Son of Deep Stops *or* Waiting to be merged with the mother thread...

[UWSojourner]

Well that's maybe an approach that's easier than arguing about VPM-B +7: Calculating with a factor 2x on bottom time to consider strong on-gassing by workload.

That would seem reasonable since if a diver is exerting themselves they either need to cut their bottom time by 1/3rd to 1/2 and follow the same table they planned for the full bottom time, or have with them tables for 50%-100% more bottom time.

So let's have a look at VPM-B +0 (critical radius N2 = 0.55) for 60min bottom time at 170fsw, and compare the schedule to the NEDU schedules:

I could post the ISS/heat maps if desired. But the story is the same. VPM-B+0-working dive- would be slightly worse than VPM-B+7, but the same patterns are clear. The deep stops cause continued on-gassing that results in higher supersaturation stress at the surface and overall. That's the bubble-model-style deep stop pattern.

 

[David Doolette]

Well that's maybe an approach that's easier than arguing about VPM-B +7: Calculating with a factor 2x on bottom time to consider strong on-gassing by workload.

So let's have a look at VPM-B +0 (critical radius N2 = 0.55) for 60min bottom time at 170fsw, and compare the schedule to the NEDU schedules:

Very good illustration. I think the 2x factor is appropriate. We know that the conditions in NEDU TR 11-06, work on the bottom and cold during decompression, are equivalent to doubling our tripling bottom time compared to more benign conditions (rest, warm). A review of these factors with illustration of these effects and pointers to the original references is in the Risk factors for decompression sickness chapter in the DAN Technical Diving Workshop
https://www.google.com/url?sa=t&sou...1WDFKmBlb5qXqB_mg&sig2=wiCkl9-ARfJ_THFEldiZgg

 

[cerich]

Very good illustration. I think the 2x factor is appropriate. We know that the conditions in NEDU TR 11-06, work on the bottom and cold during decompression, are equivalent to doubling our tripling bottom time compared to more benign conditions (rest, warm). A review of these factors with illustration of these effects and pointers to the original references is in the Risk factors for decompression sickness chapter in the DAN Technical Diving Workshop
https://www.google.com/url?sa=t&sou...1WDFKmBlb5qXqB_mg&sig2=wiCkl9-ARfJ_THFEldiZgg

ummm... "work on the bottom and cold during decompression"??? The during deco part was a misspoke thing right?

It seems to me that cold sans work would be a much worse case than cold with work regarding deco needs... just postulating.

Of course work followed by cold not working during deco would be really bad.

 

[rjack321]

.

ummm... "work on the bottom and cold during decompression"??? The during deco part was a misspoke thing right?

It seems to me that cold sans work would be a much worse case than cold with work regarding deco needs... just postulating.

work = warmish on the bottom and cold stationary deco were intentional (and surprisingly realistic)

 

[Storker]

ummm... "work on the bottom and cold during decompression"??? The during deco part was a misspoke thing right?

It seems to me that cold sans work would be a much worse case than cold with work regarding deco needs... just postulating.

IIRC from one of the papers I've read, the worst case is high perfusion/circulation during on-gassing and low perfusion/circulation during off-gassing, i.e. work/warm at bottom and cold during deco. The best case is the opposite, i.e. rest at bottom and mild exercise/warm during deco.

 

[cerich]

IIRC from one of the papers I've read, the worst case is high perfusion/circulation during on-gassing and low perfusion/circulation during off-gassing, i.e. work at bottom and cold during deco. The best case is the opposite, i.e. rest at bottom and mild exercise during deco.

Indeed

 

[David Doolette]

Your cherry picking David....

From the sentence prior... "The detection of bubbles in any individual
is not diagnostic for decompression sickness (DCS).

Or in more detail... not correlated in way Simon hopes.

No, not cherry picking. You said VGE were not correlated with DCS.

Simon and I have acknowledged, dozens of times on these threads, that "The detection of bubbles in any individual is not diagnostic for decompression sickness (DCS)." The truly bizarre part of this argument is that you are quoting something I actually wrote.

Our point, and the one that makes you uncomfortable, is that if a schedule is dived multiple times, and the median peak VGE grade is, say, 3 or greater, the correlation of VGE and DCS suggests the schedule has a relative high risk of DCS compared to a schedule that results in lower VGR grades.

 

[rossh]

No, not cherry picking. You said VGE were not correlated with DCS.

Simon and I have acknowledged, dozens of times on these threads, that "The detection of bubbles in any individual is not diagnostic for decompression sickness (DCS)." The truly bizarre part of this argument is that you are quoting something I actually wrote.

Our point, and the one that makes you uncomfortable, is that if a schedule is dived multiple times, and the median peak VGE grade is, say, 3 or greater, the correlation of VGE and DCS suggests the schedule has a relative high risk of DCS compared to a schedule that results in lower VGR grades.

Its referencing to conditions like Pulmonary DCS, which is certainly life threatening. However its unlikely to a problem for normal everyday diving procedures.


From the sentence prior... which is the more normal conditions.... "The detection of bubbles in any individual is not diagnostic for decompression sickness (DCS).


The false association is that VGE are some kind of a direct measure or profile stress. They are not. VGE are associated with profile stress only, but not correlated - huge variations exists across individuals, or profiles ,or gas types ,age , prior history and a dozen other variables. There is no 1:1 connection with VGE and stress. Anyone trying to make predictions from that is reading tea leaves.


If the readers stop trying to measure DCS probability from VGE counts, then we can all settle down... but until then, that miss-understanding has to corrected.


See my point... read the next post... not correct interpretations.

 

[UWSojourner]

Your cherry picking David....

From the sentence prior... "The detection of bubbles in any individual
is not diagnostic for decompression sickness (DCS)."

When someone says "detection of bubbles in any individual is not diagnostic for DCS" they are only saying that you don't throw a diver into the chamber when you see VGE, even high grades.

There is zero conflict with that and also saying that detection of high grade VGE indicates a higher risk of developing DCS. Deco models that are known for developing higher grade bubbles on average simply put divers into a higher risk group. More of that group will get DCS than will a group of divers diving deco models producing lower grade VGE on average.

A similar idea -- You don't start chemo if you know someone smokes (smoking is not diagnostic of lung cancer). But you do tell them they are at higher risk of developing lung cancer and hope they modify their behavior.

Higher grade VGE is indicative of higher decompression stress and higher risk of DCS. That's just established fact. It's near criminal for you to downplay research showing higher risks associated with higher grade VGE.

 

[scubadada]

so...were're back where we were with enough less name-calling to remain open