Algorithms

[O-ring]

Run decoplanner at GFLo 5 and GFHi 100 for said profile

170 20
110 1
100 1
90 1
80 1
70 1
60 1
50 1
40 1
30 2
20 4
10 9
0

Drop the 20’ stop and do the 10’ stop at 20’

170 20
110 1
100 1
90 1
80 1
70 1
60 1
50 1
40 1
30 2
20 9
0

then after 20 at the
bottom, ascent at 30 fpm, consciously stopping every ten feet to achieve
this, then stop at 120-80 for 30 seconds each.

170 20
120 :30
110 :30
100 :30
90 :30
80 :30
70 1
60 1
50 1
40 1
30 2
20 9
0

At 70, the gas switch, I would do 3 minutes to get the full effect of the switch. See the post that talks about circulation time.
The 3 minutes each at 60,50,40
5 at30
8 at 20
ascend to 0 in 3 minutes

170 20
120 :30
110 :30
100 :30
90 :30
80 :30
70 3
60 3
50 3
40 3
30 5
20 8
0 3 minutes to surface

Runtime = approx. 50:30.. plus ascent from 170-120 = 50' @ 30 fpm = roughly 1.5 minutes = 52 mins?

Getting closer...but why modify it this much?

 

[Doppler]

A couple of points that have been raised here... worth talking about although slightly off topic for the poll

Spiking the O2 on gas switches... something we have found very effective using V-planner for mix dives in Great Lakes conditions and one of the user editable variables in the program set-up. Setting a rest on gas switches for 4 minutes above 100 fsw (the switch at 70 feet for instance) and for 3 minutes below 100 fsw that is. Spiking the oxygen in this way seems to have a beneficial effect (purely subjective observation) and in theory manages the vacant partial pressure opportunites in the most efficient way.

Setting gradient factors in Decoplanner to 5 and 100% trying to emulate a schedule posted by GI. Couple of things here in fact. Firstly, Erik did some stella work modifying Dr. Buhlmann's work to follow the deep stop imperative, and by whittling at the MValue presets and getting them away from default values, it's possible to get a profile that's very dissimilar to the "standard" one... in fact it follows quite closely -- especially in short exposures to the 200 foot range on standard mixes -- the profiles kicked out by bubble model algorithms....

It just seems more logical to me to use the bubble model algorithm in the first place... My bias is showing and I don't want to prejudice the poll, but I have a strong sense that the bubble theory with its premise "There are bubbles in the blood, let's deal with them, here, deep, now" models more closely what might seem to actually happen in the diver's body... rather than making radical changes to a dated premise to make it behave in a similar way. And I say this with regrets since Buhlmann is one of the unsung heroes of modern diving.

20 foot stops and ascent times... I have not read the posting that people are quoting from George, but unless he has radically changed his mind over the past couple of years, when I last talked to him, we sort of agreed that long 20 foot stops on oxygen where unnecessary and presented the potential for nasty outcomes. It would be better to deal with the offgassing necessities deeper and then spend the shortest time possible on O2 then ascent gently and get out of the water... any further oxygen therapy can take place in comfort on the surface.

OK that said... trying to emulate his profiles with the copy of decoplanner you bought from EE will likely not work. To begin with, he isn't using it. Also, what sort of profiles is he talking about? Does he specifically cite a depth, time and gas mixes? Perhaps his statement has been taken slightly out of context and he is making a general statement... the jist of which is "Don't spend ages at 20 feet."

The long 20 foot stops are a simple hang-over from earlier interpretations of decompression theory that "fixed" the massive bubbling picked up by rushing or ignoring the need for slow acsent through the deep part of the water column. This 20-foot oxygen therapy still did not fix everything and we had a whole generation of divers who were told that "Silent bubbles are OK" Bull****... silent bubbles mean you have sub-clinical decopression. Your schedule was wrong. What they were telling us is change your thinking! We only started to listen recently.

DD

 

[Ari]

Looks like it provides a little more margin for error, especially for repetitive dive series.

Ari

 

[wb416]

Doppler once bubbled...
[snip]

20 foot stops and ascent times... I have not read the posting that people are quoting from George, but unless he has radically changed his mind over the past couple of years, when I last talked to him, we sort of agreed that long 20 foot stops on oxygen where unnecessary and presented the potential for nasty outcomes. It would be better to deal with the offgassing necessities deeper and then spend the shortest time possible on O2 then ascent gently and get out of the water... any further oxygen therapy can take place in comfort on the surface.
[snip]

DD

Doppler,
I think the concept that some are working through here (how GI3 manipulates "the plan") is summarized in part of an address that he gave to a group in California May 2002.

