2nd Dive Deeper -- Is this the new recommendation?

[Charlie99]

A diver was recently telling me that the latest, improved dive planning procedure is to ignore the 1st dive in calculating the 2nd.

This method supposedly is correct, if 1) you avoid bounce dives, and 2) the average depth of the 2nd dive is DEEPER than the 1st dive.

Is this really valid? Are PADI, DAN, and others really teaching us wrong by recommending that the 1st dive be the deeper one?

Charlie

 

[Walter]

No.

 

[jbd]

on this site for reverse profiles or reverse profiling. I think that they idea behind this has to do with bubble "crushing". I wouldn't consider it as THE recommended way to plan your diving. Especially when you have heard it from one diver.

 

[Soggy]

I would call that recommendation, "How to get bent without even trying."

 

[Charlie99]

Supposedly, 2nd dive deeper is the DIR method.

"... repetitive diving is a good thing, and you should do your shallower dive first and then your deeper one. The stupidity taught in that regard is beyond the pale. "

and

"From a decompression point of view, we have seen that repetitive diving makes no difference, so we ignore the first dive in calculating the second. The only trick is that the second dive should be deeper than or equal to the first, and you can not bounce dive after a dive of any kind. "

Good advice, or bad?

 

[MikeFerrara]

Well...we know who wrote that. Maybe it works for him but I don't think GUE teaches it. and I don't think there are any physiologists that will back it up. BRW, thinks it's a bad idea and he developed RGBM. Do a search on the board and get it in his own words.

 

[Doppler]

Charlie99 once bubbled...
Supposedly, 2nd dive deeper is the DIR method.

"... repetitive diving is a good thing, and you should do your shallower dive first and then your deeper one. The stupidity taught in that regard is beyond the pale. "

and

"From a decompression point of view, we have seen that repetitive diving makes no difference, so we ignore the first dive in calculating the second. The only trick is that the second dive should be deeper than or equal to the first, and you can not bounce dive after a dive of any kind. "

Good advice, or bad?

Charlie: not sure we should point to this as a DIR thing, since that philosophical stance does not hold any exclusivity on VPM and RGBM deco theories. And I think we may be taking this out of context.

The mention of "crushing bubbles" is approximately correct. The deeper last concept comes from a belief that diving deep will crush bubble nuclei -- residual from earlier dives -- and lessen the chances of seeding bubbles on the subsequent ascent. However, as always with deco theory, it's easy to tell half the story and get yourself into terrible **** because the secret lies in the other half... gases, ascent rates and depth of stops.

Good advice or bad? Well, how comfortable are you testing the theory for yourself

 

[ElectricZombie]

You cannot just ignore the 1st dive, you need to take that into account when planning additional dives.

I can see how an 2nd deeper dive might help prevent serious bubble formation but, I think that doing deep stops and having a good ascent rate would probably do more good.

 

[Charlie99]

Doppler once bubbled...


Charlie: not sure we should point to this as a DIR thing ..

It was a DIR diver telling me that PADI and DAN had it all wrong. I've found what I think is his basis for his statements and quoted it above.

The quotes are from an article written for GUE's Quest discussion forum by George Irvine, head of WKPP.

Repetitive dives.


In this article he makes a good case for not considering residual nitrogen at all when calculating the 2nd dive profile. He also specifically says that the 2nd dive should be DEEPER than the first.

So my question remains, is it "stupidity" and "beyond the pale" to do your first dive deeper than the 2nd; and to take into accound the nitrogen loading from your 1st dive when planning the 2nd ?

Charlie

 

[WreckWriter]

I think a more reasonable statement might be that the thinking is turning towards the old "first dive deeper" thing may not be as critical as we once thought.

WW