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

[rossh]

They all got injured by cold eh? What does your software recommend for cold exposures Ross? Since the NEDU had double the times....and they got injured.

Controlling your thermal status is Your responsibility. You better take it seriously too - see this: TR 2007 06

 

[PfcAJ]

Magic that the deeper profile had more DCS. Literally everything else was the same except for that.

Ugh.

 

[rossh]

Magic that the deeper profile had more DCS. Literally everything else was the same except for that.

Ugh.

Did it not have more SHALLOW STOP gas load - extended time in the 60 to 30 ft range. ???

Which is FULLY addressed in all models and dive computers and all existing planning techniques.


Repeat after me... there are NO deep stops in the nedu test. No amount of imagination will make them magically appear.


.

 

[lowviz]

Yes agreed - its your thread - lets go with that. ...

Maybe more like a continuation thread where we stick to nuts and bolts. First and foremost, I'm not a decompression expert by any stretch of the imagination. Second, I don't do "big" dives. Third, I do dive deco and want to know as much as I can about this fuzzy subject.

As for your permission, Thanks. I'll stay away from anything that looks like how you implemented VPM-B, most likely that will come out if I start making any progress. I'll keep that to myself. I'm only interested in how VPM-B (with no corrections, i.e. conservatism) compares to a standard. The only standard that I have access to is the US Navy Air Table 5. That is clearly an apples and oranges problem but maybe something can be teased out. A big problem too, as that table is highly nonlinear (with respect to deco) in both depth and bottom time. See first two graphs. -extremely hard to get a general "feel' for it.

... But we need to define some terms and objectives.

What is the "required" level of deco? Does a model represent that?
How much margin has been added to each model, and can it be removed to come to a common base line? ...

The required level of deco, the common baseline, for this initial approximation would be the USNAT5. Now if you had similar human tests for VPM-B over the same range none of these epic threads would exist.

... A great deal of a models margin for safety is the hands of the designer, and how he feel or chooses to implement that. How are you going to account and equalize that? ...

I would be happy to start with a graph that shows the deviation between VPM-B and USNAT5 that covers whatever range that you guys are stressing over. Exactly how to show that deviation is most problematic.

Adding conservatism could be done by scaling the fitting equation, scaling the deco requirement (or depth or bottom time) and re-fitting an equation to that. Whatever seems to work best. Don't know.

... How do you propose to compare shallow and deep? There is no tool to do this with so far. The dive procedure is where the DCS injury starts. Clearly the differences with in-dive stress levels are significant. If the compare method does not give value to that aspect, then it becomes just another one side biased to the shallow attack. ...

That is the problem, isn't it? Thus my earlier attempt to put a number to the "bigness" of a dive, think of it as multiplying in an "exposure" value of some sort. Still working on that. Any guidance on this would be most appreciated.

... What about different run times for the same dive? I hope we not assuming that all dives are somehow, magically made equal by using the same end run times? ...

Bubble theory is all about getting out of the water sooner and without harm. Forcing the runtimes to be the same is much like throwing the baby out with the bathwater.

... If it were the navy, it would be a pDCS measure, but they only have data on their own kind of shallow stop based dives - no deep(er) stop data there. ...

That is a fundamental problem, but it is a place to start. Bubble theory, IMHO, has to follow dissolved gas theory up to a point and then it would be expected to begin asserting itself ever stronger with depth and time.

One could construct a VPM-B table and compare it to the Navy Table. The two tables will be more and more different with increasing depth and bottom time. Can you save me an awful lot of work and offer your opinion as to where bubble theory begins to assert itself?

And now for the big question, is there a statistically sound collection of deep dives that support bubble theory of any sort? Not trying to be a pain, but the question has to be asked.

-Thanks.

 

[cerich]

Controlling your thermal status is Your responsibility. You better take it seriously too - see this: TR 2007 06

So you make no recommendations?

 

[rossh]

So you make no recommendations?

Yes, avoid getting cold - it affects your deco dramatically - read the report.

 

[kensuf]

So some science is acceptable and good, others is malarky. It just depends on whether or not you like the scientists and what their conclusions are.

 

[UWSojourner]

The nedu exposures are 2x normal required deco.... NO model makes that much unneccessary deco like the nedu test profiles.

If you think VPM is too short then, that means EVERY model is also too short. So take a REAL HARD LOOK below. Real models all finish in the 90 to 120 min region. The nedu test was double that time at 214 mins. The Nedu divers got injured from the cold (deliberate extra thermal stress) not the profile time.

Then maybe you could come back and retract all the invalid statements above.

Don't you see a major difference between your standard profiles for rec/tech divers that you have in your chart vs. the testing procedure the NEDU adopted?

The divers in the NEDU study were WORKING during the bottom phase of the dive.

If you exert yourself during the entire bottom time of a dive and stick with your standard tech decompression schedules you're at high risk for getting bent. That's been known by tech divers forever. Pyle said that if he exerted himself on the bottom he could never get enough deco.

I've heard rules of thumb that exertion during the bottom phase of a dive is equivalent to 50-100% more bottom time. That's huge. Even if you take something in the lower range of that estimate VPM-B+3 gives you run times very close to the NEDU times when you adjust for the work factor. [And that schedule doesn't look any better when compared to A2 than VPM-B+7 does].

There's a major difference between 1) descending to a wreck/reef and calmly finning around looking at pretty fish, and 2) working during the entire bottom phase of a dive. Posting your chart of standard rec/tech profiles and comparing it to profiles developed for working divers is misleading at best.

 

[PfcAJ]

Did it not have more SHALLOW STOP gas load - extended time in the 60 to 30 ft range. ???

Which is FULLY addressed in all models and dive computers and all existing planning techniques.


Repeat after me... there are NO deep stops in the nedu test. No amount of imagination will make them magically appear.


.

So go look at 220 for 25, 15/55 bottom gas and 50% and oxygen for deco.

Compare vpm+3 and 40/70 gradient factors.

Lemme guess - those are both shallow stop schedules right?

 

[rossh]

So go look at 220 for 25, 15/55 bottom gas and 50% and oxygen for deco.

Compare vpm+3 and 40/70 gradient factors.

Lemme guess - those are both shallow stop schedules right?

These dives have deco that starts 2.5 to 3 times deeper, and is 1/3 rd the deco time, vs the Nedu ones? Different ends of the dive scale.

Are you trying to show me that the stretched out chewing gum GF plan, is not consistent because it has used GF to override ZHL and make it all "fitted' to an idea of what ever one wants today?

.