Whats Wrong with VPM-B

[DwayneJ]

We see the world differently. We think that there are some people who like VPM-B and some people who like GF.

We spend a lot of time and money going to scientific conferences on decompression. We listen to what the scientists have to say. And more importantly, we listen to the discussions to get a feel for beliefs that have consensus and those that are contentious. I think I can say with some certainty that the superiority of bubble models is not a widely held view in the research community.

If you want to know what is really going on, I suggest that you ignore the advocates of any algorithm and find out what the science is. Join the UHMS and read the semi-monthly "Undersea and Hyperbaric Medicine Journal."

Use the Rubicon Foundation website to search for the data.

Do anything but make your decompression decisions based on the opinions of people who are trying to get you to believe in the one true algorithm.

We believe that there is insufficient evidence to say for sure whether GF or VPMB is a better algorithm. Clearly people are using both algorithms and completing dives successfully.

If you think we are just trying to support GF, we recently hired one of the mathematicians that was heavily involved in VPM in the early days, and we will be releasing the Shearwater take on VPMB in our products within the next few months. We weren't planning on announcing it quite yet, but this seems like an appropriate time.

Bruce

Congratulations on the announcement and and thanks for the update.

Regards Dwayne

 

[Kern]

Excellent post Bruce.

Many people are using the various common algorithms and are completing dives safely. While it's not quite like the Ford versus Chevy debate, having the option to choose as a consumer is very nice.

-Doug
Liquivision Marketing & Sales Manager

Exactly, so when are you announcing VPM B for the Xeo. :blinking:

 

[DwayneJ]

Exactly, so when are you announcing VPM B for the Xeo. :blinking:

I second that.

Dwayne

 

[rjack321]

I second that.

Dwayne

What you're not going with the Uemis? They've got a fancy temperature and workload compensating implementation of ZHL-8 with up to 3 nitrox mixes!

 

[rossh]

We see the world differently. We think that there are some people who like VPM-B and some people who like GF.

We spend a lot of time and money going to scientific conferences on decompression. We listen to what the scientists have to say. And more importantly, we listen to the discussions to get a feel for beliefs that have consensus and those that are contentious. I think I can say with some certainty that the superiority of bubble models is not a widely held view in the research community.

If you want to know what is really going on, I suggest that you ignore the advocates of any algorithm and find out what the science is. Join the UHMS and read the semi-monthly "Undersea and Hyperbaric Medicine Journal."

Use the Rubicon Foundation website to search for the data.

Do anything but make your decompression decisions based on the opinions of people who are trying to get you to believe in the one true algorithm.

We believe that there is insufficient evidence to say for sure whether GF or VPMB is a better algorithm. Clearly people are using both algorithms and completing dives successfully.

If you think we are just trying to support GF, we recently hired one of the mathematicians that was heavily involved in VPM in the early days, and we will be releasing the Shearwater take on VPMB in our products within the next few months. We weren't planning on announcing it quite yet, but this seems like an appropriate time.

Bruce

Hi Bruce. Sorry I have to post a reply to this.

Lets not forget that VPM is also the product of science and research. You can review the VPM references and VPM history.

GF is not a model. GF is only a mechanism to morph a model into something else. You could apply GF to anything - not just ZHL. However, the real use of GF today is to make deep stop type plans. i.e. to copy the attributes of the bubble model.

Divers today use all kinds of deep stop systems - VPM ,RGBM, Radio Deco, VGM, Pyle stops, and more. Anyone undergoing tech training will be taught one of these or similar. Almost every tech training agency uses a deep stop model or system in the course materials. Deep stop systems are in use by most divers everywhere, and the DCS rate around the world gets lower every year - read the statistics.

I don't accept this double standard with GF. Implying that because GF morphs ZHL, some how this give GF any more authenticity. GF was made for the sole purpose to change ZHL into producing very different plans. If you use GF then your also in unproven areas of the dive profile spectrum.

In summary, no one follows the scientifically tested, approved models and methods (ZHL, Navy tables, etc). These have long since been dropped as too risky. Instead divers now favor anecdotal evidence supporting deeper stop / bubble systems. Your part of this transition too Bruce.


I starting delivering the first available VPM Windows program in 2001, with some criticism at the time. Now almost 10 years later, its seems the world has accepted the bubble model attributes and the deep stop style of planning.


Regards

 

[Slamfire]

i pick whichever one is shorter. is that bad?

Let's see:

Variable Permeability Model
Buhlmann ZHL16B Gradient Factors
Reduced Gradient Bubble Model
Ratio Deco

Conclusion - Ratio Deco is your choice, it is the shorter name. All others are too long...

 

[rjack321]

Let's see:

Variable Permeability Model
Buhlmann ZHL16B Gradient Factors
Reduced Gradient Bubble Model
Ratio Deco

Conclusion - Ratio Deco is your choice, it is the shorter name. All others are too long...

ROFL

 

[Shearwater]

Let's see:

Variable Permeability Model
Buhlmann ZHL16B Gradient Factors
Reduced Gradient Bubble Model
Ratio Deco

Conclusion - Ratio Deco is your choice, it is the shorter name. All others are too long...

LOL. Finally, a worthwhile post on this thread.

Bruce

 

[memorex77]

Just don't forget that all of the algorithms are MODELS of a very very complex system - the human body! As the word "model" implies, there are certain assumptions, i.e. simplifications of a real system. None of the models considers major factors like body fat, hydration level, PFO, age to name a few. And these are just the obvious simplifications!

Whatever tweak anybody does to the models, it may or may not improve the situation and the risk for DCS. In the end you can only try it out yourself for your own body, age, patience in decompression, you get the picture..

When ZHL-16 has been sold in millions of dive computers and the press is not full of DCS or fatalities, it can't be that bad. The introduction of GF to simulate deep stops makes sense to me, and when the GF profile shows similarities to VPM it's even better because if proves that very different models yield similar results. Can't be too bad then, either model.

 

[DwayneJ]

What you're not going with the Uemis? They've got a fancy temperature and workload compensating implementation of ZHL-8 with up to 3 nitrox mixes!

I need a rugged looking computer to "complete" my technical dive look. Uemis is way to pretty for me with that slim line case and fancy OLED graphics. An OLED screen with big chunky numbers and chunky case is ideal for me.:cool2:

Seriously, I did hear from my buddy/instructor who uses the Uemis and there are supposed to be software additions to the Uemis coming soon.