Plus if you are subclinically bent at 20ft, if you extend that hang around time long enough you can potentially avoid being clinically bent bent on the surface.
Is there data on how close to NDL undeserved hits occur?
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RedSeaDiver2
Contributor
A very interesting read - many thanks to all who have contributed.
broncobowsher
Contributor
Since this is asking for the data on getting DCS when they didn't expect it, don't forget the other half of the data, those that didn't get DCS when they should have.
That would give a better picture of what is going on and how conservative to current algorithms are. Paint the picture on both sides of the line.
(You are not going to find that data either)
That would give a better picture of what is going on and how conservative to current algorithms are. Paint the picture on both sides of the line.
(You are not going to find that data either)
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Who should get DCS? This is just as hard a question as how close to NDL for an unexpected hit. It depends quite a bit on what the NDL is.
I dive to 80 feet on 32% for 43 min and then make a normal direct ascent to the surface. If my Teric is set at 35/75, I have exceeded my NDL by 15 minutes and blew off the deco stops. If my Teric is set to 45/95, I still had a minute of NDL and it was a no stop dive. Very hard to capture the data you would want.
broncobowsher
Contributor
That's the point. It is a question that you can't get an answer for. But it is the other side of the line. Actually puts the line into perspective. In the cloud of data points, where is the line? How wide is the band of data. Don't hyper focus on a tiny data window, look at all of the data.
I think this exchange gets at the heart of the question.
If I gave 100,000 divers a Perdix and made a graph of the surfacing GF99 of every diver who got bent, what would the curve look like?
I would hope to see a curve with the same sort of knee that gave Gavin Anthony the ability to say 6g/l is an inflection point for CO2 retention, as @Dr Simon Mitchell has so eloquently pointed out.
Is there a SurGF at which the data begins to show an increase in risk? I'm sure there's a spectrum, as there is in all human data. But I'd bet we could find a GF at which folks shouldn't be surfacing. Like 95.
If I gave 100,000 divers a Perdix and made a graph of the surfacing GF99 of every diver who got bent, what would the curve look like?
I would hope to see a curve with the same sort of knee that gave Gavin Anthony the ability to say 6g/l is an inflection point for CO2 retention, as @Dr Simon Mitchell has so eloquently pointed out.
Is there a SurGF at which the data begins to show an increase in risk? I'm sure there's a spectrum, as there is in all human data. But I'd bet we could find a GF at which folks shouldn't be surfacing. Like 95.
My understanding is, Surfer GirlFriend only accounts for the leading tissue compartment, fast ones tolerate greater supersaturation spikes, and getting bent with SurfGF 95 in the 5-minute TC may well be less likely than with SurfGF 85 in the 27-minute TC. For all we know integral supersaturation might be a better metric.
Of course it may well be profile-dependent as well: maybe SurfGF 95 is fine for deep bounce dives but not for long shallow ones, etc.
I knew I could count on you for a more precise analysis of the question. ISS - yes!
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