DCS is not at "epidemic" proportions, but it does occur. Erring to the conservative side of practice is not about "aesthetic appeal," it is an acknowledgment that our true level of risk is not currently (simply because of all the variables that we cannot measure in a meaningful way), and a healthy concern for the potential adverse effects over time of decompression insults that are just below the level of clinical perception. It is reasonable to think of ways to err to the conservative. The fact that many changes in practice do not have to detract from what can be achieved on a dive makes it easy.
We do not have good injury rate estimates, but, in any case, I would look at the situation a different way. If you are bent, that single case will be far more important than any statistic. DCS occurs, so it makes sense to dive as though you are not bulletproof. It is particularly important to appreciate that being able to dive in a certain way once (or many times) is not a guarantee of future safety. We age or we die; and aging, for a host of reasons, increases our risk. Building in conservative practice wherever feasible helps to make a long and safe diving life possible. Risk tolerance is a personal thing. I have no problem with those who are fully informed taking on risk. I have a problem when they encourage others to take risk without complete information or knowledge of their susceptibility or risk tolerance.
I am not a fan of blanket pre-screening for PFO. I am a fan of encouraging everyone to dive as though they have a PFO. If bubble formation is controlled, the presence of a PFO, particularly a small one, is irrelevant. This brings us back to building in conservatism - why not? No one is a hero for getting out of the water a littler earlier. Getting everyone home safely without concerns is much more important.
Hi Neal,
That's all fine and well. Some people need or seek reasons to justify adding extra safety and will happily accept this extra. Unfortunately this kind of feel good reasoning turns into a snowballing effect. Last years extra becomes this years standard requirement. It's been going on for years.
I would think that DAN with its mountain of data and access, could come up with some meaningful trend lines for treatment numbers, and overall total tech diver number trends. But lets be honest - a declining treatment rate doesn't fit the narrative, doesn't help the insurance sales business, and goes against one influential person agenda.
From the public information we have DAN + BSAC reports, at least 4 studies, various bits, and simple deductions, over the last 15 years we can say that tech treatment rates have been in a slow decline, while tech diver participation has grown significantly. During the same period the predominant deco was deeper stops, VPM-B, or GF emulations of that style. Obviously we were all heading in the right direction, by design or by luck.
Now the point of this is to say, the deco profiles from over 15 years ago, was with deco on raw ZHL, or a USN 56 derivative, or a table from a book with ties to USN, or GF numbers that were fast, various other planners. Back then people would get DCS from plainly going too fast, and being over the edge. But today that cause is rare, because all our plans have grown longer over the last 15 years, and we have better dive disciplines, procedures and better time keeping.
How is modifying the existing planning going to help today?
Almost no one gets bent from going too fast now days, therefore adding 10 more mins cannot solve a cause that does not exist.
The large PFO people you want to save from injury, have a defect that probably cannot be solved or made good with just 10 extra mins of deco. The lowering of the VGE score one notch probably isn't enough either. We also can't totally eliminate bubbles with any kind of realistic plan, so 10 mins extra doesn't really solve the larger PFO problem at all. And as I said before, the people who have discovered and experienced issues from large PFO, have already tried to prevent and self modify plans with extra deco time, and they still get whacked from time to time.
You see the conundrum? This extra time is aiming at a mid point that doesn't really help anyone. For the vast majority, their deco is sufficiently done already and lowering the bubble score another notch, simply amounts to a feel good cosmetic change only. For the large PFO people, its doesn't go far enough.
The aging diver will probably benefit, but its already recommended and standard practice to go longer as we age. And the smarter aging diver tends to avoid higher risk dives altogether.
Perhaps the real improvement will be with the "sore elbow" people. 10 mins extra might reduce or avoid that, by doing it in the water, instead of later on the surface. However, the onset probably needs surface condition to manifest, so maybe it won't help much. But then these people never needed a treatment anyway. Again I wonder what's really going to change in the big picture?
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I think this message of yours / Simons is selling a false hope to the ones who need it most. You have no data or information that large PFO people can be made normal by adding 10 mins. You can't be claiming real improvements based on slight conditional changes in the theoretical cause.
This is why I think the large PFO people need to be found before they get injured, and that will be the only effective solution for them.
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Using properly timed and sufficient deco, is not about being a hero. When I'm in green water, looking at passing Lionsmane jelly fish tentacles, and getting cold, then less deco time is important. Its about getting out when the deco job is done.
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Finally please tell us your thoughts on how arterialized VGE do not block the capillary, but instead elongate and pass through the capillaries (elaborate on the recent BSAC question period answer you gave). I think many here will find that an interesting point of view.
Thanks.
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