Difference between MB levels and Gradient Factors

[ThatDogDontHunt]

He just wants to say ScubaPro is nearly perfect. and has added nothing but irrelevant references to butress -- not prove --his point.
You two SP fanboys need to get a room.

It is tiresome when people blindly say models are not perfect, and then conclude that therefore they must be useless.

The thread started with the OP wanting to compare MB levels to GFs. It cannot be done, of course, but post #10 provided a report where someone did the best they could.

For some reason he thinks that saying something over and over will make it true.
I can only conclude that I'm wasting my time with this thread.

I believe I learned something.

I already knew that Uwatec had some sort of micro bubble adjustment in its very early models - hence the ADT added to the algorithm name. I was vaguely aware that it would "affect the algorithm" in some way. On re-read the Aladin Sport manual clearly states that the no-stop is shortened if a rapid ascent happens (no details on how much). There may be other info? There was no MB adjustment in early Aladins.

The later Smart computer information (linked above) appears to explain that changing the MB level changes the depth/number of "deep stops". This seems to imply that the Smart introduced deep stops based upon the assumption of presence of micro bubbles? These deep stops lengthen the time to surface.

From the info I found (and linked in prior posts) it appears that Buhlmann was involved in this ADT stuff. Not sure to what extent.

Seems it would be interesting to take an old Aladin on some chamber rides to see if fast ascents cause different reactions? As well as different water temps? It would take a much fancier setup than I have to also include workload effects by providing air pressure info and maybe a heart rate monitor?

 

[Wibble]

Dancing around the angels on a pinhead.

The technical diving community has coalesced around Bulhmann + GF. Consistency and reliability is more important than proprietary algorithms. Bulhmann may be just a mathematical model with no underlying physiological theories, but it works. It’s been used in many more significant dives than all the others.

It was nice to have some peace and quiet after years of bickering over bubble models and deep stops. Similarly arguing over whacky gradient factors.

 

[L13]

Bulhmann may be just a mathematical model with no underlying physiological theories, but it works.

This is inaccurate. Bulhmann IS based on underlying physiological theories. Scientific experimentation has been done to validate it. Yes, it is an approximation, it is know to be an oversimplified and incomplete model, and it is known to not perfectly match experimental data. But dismissing it as "just a mathematical model" would be like dismissing the Newtonian model of gravity because it doesn't account for relativity. For both models, if you stay well within the envelope for which it has been validated they are extremely useful.

 

[Wibble]

This is inaccurate. Bulhmann IS based on underlying physiological theories. Scientific experimentation has been done to validate it. Yes, it is an approximation, it is know to be an oversimplified and incomplete model, and it is known to not perfectly match experimental data. But dismissing it as "just a mathematical model" would be like dismissing the Newtonian model of gravity because it doesn't account for relativity. For both models, if you stay well within the envelope for which it has been validated they are extremely useful.

Please see the context; the "just a mathematical model" was in the context of the VPM, based upon bubble theories and therefore measurements. The Bulhmann model has an approximation to different rates of gas perfusion into different tissues but the numbers are a mathematical series for the 16 compartments -- you're not supposed to say that compartment 1 is blood and compartment 16 is toenails.

The point is that Bulhmann works. It matters little "how" or "why", all that really matters is it works.

 

[Rachel Iversen]

I am going to disagree with you on this one. You very graciously supplied a "chart" from some source with no money in the game so to speak.

To understand the OP's question, you need to understand what is going on with Scubapro and what their definition of what a MB in relation to their UWATEK programming actually is. And since they are not very forthright with detailed explanations , they rely heavely on their dealer network, AND no one here has even come close to explaining what the varying levels of MB's do in relation to a G2 or any of the 10 MB level settings, it is virtually impossible to make this comparision. It is in fact a "loaded" question. From the very bigining. I'm saying it is very problamatic to make a direct comparison between GF and MB in the first place. And support this with information from the internet. Although I will freely support your efforts to provide the information you have supplied, no one else bothered to really do much of anything. Problem is, it dosen't come from the manufacturer. And trying to make a comparision between 10 MB settings and high / low does not do as much as understanding what diving conservativly means in the first place. Because every time someone mentions diving conservativly on this site, they get their head taken off.

