Deep stops, Pyle stops, Gradient Factor

[Lost Yooper]

Technical diving requires a certain degree of discipline for certain. However, the way we try to decompress (as tought by Irvine et al) is to offgass the most efficiently and thoroughly as possible. Sometimes this means we won't get out of the water as fast as an air diver using Navy tables or a computer. However, we will be better offgassed and feel mucho better than they will.

That said, the way we dive actually has a considerable amount of "fudge" built in for emergency contingencies (ie. if we had to surface prematurely). By incorporating deep stops, slow ascents, and the right deco mixes, we stand a better chance of avoiding serious DCS (if any) than a "technical" deep air diver who doesn't know what he's doing.

Technical diving (even as we do it) isn't really complicated. There's a few rules that you must follow to survive, and a few more to come out feeling like a million bucks. Just like OW diving, if you break the key rules, you will die or get bent. As for cave diving, those guys are just plain lunatics . However, they too have their rules which can't be broken with contingency plans.

Wienke is one of a few who seems to know what's going on as far as deco mechanics. He coordinated a great deal of his research with Irvine and those other nutt cases to get where he is now. VPM and RGBM are great advances in deco programs.

Mike

 

[Dr Deco]

Dear readers:

The deep stops are certainly of value from a theoretical point of view and appear to be of value in actual diving practice - - - a nice coincidence.

While it is true that gas will be taken up by the slow compartments (= “tissues” but they are really not separate tissues) during the deep stops, the advantage of reduction in size of the apparently microbubbles makes up for this. The reason that I use the word apparently is that the whole process depends on the size-number density of microbubbles. This means the concentration (number) of small, medium, and large bubbles in the tissues. This distribution cannot currently be measured in the body because it is not possible to see into the opaque tissues.


The size-number density distribution is measured in some situations such as water tunnels (the hydrodynamic equivalent of a wind tunnel) and the form of this can be used to make deco tables. In addition, the work by Dr David Yount has given guidance to Dr Weinke in the making of his RGBM tables.

In the end, I believe that experience has shown that something in deep stops (probably microbubble size) is influenced by these stops and that this offsets on-gassing by the slow compartments.

Dr Deco
:doctor:

 

[The Chairman]

Well they finally did it! NAUI has officially adopted the rule of halves for ALL no-deco table based open water dives. It was good to be able to present it to my class tonight too.

For dives greater than forty feet, you make your first stop at half of your deepest depth for at least a minute. Then you proceed to 15'-20' for the remainder of your precautionary stop. For dives 40' and shallower, you only need to do a normal precautionary stop.

So, if I made an 80 ft dive, I would ascend to 40 ft for at least a minute before I went to 15'-20' for the rest of my safety stop. Change is good.

 

[mars2u]

NetDoc once bubbled...
Well they finally did it! NAUI has officially adopted the rule of halves for ALL no-deco table based open water dives. It was good to be able to present it to my class tonight too.

For dives greater than forty feet, you make your first stop at half of your deepest depth for at least a minute. Then you proceed to 15'-20' for the remainder of your precautionary stop. For dives 40' and shallower, you only need to do a normal precautionary stop.

So, if I made an 80 ft dive, I would ascend to 40 ft for at least a minute before I went to 15'-20' for the rest of my safety stop. Change is good.

Yes, after thousands of dives being analyzed... deep stops (without changing ascent speed) reduced high bubble grades to nearly zero compared to ~30% without deep stops.
Better to be safe then sorry/ Better to be conservative than sorry.

 

[The Chairman]

they did a metric butte tonne of research. They don't just espouse the theory du jour, now do they?

 

[MikeFerrara]

hehe...There a couple agencies that I'll call soon just to say "I told you so"

 

[mddolson]

Net Doc Bubbled:"Well they finally did it! NAUI has officially adopted the rule of halves for ALL no-deco table based open water dives. "

Net Doc ? That's good news, When did you receive the update?
Being way up here in Canada it can take up to a month before we get our mailings, subscriptions etc. Can you elaberate a little? The NAUI table counts time to the safety stop as dive time, do we now count time to the half stop as dive time?

Mike D
NAUI 4780

 

[The Chairman]

NAUI counts the "whole dive" from the time you enter till the time you surface, then excludes any precautionary stops from table calculations. While not specifically covered in the Sources article, I am sure that you will follow those same guidelines and deduct any stop time from the total. Is that clear as mud?

 

[mddolson]

Sorry for my abreviated description. That is what I meant.
I had presumed that for table (rep group) calculations we would now deduct the 1 minute deep stop and 3-5 minute safety stop from total dive time.

Mike D

 

[plsdiver4377]

I'm glad to see that my instructor wasn't off his gourd:mean: , when he brought this up as the ascent standard now being recommended by NAUI. I knew that I didn't remember that from my OW or AOW class. He informed me of this pocedure during Nitrox then I found more info on it here on the board.