Changes in my personal decompression regime

[Tortuga68]

Thanks for sharing, very interesting

For the purpose of this study, deep was defined as below 230 feet.... After my first two days of deep dives 330+...I continued to dive for four more days with dives in the the 200-330 range and one in the 450+ range

Can you tell us the full depth/time dive schedule for your week?

 

[LiteHedded]

Very interesting information, especially that he recommended extending the SHALLOW stops. I would have thought, given the theory of bubble formation and expansion, that bubble control would be better done deeper.

This is the sane thing the nedu experimental tables are doing

 

[LiteHedded]

At certain exposures. It
Changes on longer ones to require more deep time...

 

[Tienuts]

Kim, great information - thanks for posting!

Question: did you get an opportunity to chat with other divers diving similar profiles as you, besides out normal gang, and were they getting similar test results? If so, did most divers applying that 30/70 setting work for then too?

I've always used 25/85, so I'm not too far off on the deep stop setting, but the shallow stop setting is off a bit more, 70 vs. 85. That's why I asked the question about other divers results, because I understand the individual nature of these results, but I was wondering if you observed any patterns? I like the idea of being conservative in the water, but I do get tired of looking at Jeff and Tony on the longer hangs!

As you know I've always used an X1 set to VPM+3 and a Shearwater Predator GF set to 25/85. This was for the same reason you did Adrian - our instructor simply told us to do that. I would always dive, allowing both computers to clear.

While I did not partake in the full study, I did get many bubble scans done by the DAN staff. I found after one dive, I was also bubbling at 4-5 level, and then made a switch to 30/70. After this change, along with the light exercise during deco, I found my bubble scores dropped to a 0-1 post dive.

Very interesting information, especially that he recommended extending the SHALLOW stops. I would have thought, given the theory of bubble formation and expansion, that bubble control would be better done deeper.

Dr Polluck gave a presentation on this, and while he never speaks in absolutes, he expressed his dislike for deep stops. During an informal Q&A session, I directly asked him his opinion on VPM. He wouldn't say anything other than that studies and evidence indicate deep stops do more harm then good.

I also chatted with Bruce Partridge of Shearwater. He spoke to me about VPM and deep stops, and how there was a several million dollar study done (US Navy I think) to prove that VPM with it's deeper stops was a more effective way to decompress. Turns out the study revealed that it's not. Bruce can fill you in with more details.

I was a big fan of VPM, and used it on all of my diving. After speaking with Dr Polluck, Bruce Partridge (both whom I have tremendous respect for) and the limited feedback I got from the bubble study, I've switched to GF 30/70, and stopped using VPM all together.

Thanks for sharing, very interesting



Can you tell us the full depth/time dive schedule for your week?

Kim and I did similar dives for the week. I did 11 dives over 7 days, 8 of those dives were in the 280-330 range with one dive to 460. Runtimes were generally between 1.5-2 hours.

Tony

 

[Tortuga68]

Thanks Tony

Kim and I did similar dives for the week. I did 11 dives over 7 days, 8 of those dives were in the 280-330 range with one dive to 460. Runtimes were generally between 1.5-2 hours

I'm specifically interested in the daily profiles - were they reverse?

 

[gkndivebum]

[...]Dr Pollock gave a presentation on this, and while he never speaks in absolutes, he expressed his dislike for deep stops. During an informal Q&A session, I directly asked him his opinion on VPM. He wouldn't say anything other than that studies and evidence indicate deep stops do more harm then good.

I also chatted with Bruce Partridge of Shearwater. He spoke to me about VPM and deep stops, and how there was a several million dollar study done (US Navy I think) to prove that VPM with it's deeper stops was a more effective way to decompress. Turns out the study revealed that it's not. Bruce can fill you in with more details. [...]

This was presented at the Decompression and Deep Stops Workshop held in Salt Lake City 24-25 June 2008. To say that there were contentious discussions pro/con deep stops would be an understatement. The study in question is titled

Deep stops and their efficacy in Decompression: US Navy Research - Gerth, WA; Doolette, DJ; Gault, KA.


Copies of the proceedings from that meeting may be available at a good university library and are available for purchase here.

Another interesting paper from that conference has to do with the relevance of post-dive Doppler scores vs. incidence of DCI: Bubble Detection and DCS Relevance - Pollock, N.

 

[Tortuga68]

Abstract: http://www.swiss-cave-diving.ch/PDF-dateien/Rubicon_DeepStop.pdf

DAN Tech Proceedings: http://archive.rubicon-foundation.o...56789/8300/1/DAN_Tech_Proceedings_Feb2010.pdf

 

[Tienuts]

Thanks Tony

I'm specifically interested in the daily profiles - were they reverse?

Reverse as in shallow dive followed by a deep dive? I can't speak for Kim, we didn't always dive together, but I had 1 day where I did a 80 foot dive in the AM, followed by a 250 foot dive in the afternoon. I don't believe I was bubble scanned that day.

Tony

 

[Tortuga68]

Reverse as in shallow dive followed by a deep dive?

Yes

I had a discussion with John Lippmann from DAN recently and he mentioned the correlation they see between DCS and reverse profiles; of course DAN only sees a particular segment of diving (ie people that get bent). I made a post about it in T2T (which I subsequently asked to be moved to Dr Deco) but didn't get much feedabck; so, I'm still interested in 'real world' data

 

[Tienuts]

I have no know idea if reverse profiles are bad or not. I've heard arguments both ways over the years.

It would seem to me that a shallow segment of a gas loading prior to a deep segment should have no bearing one way or another. Gas loading is gas loading, right? Dive computers take whatever loading into effect, and plan accordingly. This can also be dictated by the dive site - many caves for example, or even the shore diving in Cayman. Many deep dives there are done with a shore swim, which includes a 20 minute swim to the deep wall at a depth of 40-80 feet prior to your decent.