Here is the only word from the manufacturer that we have:

78 GALILEO 2 (G2) USER MANUAL

3 .8 Diving with MB levels
Microbubbles (MB) are tiny bubbles that
can build up inside a diver’s body during any
dive and normally dissipate naturally during
an ascent and on the surface after a dive.
Dives conducted within no-stop times and
the observance of decompression stops do
not prevent the formation of microbubbles
in the venous blood circulation.
Dangerous microbubbles are those
migrating into the arterial circulation. The
reasons for the migration from the venous
blood circulation to the arterial circulation
can be a many microbubbles collecting in
the lungs. SCUBAPRO has equipped the
G2 with technology to help protect divers
from these microbubbles.
With the G2, you can choose – according
to your specific needs – a MB level that
will provide a level of protection from
microbubbles. Diving with MB levels
includes additional ascent stops (level
stops); this slows the ascent process,
giving the body more time to desaturate.
This works contrary to the formation of the
microbubbles and may increase safety.
The G2 features 10 microbubble levels (L0-
L9). Level L0 corresponds to SCUBAPRO’s
well-known decompression model ZH-L16
ADT and does not require level stops due
to microbubble formation. Levels L1 to L9
offer additional protection from microbubble
formation, with level L9 offering the highest
protection.
Similar to the display of information during
decompression dives or dives within no-stop
time, the G2 displays depth and duration of
the first level stop as well as the total time
of ascent as soon as the MB no-stop time
has run out. As the MB no-stop time is
shorter than the ordinary no-stop time you
will be required to perform a stop (level stop)
sooner than a diver using level L0.
If you ignore a required level stop, the G2
will simply step down to a lower MB level.
In other words, if you choose level L8 prior
to the dive, and during the dive you ignore
the L8’s recommended stops, the G2 will
automatically adjust the setting to level L7
or lower.
3 .8 .1 Comparison of dives with MB
level L0 and MB level L9
When two G2 dive computers are used
simultaneously, with one unit set to a MB
level of L9 and the other to a MB level of
L0, the no-stop time for the L9 unit will
be shortened and more level stops will be
required before the diver has the obligation
of a decompression stop. These additional
level stops help dissipate microbubbles."




So why is Scubapro mum with what it means to dive conservativly V fully explaining what their version of MBs' are? IMO it has to do with deep stops. And the confusion this creates. If setting a G2 to the most conservative setting, promotes deep stops, considering the current political climate this will not be good for sales. If on the other hand if your diving with an undiagnosed PFO, setting your G2 to 9 could very easily save your life. These are the questions that need explaining. And to date no one has come close.

I will say one thing, Scubapro certianly dosn't hold anyones hands with detailed explanations and everyone else is real short on documentation.

And here is the link again: https://www.divetable.info/Flyer/brochure_metric.pdf

I'm goanna throw this in as well: "The human body cannot currently be mathematically modelled. Not only are individuals different because of age, fitness, pulmonary and cardiac (PFO) defects, but they also vary on a daily basis due to hydration, stress, exercise, micro-nuclei generation, and many other factors."

Thanks to: Kevin G. Variable Gradient Model: An Approach To Create More Efficient Decompressions

I'm going to dive into this a little bit because you just mentioned a point that a lot of people are hanging their hat on. (Pun intended.)

I hope you don't mind. And I'm trying something out here as well.

