Deep Stops Increases DCS

[Kevrumbo]

Ross, all the arguments pro & con and the potential issues of the applicability of the NEDU study are academically interesting and compelling. I hope a fair experimental paradigm can be designed in the future to test the validity and resolve these issues above.

But whatever it takes for this old body of mine to exit the water now without overt & acute DCS symptoms after three or four straight days of decompression diving --if it simply means more O2 time on top of whatever deco algorithm with or without deep stops -- then that's fine with me. . .

 

[Ayisha]

...The outcome of all this by the "experts" was to suggest and adopt profiles like 40/70, which if you look closely, is almost the same as a VPM-B+3 profile. They are not a perfect match, but are close in many aspects.

So its OK to use GF to make and emulate VPM-B style profiles, but not the actual model? That makes the whole argument against VPM-B as hypocrisy.

Yep, and just to be clear to some who may not realize the implication, the 40/70 profile still implements a deep stop even though people think the NEDU study warned against deep stops (as evidenced even in the title of this thread). At the time the NEDU study came out, it seemed pretty clear that it didn't reflect real-world dives or deep stops in the way they're commonly utilized. The subsequent discussion on multiple boards and threads even by those involved in the study or in the field further appeared to confirm a recurring pattern: a short, shallower deep stop combined with a padded shallow stop.

Please feel free to correct me if I'm wrong or misguided.

 

[rossh]

Using CCR diagrams and depths - typical of your diving:

Its easy to see the similarity between VPM-B+3 and GF 40/70. They are a lot closer than the origin of the GF plan (from the ZHL 100/100).

Note; the alignment between GF and VPM-B is coincidental, and they vary in how well they agree at various points.

GF has the advantage that it can be made to emulate almost any model or profile shape. But its interesting the whole argument has come down to pretty much emulating the properties and attributes of a bubble model plan, and then being in denial about it.

I don't think I'd say 40/70 and VPM+3 is a close match.

Lets look at a fairly standard issue dive
200ft, 18/45, 50%, 100%, 30min BT via Deco Planner:

VPM starts stops at 130', 40/70 at 90'.
VPM has a total of 11mins of stop time before the 70' gas switch, 40/70 has 7.
VPM has 28mins on oxygen, 40/70 has 34mins.
VPM's total deco time is 62mins, 40/70 is 66mins.

Imo, id rather get on a deco gas sooner and move VPM's deep stop time to somewhere useful (aka the oxygen stop).

So based on that, you're doing *less* total deco, *less* time on deco gases, and *less* time on oxygen.

Nope.

 

[PfcAJ]

Using CCR diagrams and depths - typical of your diving:

Its easy to see the similarity between VPM-B+3 and GF 40/70. They are a lot closer than the origin of the GF plan (from the ZHL 100/100).

Note; the alignment between GF and VPM-B is coincidental, and they vary in how well they agree at various points.

GF has the advantage that it can be made to emulate almost any model or profile shape. But its interesting the whole argument has come down to pretty much emulating the properties and attributes of a bubble model plan, and then being in denial about it.

Looking at the 240' for 40 plan you posted, uhh....30mins of deco is enough for me to say they're 'not similar'. Even the 20min schedule has what appears to be a stop at 160ft.

PS I don't dive CCR

 

[PfcAJ]

This whole thread is proof of Alberto Brandolini's Bull**** Asymmetry Principle:

The amount of energy needed to refute bull**** is an order of magnitude bigger than to produce it.

 

[rossh]

But whatever it takes for this old body of mine to exit the water now without overt & acute DCS symptoms after three or four straight days of decompression diving --if it simply means more O2 time on top of whatever deco algorithm with or without deep stops -- then that's fine with me. . .

Yes, its an interesting question - what really goes wrong after a 3 or 4 day sequence. Is it accumulated inert gas tissue build up?? Or exhaustion and sensitized and inability of the body to perform the same strenuous task day after day??

I put the question to Dr. Neal Pollock at the recent Tek USA conference. He thought the second was more likely. But he also added that we tend to do the bigger dives later in a multi-day sequence, so that leans towards the first item. Which really leaves the question open.

 

[rossh]

Looking at the 240' for 40 plan you posted, uhh....30mins of deco is enough for me to say they're 'not similar'. Even the 20min schedule has what appears to be a stop at 160ft.

PS I don't dive CCR

Your preferred model started at 100/100, which is definitely shorter in all aspects, and soundly rejected. The preferred GF once used to be both deeper and about the same time as the matching VPM-B. Then it moved to a little more shallow and a bit longer than VPM-B. Are they the the same? No. Similar - absolutely.

And, oh yes, the real world 5m/min ascent that occurs, is functionally the same as 1minute stops at a 10m/min planning rate. So your nit picking of the initial stop depth is meaningless.

When you lot start doing 70/70, with real ascent rates, only then can you lot claim to be doing something new and different. In the mean time, the only thing that separates you from doing VPM-B style profiles, is your denial.

 

[Patoux01]

In the mean time, the only thing that separates you from doing VPM-B style profiles, is your denial.

And the fact that there is 30 minutes difference between 2 "similar" profiles (your words).

 

[PfcAJ]

And the fact that there is 30 minutes difference between 2 "similar" profiles (your words).

Makes you wonder what it would take for Ross to say two profiles are dissimilar...

 

[rossh]

Of course a 40 min bottom time at this depth is beyond most people, and well beyond the normal reach of OC divers,due to the gas volume required. The 40 min profile demonstrates how long ZHL/GF become badly out of proportion due to the extrapolation and GF compounding issue. No one needs that much extra time - look at the 100/100 plan !

If you ignore the GF expotential error in the 40 mins plan,which involves the Last stop only, then rest of the profile is all pretty similar. Go back and look at the more typical 20 min profile. A few minute difference only.

Argument being imagined here, here is they are pretending to "not' be doing deep stops. But in reality, the real world slow ascents (that are not actually planned), mean they are doing the deeper stops.

So they pretend to not to do deep stops, buy in fact really are. And if doing normal length dives, then the finish time about the same as a real VPM-B+3 plan. therfore... still doing a VPM-B style profile.

And the fact that there is 30 minutes difference between 2 "similar" profiles (your words).