Current Research on Deep Stops for Recreational Divers?

[Kingpatzer]

However, an ascent rate of 60 fpm from 120 fsw with a 1 minute stop at 90,60,30, and 15 fsw (just to use Thal's scenario) would be 2 minutes plus 1 minute at each stop (4 stops) for a total of 6 minutes to cover 120 feet (120/6=20) which would really in that scenario be an ascent rate of 20 fpm.

Which is though, only part of the issue. Add on top of that the general lowering of total ascent time and a second issue becomes present -- that we're simply not managing pressure gradients change on ascent very well. The older the table, the longer the time required for ascent (with the exception of a few technical diving protocols). Even old PADI tables had deco stops on them.

The paper, in my reading, suggests that not only should the ascent rates be changed, but that stops which should be added will be long enough to give a much longer total ascent time. Even though it will be longer, it will be more efficient at allowing for pressure equalization than merely coming to the surface in the same time interval at a linear ascent rate.

 

[gcbryan]

I was finally able to read the paper. I found parts of it a bit odd. Using Buhlmann's algorithm to determine tissue nitrogen tensions. I guess there is no other way but using an algorithm to test itself is odd.

Using only 22 people in a study where we know individual variety is large seems like a small number to me.

I do now see what they were referring to when they talk about faster tissues being de-emphasized today. In Haldanes time the ambient tolerated pressure ratio was more or less the same for all compartments..slow and fast. Today the ratio is much greater for the faster tissues as opposed to the slower tissues. They (and others) suggest in effect reducing some of those differences.

As far as some of the conclusions and the design of the actual study I don't find it all that compelling in some regards. They are exceeding the NDL's so I don't find it that hard to believe that they got more bubbles from a slower ascent since they were just ongassing more and since they had no stops to allow time for bubbles to reduce. It probably was better to get to the surface but if they hadn't exceed the NDL's then perhaps the slow ascent would have been enough time for smaller bubbles to reduce. Who knows?

The slow ascent seemed to work well with stops. In this case I'm referring to 30fpm as slower.

I think what they really showed was just that it's better to have a couple of stops than to not have them. Not exactly earth shaking conclusions.

Although they didn't list it as a conclusion I think reducing the range between the allowable overpressurization ratio between fast and slow is probably a good idea.

Anyone else interpret this differently?

 

[Funky556]

I gleaned emphasis on the time at those stops and the ascent rates for those stops. Such as less deco time in deep stops and more time at shallower stops. But you have to understand for a guy with 6 dives under his belt this is all pretty neat for me. So take some of this with a grain of salt

 

[Puffer Fish]

I find this a terribly interesting subject....and Funky.... don't think making a lot of dives makes one any smarter on the issue...

I found that paper to be terribly written, missing a ton of detail and rather jumping to conclusions.

First off, how accurately did the people accend? The next issue with the continous slow accent is that besides being difficult to do, it is reasonably easy to calculate the equavalent gas tension to a stop (which by definition would be shorter)...in fact that goes for all the times and methods...I also question their correlation evaluation and what it meant.

But there is some interesting data...would have been nice if they would have managed to come up with a model that explained their varied readings...but given that they went for a 0-4 scale and then a 0-10 scale, I am guessing their math skills are not the best.