So taking into account the NEDU Research, I know you know about it. Your pointing out the significance of the fact that the "Decompression Total Stop Time," between the two study condition groups was the same. In essence the amount of time available to decompress was equal. And I should point out this was a fixed time set by the researchers? However in relation to the limited information regarding Micro Bubble formation and the 10 MB levels of conservatism that you can set the G2 devices to, the amount of time to decompress / reduce the formation of micro bubbles, the actual time is free to increase. Time is not constrained. Looking at the chart from the micro bubble management PDF you posted, clearly across the board the total time for any particular dive the time increases as the MB setting increases. And that this kind of cancels the deep stop V shallow stop issue? It seems that the concern about deep stops v shallow stops isn't warranted due to the idea that with an air integrated device the device will take into account the amount of air remaining (Basically Time.) and will take this all into account with the RBT. In a sense even if the G2 makes a "deeper" stop in order to absolutely limit the initial formation of micro bubbles the potential "penalty / risk of DCS" by making deep stops will be negated by the fact that total time will increase? And yes NDL bottom time will decrease but as far as micro bubble formation will be much safer? Seems that so much of this learning experience is missing "depth." Poor choice of words, perhaps. But to me it seems that many have concentrated on times and how that relates to DCS as compared with depths. I'm going to say this this way, perhaps someone can explain better: The G2 makes deep stops as you increase ( More conservatism) MB settings, but the increased overall time takes care of any perceived increase in DCS risk. So it seems that the issue of deep stops Vs shallow stops really isn't a concern for recreational divers more interested in preventing micro bubbles? If preventing micro bubbles for a number of valid reasons is of real importance to you, having MB settings is a very valuable feature. I"m an older recreational diver and this is a subject I want to learn more about, but this subject seems to digress to a deep stop Vs. shallow stop every time. This is the comment that started this whole thing off:
"REDISTRIBUTION OF DECOMPRESSION STOP TIME FROM SHALLOW TO DEEP STOPS INCREASES INCIDENCE OF DECOMPRESSION SICKNESS IN AIR DECOMPRESSION DIVES."

And this conclusion: "The practical conclusion of this study is that controlling bubble formation in fast
compartments with deep stops is unwarranted for air decompression dives." So this whole research really doesn't apply to the MB settings on the G2 in the first place? If the slower tissues are still on gassing, during the higher MB settings, the increased time on ascent will cancel everything out.

In the context of recreational dives, when and where in the context of the G2 your finite air supply is taken into account? So the conclusion of that research really doesn't apply if your concerned more about AGE than anything else? I do wish there was more information about their MB levels and how each level would apply to age, fitness, and those kinds of things?

I noticed this place and joined just because I was searching the internet, I hope this is ok here? I hope no one minds.

 

[scubadada]

From Deco for Divers, Mark Powell

"Unlike the first two models, which used 16 compartments, the newer model ZH-L8ADT uses only 8 compartments. It also includes the effects of temperature and work or breathing rate during the dive as well as taking into account microbubble formation. Unfortunately the ZH-L8ADT model is described only superficially in the latest edition of Buhlmann's book and doesn't include many details of the parameters of the model. The model was adopted by Uwatec and is the basis for their range of dive computers, as such it has been extensively dived by recreational divers around the world."

I don't know where the 16 compartment of this model came from. Body temperature and heart rate must come from the use of a chest strap. The sensitivity for breathing rate can be set very low (off?). Microbubble can be turned off. It would be interesting to know the performance of the native algorithm. Skin temperature, work load, and breathing rate make the algorithm more conservative. MB gives deep(er) stops.

I think Scubapro is realizing this is a loser and is moving toward Buhlmann ZH-L16C with GF (G2 Tek, option for HUD)

 

[BoltSnap]

with GF (G2 Tek, option for HUD)

And the new LUNA 2.0 computers that should be out Q3/Q4 this year.

 

[scubadada]

And the new LUNA 2.0 computers that should be out Q3/Q4 this year.

Thanks @BoltSnap, I forgot about the Luna 2.0, seems like it's been a long time coming. It will be their 2nd computer running ZH-L16C with GF along with their ADT algorithm.

 

[Sevenrider860]

I think Scubapro is realizing this is a loser and is moving toward Buhlmann ZH-L16C with GF (G2 Tek, option for HUD)

I would not go that far.

I think it is more likely that Scubapro is trying to capture additional sales with technical divers. The G2 is still selling very well and is only ZH-L16 ADT MB PMG. The G2 Tek is not a replacement to the G2, it allows technical divers to stay within the Scubapro system when they start moving to technical diving with offline deco planning. This might prevent a lost sale to Shearwater.

The HUD continues to support both algorithms, the Luna 2.0 computers will support both algorithms, and I believe the upcoming G3 wrist model will support both algorithms.

I see the support for ZH-L16 GF as a way to expand their current market, not to replace their existing ZH-L16 ADT MB PMG computer line which is selling very well..

 

[BoltSnap]

upcoming G3 wrist model

Is this a watch style version of the g2 Tek or something else?