A New Approach to Diving Ascents 

Over the past 10 years, sport decompression divers have almost uniformly adopted ascent procedures that start decompression stops much deeper than conventional tables and diving computers recommend. In the field, deep stops were originally set through ad-hoc modifications of conventional tables, using using techniques described by Richard Pyle (Pyle-stops) and Erik Baker (gradient factors). These recent adaptations of decompression procedures based on field experience emphasize the generation of personalized tables, driven by a bottom timer and depth gauge rather than a wrist decompression computer.

The VPM, or so-called Hawaiian "Tiny Bubble" model is a first-principles decompression model that was developed by researchers at the University of Hawaii that naturally incorporates deep stops into ascent profiles. The VPM decompression method was calibrated to produce ascent times comparable to the US Navy diving tables --and are accelerated from Bühlmann-Keller based computations.
 

Open Source Code VPM Bubble Model Programs 

In the early 1990s, I developed and used BASIC language decompression programs,  based on successive extensions of Yount and Hoffman's VPM algorithm, for air, nitrox, and trimix diving (Reference 1). I was motivated by the potential of the new algorithm to reduce ascent times and to decrease the bubbling that we routinely observed by Doppler probes following long decompressions based on shallow-stop models. Examples of ascent schedules, calculated by the VPM programs that are available on this site, are shown on the Santa Barbara Alps and the VPM Trimix pages. 

Since my presentation Bubble Decompression Strategies  at aquaCorps'  tek95 diving technology conference, I've given out open-source decompression programs based on the VPM to hundreds diving programmers world-wide. My objective is to make this non-traditional algorithm as transparent as possible, while supporting the efforts of professional and fellow amateur programmers who continue to develop and extend this decompression model's usability and applicability to real-world diving scenarios.  

During 1999 and 2000, I had the privilege of collaborating with the originator of the VPM, Prof. David Yount, as well as Erik Baker, who closely ties his diving experience to decompression algorithm development. An essential principle of our collaborations was that our work should be open in algorithms and code --so that those on the decompression line could fully access (and hopefully understand) our models and assumptions. I therefore encourage divers to delve into the details, and applaud those programmers who continue the VPM tradition of making source code and deco tools transparent and freely available.

If you don't program, then I encourage you to go to the Links page and download the VPM decompression programs with graphical interfaces. If you are interested in the VPM algorithm's details, you can download a number of open source programs from  VPM Decompression Site .

Rob Murray runs a mailing list concerning decompression computation and practice. If you are interested in subscribing, then drop him a line and tell him that the VPM web site sent you!