navy tables to plan dives. Those tables based surface intervals on the 120 minute compartment, so divers doing 2 dives had to wait a long time between dives. That length of time depends to an amazing degree upon the order of the dives. Do the shallow dive first, and you will be out of the water a long, long time before doing the deeper dive. Doing the deeper dive first is not a safety issue--it is a matter of getting a 2-tank dive done in a reasonable amount of time.

I have seen the same process play out in other areas of scuba. Decades ago someone got an idea for a simple way to show OW student that inhaling makes them more buoyant and exhaling makes them less buoyant. That was the entire purpose of the exercise that became known as the fin pivot. Before long the fin pivot became a skill with precise and exact rules, and it could take a student a half hour to perfect the form to an exacting instructor's satisfaction. PADI eliminated it from the OW course about a decade ago, but instructors around the world have not figured that out and are still demanding perfection on a skill that has nothing to do with scuba.

 

[2airishuman]

So how does a scuba diver keep up with changes in scuba knowledge?

In general, they don't. Scuba divers, like most other people, ignore information that does not agree with their current point of view.

Beyond that, I would question the applicability of the example. Like much in SCUBA diving, and in particular like much of that part of SCUBA diving that is outside the "recreational tourist boat diver" sort of box, deep stops were never based on especially sound science, and the repudiation of them -- though evidence-based -- is not based on multiple rigorous well-controlled studies nor is it based on a complete, thorough understanding of DCS (such understanding being, thus far, elusive).

In all disciplines, there is a lag between conclusions being drawn from research, and broad implementation of these conclusions by practitioners. There are, for example, thousands upon thousands of unnecessarily invasive surgical procedures being performed, because surgeons typically do not change their method of performing a procedure once they have learned it.

Add financial motives to the mix and things get murkier. Consider the "shoe fitting fluoroscope" Despite the uselessness of the device and the fact that the health hazards were known shortly after its introduction around 1920, the last of these things was still in use -- in Boston -- in the 1970s. Because customers liked them and they sold shoes. Such is the human capacity for ignoring inconvenient facts.

I don't think SB is necessarily the answer, either, because there's a herd mentality here, too. It is instructive to look at 10-year old threads and see how the advice has shifted over time.