Have deco models gotten as accurate as they're going to get?

[Lorenzoid]

While I don't see much changing very soon, technology does not advance on a linear scale (or a very predictable one at that).

Many algorithms are based on estimates of tissue compartments in a generalized manner. What if you could go for a hospital visit, and your body could be scanned for personalized tissue compartment estimates and then cut custom tables for you, or enter this information into your dive computer for a customized profile? Although, I'm guessing some consideration would need to be made for day to day changes such as dehydration.

What if a dive computer could monitor tissue saturation in real time, giving you the absolute maximum no decompression time with no danger of DCS?

I have no reason to believe that any of this is currently being worked on, just dreaming out loud

I've heard that researchers in the field have been dreaming about this sort of individual data-gathering, too, so I suppose that counts as it being "worked on." If they've gone beyond merely thinking about it, it would be interesting to know what's been done.

 

[onwardsupwards]

Not as long as manufacturers are able to release the new latest, greatest, must have, "improved" algorithm/hardware.
Too many $ to be made.

 

[rjack321]

hey, tables did a fine job of keeping you safe. They usually kept you out of the water, so that made you safe(r). We should all go back to diving tables, using square profiles, and at recreational no-decompression limits.... easy.....

Suuntos do the same, at least on the 2nd+ dive(s) of the day.
"Safe" as can be when you're dry

 

[flots am]

New research and new models are helping to map the shape of the black and the white depth/time/deco envelope in greater detail. But isn't it possible that part of the gray zone is statistically impenetrable for any model that only tracks three or four variables, regardless of its algorithm?

I have no doubt that a better algorithm (a better decompression model for humans) could be built, but I'm not so sure that there would be any safety improvement because of it, since it's really difficult for divers to self-assess their own internal condition. Also, I suspect it would be a marketing problem. Nobody wants a computer that's going to limit their dives to be shorter than other divers.

What might be useful (or it might just be a "you're screwed" alert) is a Doppler sensor that would actually monitor bubbles on ascent.

flots.

 

[rhwestfall]

What might be useful (or it might just be a "you're screwed" alert) is a Doppler sensor that would actually monitor bubbles on ascent.

Would make for a faster autopsy....

 

[rossh]

I tend to agree with you - Given that models are about 99.99% successful, its unlikely we can improve on that. Models are required to work with a very small parameter set. I think the next leap of advances will come from individual monitoring systems. But here is the interesting part. When a more accurate picture is available, it will narrow the gray zone. For most divers, that will mean a shorter / faster deco time. I'm not sure that today's diving public is going to welcome that kind of change.

 

[Sir-Dive-A-Lot]

I read an interesting article the other day about the future of dive computers and remembered reading this very thread.

http://smithsonianrex.si.edu/index.php/pop/article/download/320/279

The article states that bubbles do not grow to any decent level until 20-40 mins after a dive, so even if the technology was there to monitor real bubble growth; it simply wouldn't be useful to do during the dive.

But I do like the idea of integrated EPIRBs and GPS receivers nonetheless.

Haven't been able to find much about this Capernicus bubble model unfortunately. However it does look promising if they could pull it off.

 

[Duke Dive Medicine]

Just bumbled across this thread. For what it's worth:

[abstract] DECOMPRESSION RISK EVALUATION OF COMMERCIALLY AVAILABLE DESKTOP DECOMPRESSION ALGORITHMS

There's a more recent abstract that was presented at the 2012 UHMS annual scientific meeting that pretty much mirrored the above study in that decompression algorithms are not iso-risk, that is, the probability of DCS goes up with increasing depth and bottom time. The actual numbers, i.e. pDCS don't mean much since the modeling software is based on U.S. Navy data, but the shape of the curve is significant. It would be great to gather data on actual outcomes vs. statistical probabilities but for now this is the best we have. So, going by current data, it could reasonably be said that the algorithms could be improved to lower the statistical probability of DCS on deeper and longer dives.

Ross, if you're reading this it would be great to hear your thoughts.

Best regards,
DDM

 

[JohnN]

I had a very interesting conversation with one of the developers of Subsurface (Subsurface | An open source divelog). He has spent a great deal of time researching the various decompression algorithms in use by modern dive computers. The short form of the story is that most/all modern algorithms start with a model like Buhlman with multiple tissue types and factors that estimate their propensity to on and off-gas N2. The kicker is when you take the cover off the algorithms, they all introduce 'fudge' factors to make the predicted results better match the empirical results from the decompression done on sheep done back in the late 1990's (Predicting risk of decompression sickness in humans from outcomes in sheep)

You can take this as you wish, but my (perhaps) simplistic conclusion is that no-one really understands why a person will take a DCS hit and predicting it runs perilously close to the old "Measure with a micrometer, mark with chalk, cut with an axe" chestnut.

 

[boulderjohn]

Where would the probe go?

We check blood oxygen right now with a simple device that goes over a finger tip. No probe required. (Yes, that is blood oxygen, not tissue oxygen.) Quite a few years ago I had a neighbor who was an engineer and not a diver. We were talking about diving, and he asked about the demand for such a device that could measure nitrogen levels. He did not seem to think there would be any problem designing something like that, and he was honestly thinking about the feasibility of doing it himself. He concluded that there would not be enough anticipated demand for the product to justify the cost of creating it. I know I would not want to pay extra for that for simple NDL diving, just as I can't see why I would want to pay extra for a heart rate monitor on a dive computer.

Just bumbled across this thread. For what it's worth:

[abstract] DECOMPRESSION RISK EVALUATION OF COMMERCIALLY AVAILABLE DESKTOP DECOMPRESSION ALGORITHMS

There's a more recent abstract that was presented at the 2012 UHMS annual scientific meeting that pretty much mirrored the above study in that decompression algorithms are not iso-risk, that is, the probability of DCS goes up with increasing depth and bottom time. The actual numbers, i.e. pDCS don't mean much since the modeling software is based on U.S. Navy data, but the shape of the curve is significant. It would be great to gather data on actual outcomes vs. statistical probabilities but for now this is the best we have. So, going by current data, it could reasonably be said that the algorithms could be improved to lower the statistical probability of DCS on deeper and longer dives.

I had an email exchange with Gene a few years ago in which he shared some of the findings that made it into this paper. I was asking about decompression diving, while this paper focuses on nitrox diving. The complete exchange was quite illuminating. The conclusion I drew from that discussion is that we do not have anything close to enough data for decompression diving to tell us what we need to know in terms of choosing one algorithm over another. I think we are therefore still very early in the learning process about this. We are all still part of a grand experiment.