He basically summarized what you've presented in regards to maximumizing the "Oxygen Window" and the stops closest to the gas switches. He seems to be "massaging" time away from stops that have the lowest benefit to those with the highest pPO2. However, he notates that on the stop just prior to a gas switch he drops back to back gas to "buffer" his system against the higher pPO2 at the switch, and also allow him to sit there longer, maximizing the inert gas/O2 gradient.

Deco, Deep Stops, O2 Window

To recap, it sounds like based upon a May 2002 presentation that GI3 is still espousing a philosophy similar to one that he talked with you about, which seems to be "... deal with the bubbles in their infancy rather than attempting to treat the effects of them at later stops..."

Since I'm still trying to get a "firm" grasp on all these concepts myself, feel free to redirect or correct any statements I've made.

wb

 

[MikeFerrara]

Doppler once bubbled...

OK that said... trying to emulate his profiles with the copy of decoplanner you bought from EE will likely not work. To begin with, he isn't using it. Also, what sort of profiles is he talking about? Does he specifically cite a depth, time and gas mixes? Perhaps his statement has been taken slightly out of context and he is making a general statement... the jist of which is "Don't spend ages at 20 feet."

DD

I have been trying to emulate GI's profile using the procedures he outlines in his articles not with any software. I haven't been able to get close and am wondering what I am missing.

 

[Doppler]

cwb once bubbled...


SNIP....

He basically summarized what you've presented in regards to maximumizing the "Oxygen Window" and the stops closest to the gas switches. He seems to be "massaging" time away from stops that have the lowest benefit to those with the highest pPO2. However, he notates that on the stop just prior to a gas switch he drops back to back gas to "buffer" his system against the higher pPO2 at the switch, and also allow him to sit there longer, maximizing the inert gas/O2 gradient.

...SNIP
wb

Hey there CWB (i know who you are!!!) Thanks for providing the link... yes, essentially that's it. The major difference between the 'common' bubble model aproach and George's is the dropping of the po2 immediately before the o2 spike. He has stated that this actually accelerates the inert gas outwash... not sure if he cites any studies or not or if he gives some physiological reason... my sense is that if it works it might have to do with surfactant replenishment and vasodilation... but that's a whole other issue and my strong suit -- as you know -- is physics not biology... any other thoughts on that anyone?

I think we also have to remember something important when trying to emulate a profile that works for someone else... at the bleeding edge of any technique or technology, it's easy to **** up. George and any experienced decompression diver knows how to listen to waht their body tells them about the profile they just ran... you get a sense of how close to the edge you got, and if you are sensible know what factors to note and take into account for next time. Decompression algorithms try to model what goes on... but the science is suspect (well, the math actually). A lot of it is art and alchemy.

DD

 

[O-ring]

I think we also have to remember something important when trying to emulate a profile that works for someone else... at the bleeding edge of any technique or technology, it's easy to **** up. George and any experienced decompression diver knows how to listen to waht their body tells them about the profile they just ran... you get a sense of how close to the edge you got, and if you are sensible know what factors to note and take into account for next time. Decompression algorithms try to model what goes on... but the science is suspect (well, the math actually). A lot of it is art and alchemy.

We were totally doing this as an exercise and personally I would never do any of the stuff in this thread. It was fun playing around with it though..

 

[MikeFerrara]

O-ring once bubbled...

We were totally doing this as an exercise and personally I would never do any of the stuff in this thread. It was fun playing around with it though..

Agreed. I am just trying to use GI's outlined procedure to see if I can duplicate the profile on paper (I can't). When I dive I cut tables.

 

[Richeod]

Mike,

The reason you and the others can't duplicate the profile that GI gave is because you're looking at it from the wrong angle. It is not a modified dissolved gas or bubble model profile. It is designed from scratch.
This is an early profile using what GUE has come to call Ratio Deco. This is the famous "deco on the fly" that so many people talk about. It has since evolved to a very easy to understand and even easier to implement system.

Using 21/35 and 50% (close enough to the example) at 170' for 20 minutes I get this profile.

130' 1 minute
120' 1 minute
110' 1 minute
100' 1 minute
90' 1 minute
80' 1 minute
70' 3 minutes
60' 3 minutes
50' 3 minutes
40' 3 minutes
30' 3 minutes
20' 10 minutes
10' 5 minutes

As you can see it is very close to what GI wrote. It took me about 30 seconds to come up with it. Even better is that it works very well.

Hope this sheds a little light on things.

P.S. Please don't ask me how it's done. If you really want to know Andrew G. offers a great class called Tech 1 that covers this and much more.

 

[O-ring]

Not worth the effort..