Technical discussion on VPM

Robert C. Helling helling at
Tue Mar 4 23:09:01 PST 2014

On 04 Mar 2014, at 19:50, Gopichand Paturi <gopichandpaturi at> wrote:

Hi Gopichand,

> Well I would like to tell you my progress.
> First thing first let me tell you what I am familiarizing with.

very good, you have done a lot of reading.

> I am now first familiarizing myself with the "science part of decompression"
> My plan is that I will complete science part and later I want to involve myself in Math part of it(with your help). Lastly I will familiarize deco.c code for bulhmann to get a grip of the problem.

From my perspective as a theoretical physicist, there is not really a distinction between “science” and “math”, but whatever works.

Regarding the gradient factor part of the code: The commit message at that time contained an extended discussion (including a mathematica notebook) how to obtain those formulas. Use git blame and the mailing list archive.

> I familiarized myself with the following since last few days
> 1. I learnt about the problems involved in diving.
> 2. Came to know the role of pressure in diving. The way ambient pressures               operate,in the water and their effect on lungs.
> 3. I went through Henry's law, later learnt about units involved in the calculations       in dealing with partial pressures like ATA  etc.

OK ok.
> 4. I came to know about Oxygen problems like Hypoxia,Oxygen Toxicity,CNS and     Nitrogen's narcosis. By this I meant I also learnt why and when they occur.

In a first round, you can safely ignore everything related to oxygen as this gas plays no direct role in decompression/decompression sickness.

> 5. I involved myself for quite sometime in Decompression sickness and                      Decompression...And how to avoid it like planned ascent etc.
> 6. I also came across gas mixtures involved in decompression like                           Trimix ,Heliox, Nitrox.
> 7. Also I came across microbubbles,bubbles & why they expand in the           solution of blood etc.
> Currently I am going through Bulhmann Algorithm....which hopefully I would complete in a day or two. 
> Well I am not clear about one thing ...Is it past patterns and experiences that drive decompression algorithms...or do we have explicit theory that involves perfect calcualtions to form the decompression tables?

AS others wrote before: This is not an exact science, more  a summary of what seems to work (in both controlled experiments both with tissue, animals and humans) as well as data derived from analyzing many real world dives w.r.t. their outcome regarding decompression sickness.

In any case, the whole market of decompression models is not supposed to be deterministic, there are far too many factors beyond our control that are involved. The only thing one can hope for is to reduce the probability of something sever happening to acceptable levels (I guess one accident per 10000 dives is generally accepted).


Robert C. Helling     Elite Master Course Theoretical and Mathematical Physics  
                      Scientific Coordinator                                   
                      Ludwig Maximilians Universitaet Muenchen, Dept. Physik    
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