Deep Stops Increases DCS

[rossh]

i know i shouldn't wade into this train-wreck of a thread, but since we're now moving the goalposts to thermal stress, just want to point out that for the NEDU study, it was a wet pot dive with the temperature held at 86f/30c +-2f. thermal stress remained constant and consistent across the entirety of the dive for both profiles.

FACT: No deep stops in the test - only shallow stops.

Go find who ever makes really really shallow stop models, and tell them the about it - its their problem - not mine.

 

[PfcAJ]

The amount of BS that surrounds this test, is unbelievable... it tested extended shallow stops - we don't use those. It tested for thermal stress - we already knows what happens there - nothing we can do to fix that.

therefore.... n/a.

Explain why one profile had more dcs than the other.

 

[rossh]

Explain why one profile had more dcs than the other.

Don't need to. It did not test any deep stops. No tech practices in the test.

FACT: No deep stops in the test - only shallow stops.

Go find who ever makes really really shallow stop models, and tell them about it - its their problem - not mine.

 

[leadduck]

You have fallen into the trap, of assuming the nedu profiles failed due purely to "profile" stress. They did not. In fact due to there exaggerated length, there is almost no 'profile' stress remaining. All profiles failed due to excess thermal stress.

In my table I only use the NEDU result that A2 is worse than A1 in terms of DCS risk. You seem to believe that the thermal stress during the study kind of inverted the order, and that A2 is not worse than A1?

That's interesting, because Bruce Wienke and T.R. O'Leary in their response ("Recent Deep Stop Tests and Data") find that A2 has much higher DCS risk than A1 in RGBM, too. This is a fundamental point in their paper, to show that RGBM estimates the DCS risk in accordance with the NEDU results.

So if you have proof that this is wrong, it would be interesting to see because it pulls the rug from under RGBM.

 

[PfcAJ]

Don't need to. It did not test any deep stops. No tech practices in the test.

FACT: No deep stops in the test - only shallow stops.

Go find who ever makes really really shallow stop models, and tell them about it - its their problem - not mine.

lol you're too much

 

[rossh]

In my table I only use the NEDU result that A2 is worse than A1 in terms of DCS risk. You seem to believe that the thermal stress during the study kind of inverted the order, and that A2 is not worse than A1?

That's interesting, because Bruce Wienke and T.R. O'Leary in their response ("Recent Deep Stop Tests and Data") find that A2 has much higher DCS risk than A1 in RGBM, too. This is a fundamental point in their paper, to show that RGBM estimates the DCS risk in accordance with the NEDU results.

So if you have proof that this is wrong, it would be interesting to see because it pulls the rug from under RGBM.

Deep stops are just a few extra minutes in the ascent. (110-80ft)
vs
The test did 90+ extra minutes in the mid to shallows. (60-20ft)


The test has no deep stop: Tech models cannot provide the fabricated mid to shallow stop that the test used.


The test was over two times longer than needed.

The subjects fell over from thermal stress.
vs
deco program only control profile stress.


Its a chalk and cheese comparison. Two vastly different things.

***********


Thermal stress is very powerful and can ruin any dive. Please see: The Influence of Thermal Exposure on Diver Susceptibility to Decompression Sickness.

.

 

[PfcAJ]

Magic that one profile had more dcs than the other I guess. CANT BE the stop distribution!

 

[KevinNM]

Magic that one profile had more dcs than the other I guess. CANT BE the stop distribution!

But if they had done 50% less deco on A2 things would have been much better, right?

 

[UWSojourner]

All these arguments, or distractions from the issues perhaps, were thoroughly hashed out on the RBW deep stop thread. The scientists involved in the NEDU study believed they had tested their deep stop model against their shallow model. The Navy was ready to move to a deep stop protocol. But they didn't because of this study. These are the guys actually responsible for the safety of Navy divers. I guess Ross is claiming that it's a shame the US Navy doesn't have his expertise to guide them.

Please see the heat map below. It provides a comparison of the supersaturation patterns of 4 profiles -- the 2 NEDU study profiles (A2 and A1) and two models we're all more familiar with, VPM-B and GF. Both VPM-B and GF were dialed in to have the same runtime (209 minutes).

Some things to note:

1. Each profile shows 16 lines of color corresponding to the 16 tissue compartments. The top line is the fastest compartment, the bottom line is the slowest.
2. The colors compare the state of each tissue compartment's supersaturation and continued on gassing relative to the other 4 profiles. So, for example, compartment 10 for A2 is red when the diver surfaces while the other profiles' are shades of red and yellow. The colors roughly show how close each profile's compartment is to the others.
3. The on gassing colors give you a sense of the cost of staying deeper longer. If you look at A2 and VPM, clearly they both "protect the fast tissues" (see the cooler coolers in compartment's 1-5 early in the ascent). But they also show heavier continued gas update in the slower compartments.

The heat map shows visually what Dr. Doolette's "deep stop skew" chart showed conceptually. A2 and VPM skew stops deeper and GF and A1 skew stops shallower. The impact of this skew is seen in the integral supersaturation (ISS) chart below. ISS is an index of time exposure to supersaturation. The only credible theory for the higher DCS rate in A2 is that it's higher integral supersaturation (i.e. diver's exposure time to supersaturation) caused the additional DCS risk. For reference, VPM's ISS is 95% of A2's, GF's is 84% and A1's is 80%.

The nice thing about these charts is WE KNOW the risk of A2 (~5%) and A1 (~1.6%). And you can see the relative similarities of VPM and GF. Many of us have concluded based on these NEDU results that VPM's mechanism of allocating stop time simply allocates too much time deep. And GF's algorithm more naturally skews time in better proportions to shallower depths and, therefore, better reflects the NEDU study.

 

[rossh]

Ignore all references to VPM-B in those diagrams.

There is no such thing as a VPM-B +7. It is FAKE !

They could not make any real connection to VPM-B, so they just made up a FAKE profile.

Pathetic! A deliberate deception.