Ascent rates. Why do you choose to do it the way you do it.

[msg]

I, too, learned the 60fpm back in the late 80's. When I got back into the diving scene, I learned that they were now teaching 30fpm. It does feel a bit strange to come up that slow, especially when the computer beeps at me, but it is safer, so why not.
My computer now makes me feel like I did something wrong when I go a tad faster than it thinks I should.

 

[Cacia]

especially when the computer beeps at me,

why is it beeping?

 

[TSandM]

Ed Hatfield, the reason you can't find anything about deep stops in the PADI OW materials (or the AOW materials, or the deep specialty materials ) is because it isn't there.

Different agencies are teaching different things. I believe NAUI is teaching the half depth stop and then a 3 minute safety stop in the shallows. PADI is teaching a 3 minute stop in the shallows, and their written materials say 60 fpm, but the instuctors I had taught 30.

GUE teaches minimum deco, which is the half depth stop, followed by 1 minute stops every ten feet to the surface.

All of these ascent strategies must also be combined with the relevant tables, because tables and ascent profiles go hand in hand. You can't dive GUE deco limits and do PADI ascents -- or you CAN, but you might well get hurt doing so.

And then a lot of people simply follow their computers, watching ascent rates, and stopping when told, and what profile that gives you depends on the model the computer is using, and sometimes how you have programmed it. (For example, my Aladin allows me to request deep stops if I want them.)

 

[Nemrod]

I don't notice any difference in the way I "feel." I don't notice any difference on nitrox either, I don't notice any diffrence with fast or slow ascents or any of that. If you ascended fast enough or went over deco limits such that you don't "feel" good, that might be because you have been bent or it might be a group psychosis or it might be you are in fact tired.

Then I had a group of well trained divers explain to me that every diver gets bent every dive but it is just subclinical. You know what, hogwash!

I went well into deco a few years ago and then was unable to complete the required stops. It is a long story, a strange one with complicating and unforseen happenings. Anyways, I figured I was bent, then I got distracted by another unforseen circumstance and forgot all about being bent. Sooo, I don't guess I was bent. Fact is I felt fine after my hypochondria subsided.

N

 

[danclem]

This is an interesting post. Does anyone know what the eight specific "compartments" are in the ZH-L8 ADT algorithm that UWATEC uses to compute microbubble formation and ascent rates?

There are two bars each for central nervous system, skin, muscle, and bone. I am not a physician, but would like to understand if there are specific tissues that each bar represents. Attached is a copy of the graph that appears on the dive computer and dive profile in the log.

Thanks to any of the experts!

Dan

 

[Charlie99]

I can't give you specific numbers, I'm pretty sure that the bar on the left is the fastest compartment, the one on the right the slowest.

While there isn't really a one-to-one correspondence of tissues and model compartments, it is generally considered that things like spinal cords are in the 12 minute halftimes, while muscle and bone have longer halftimes.

http://www.gap-software.com/staticfiles/UnderstandingMvalues.pdf has info on the 16 compartments of the ZH-L12 and the 16 compartments of ZH-L16, but no info on ZH-L8 ADT unfortunately.

In some of the Uwatec manuals, they do say that the range of halftimes for ZH-L8 is 5 minutes to 640 minutes, which is close to the 5 minute to 635 minute range of ZH-L16 compartments 1b to 16.

 

[TSandM]

"Compartments" are boxes in the theoretical model. They do not represent actual structures in the human body. Highly perfused structures like the central nervous system are thought to behave similarly to the short half-life theoretical compartments, and errors which the models would predict would impact the short half-life "tissues" tend to produce central nervous system symptoms. But as I have said before, there is almost no work done with probes in various parts of the body to measure actual nitrogen tensions, and see how they relate to the compartments in the models.

 

[captain]

The Edge computer has one of the best and most imformative displays of any computer since it came out in 1983. It's 12 tissue bar graph gives a sence of how the decompression model works during the dive. Also notice that the accent rate is 20 fpm normal and 40 fpm in an emergency. I still use it as a back up computer on some dives.

 

[Walter]

The Edge has the perfect display. Nothing else comes close.

 

[danclem]

Thanks for the information. Charlie99: the article by Baker helped considerably.

Looks like another bit of outside reading to figure out how to better understand the tissue loading algorithms. And I thought all I had to do was follow the ascent rate and tissue loading bars on my UWATEC!

Cheers,

Dan