DAN optimal path presentation?

[Slonda828]

Hi everyone,

I was just reading through DAN's "Optimal Path" online seminar, and it seems to support that dive profiles utilizing deep stops have a higher rate of DCS than dive profiles using a shallower decompression profile. I was wondering if anyone had any thoughts on this. My intro to tec class pushed deep stops really hard, and I am wondering what others have learned from their independent research. I am not a scientist, so if I am interpreting this data wrong, them by all means correct me.

The seminar is located here:

https://www.diversalertnetwork.org/training/seminars/seminars.aspx

 

[divin'dog]

I read the same thing in one of their Dive Alert issues a while back. I couldn't remember the issue but remember they said that deep stops seemed to have more incidences of DCS. Now there's another by DAN here:
DAN Divers Alert Network
which says that deep stops are beneficial...
Go figure?

 

[vjanelle]

I think it was more of the fact that people were using 3m ascent rates for ratio deco, etc? And this is causing the tissues to become super saturated?

 

[hudson]

Also see this:
http://marsvinet-lillebaelt.dk/index.php?option=com_content&task=view&id=62&Itemid=44

It seems increased DCS risk with deep stops is observed with deep deco dives to 170-190ft but dives <100ft seem to benefit from the deep stop.

If anything it's a good case for NOT adding an arbitrary deep stop to your calculated deco profile.

 

[Blackwood]

I wonder if people who do deep stops on average might be diving more aggressive profiles in general.

 

[Mr Carcharodon]

Hi everyone,

I was just reading through DAN's "Optimal Path" online seminar, and it seems to support that dive profiles utilizing deep stops have a higher rate of DCS than dive profiles using a shallower decompression profile. I was wondering if anyone had any thoughts on this. My intro to tec class pushed deep stops really hard, and I am wondering what others have learned from their independent research. I am not a scientist, so if I am interpreting this data wrong, them by all means correct me.

The seminar is located here:

https://www.diversalertnetwork.org/training/seminars/seminars.aspx

What the DAN seminar shows is that not all deep stops are equal. The first stop was a bit shorter, and the last stop was long, but all the intermediate stops were equal in length. Assuming all the deco was done on the bottom mix VPM would use a more exponential shaped curve rather than the generally linear one used for the study. In general we know that if you stay too long deep the efficiency of decompression will be worse than it could be. They did provide a data point that showed a set of deep stops that were excessively long. But they likely did not find the optimal deep stop profile. Of course too short does not work either.

It is interesting that they did not consider any of the bubble models.

 

[Slonda828]

So, in English, does this mean that using Vplanner is still a good idea or not? I have to be honest here, I do not really care about the science that much, I just want to use the safest (although I know that no method is truly safe, blah, blah, blah) profile that I can with the available information. According to DAN's presentation, it seems that the new Navy tables are pretty good. I have also had success with Vplanner. Based on something other than random opinion, where does one get this type of information?

Blackwood, in the presentation the profiles for the dive itself where the same, the only noted differences in the test data were in how deep the diver stopped on his ascent profile, and for how long. Although you may be right, that is not the case in the way DAN presents the information.

 

[Blackwood]

Blackwood, in the presentation the profiles for the dive itself where the same, the only noted differences in the test data were in how deep the diver stopped on his ascent profile, and for how long.

I couldn't get it to pull up when I first replied (on my phone). I'll check it out shortly.

 

[Slonda828]

I couldn't get it to pull up when I first replied (on my phone). I'll check it out shortly.

Please do when you get a chance. Maybe between the two of us we can make some non-medical doctor sense out of it. You may be sharper than me, but it is written pretty far above my level in some parts.

 

[hudson]

This thread and the PDF within is also relevant:
http://www.scubaboard.com/forums/as...18-deep-stop-rgbm-statistical-validation.html

Besides validation of RGBM model based on trimix data, it also displays the results of two deep air tests, which shows a lower risk following the RGBM profile with deeper but shorter deep-stops (where the deep stops start at ~120ft for 0.5min-1min) , compared to no deep-stops and more sharply to shallower but longer deep-stops which fare worst of all.