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VPM model in detail
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The VPM model is the result of many years of work by dedicated individuals, researchers, dive industry staff and technical divers. The various algorithms used in the model were developed over many years, initially in research work and later in a wider group in an open source environment. All work has been subject to peer review and the final work was completed in 2000. Erik Baker and Eric Maiken were central to bringing the model to completion. They added the final revision to VPM-B in 2002, which has become the standard in common use today.
The dive profile from a VPM-B profile is a one that includes both deep stops and modest amount of time in the shallow areas. The basic concept of a bubble model is to limit and control bubble growth and bubble sizes to smaller amounts through the ascent, thereby avoiding the damaging effects of any larger bubbles.
A significant amount of diver feedback and experience has demonstrated the VPM-B model is suitable for a wide range of dive profiles. The VPM-B model produces consistent decompression plans for the entire range of dives, and accurately intercepts the NDL limits as well.
The VPM-B/E model variation is for the extreme or extra long dives and exposures. It gives a more relaxed version of a profile for dives when extra safety is prudent. With bigger dives (typically more than 100 mins deco), the profile will diverge from the standard VPM-B, and produce a profile similar to a combined or overlapped VPM-B and Haldane plan. Divers who carry out the very long and deep dives, often prefer the additional margin of safety from this combination plan concept, and the VPM-B/E generates a plan to meet this requirement.
The VPM-B/FBO model variation (Fast Bail Out) is for the use with closed circuit diving and a bail out suituation. The purpose is to help reduce the required diluent gas volume during bailout (typically a 30 to 50% reduction). A Fast Bail Out ascent will reduce the time spent at the deeper stops, and cause the decompression to expand into the shallow stops. The changed ascent shape is still calculated within the context of the VPM-B model. These ascents are aggressive and have fewer deep stops than a regular plan, but VPM-B/FBO still has more deco time than a matching raw Bulhmann plan.
Brief history of the VPM.
1974 - 1981 U of Hawaii
Series of research papers (15+) by Yount,D.E. Hoffman,D.C Kunkle,T.D. Strauss, R.H. D’Arrigo, J.S., Ingle, F.W., Yeung, C.M., and Beckman, E.L. Yeung, C.M. Paganelli, C.V., Gillary, E.W.,1982 - 1984
Research papers by Yount,D.E. Hoffman,D.C SGillary, E.W.1986
Varying Permeability Model (VPM) - Yount and Hoffman1990
Eric Maiken starts working the VPM code, and start formatting his own VPM program made with BASIC.1992
Eric Maiken starts diving the model in the 130-220ft depth range, with O2 decompression, and progressing to trimix to 250 ft.1994
Eric Maiken distributes his BASIC VPM program, to divers / researchers. Program is now multi-level and nitrox mix capable.1995
The Yount and Hoffman (1986) VPM algorithm was made freely available to programmers and researchers at the tek95 diving technology conference. Eric released his VPM program code at this time in the VBA format, with an Excel spreadsheet front end. Eric Maiken reported his experiences with non Buhlmann based deco.1997
Eric Maiken's program is now distributed in Mathematica and full trimix capable.1998
The VPM List (later named DecoList) is started by Rob Murray, to discuss and test progress in the work on the Eric Maiken's VPM model code. David Yount joins in discussions, pleased to see his research work in use.1999
VPM development progresses with David Yount, Eric Maiken, Erik Baker working on repetitive diving, and a paper for the Smithsonian conference on reverse dive profiles.2000
David Yount, UH physics and astronomy professor, dies in April at age 64.2001
Ross Hemingway (developer of the 2ZPlanner program) adapts the VPM Fortan codes by Erik Baker from its DOS console state, into a full Windows program. This is the first Windows program with VPM, and the general public has its first look and use of VPM profiles. The new program is named V-Planner and is released as a freeware in July.2002
VPM use in recreational tech diving grows. Model is adapted for use with CCR planning. Diver feedback and documented experiences grow. Initial feedback suggests the model is somewhat range bound in its profiles. Erik Baker starts work on a revision to the original model. This results in a change to the method of calculating ascent ceilings and how they are propagated through the ascent. The revision to the model is named VPM-B, and becomes the standard for VPM.2003
February: V-Planner with VPM-B released at the NAUI Deep Stop conference.2004
V-Planner and VPM/B is now widely used by tech divers in the USA & Canada, and continues to grow throughout the world.2005
VPM-B/E model option introduced.2006
Cedric Verdier sets record 201m Meg rebreather dive in Sra Keow cave in Krabi Thailand using the VPM-B/E. Three months later Cedric Verdier dives to 176m on the Yamashiro, with VPM-B/E. see trip reports.2007
Cedric Verdier on a Meg and with VPM-B/E, along with Ben Reymenants (unknown deco) on OC, do a team dive to 226m and 239m in the Sra Keow cave in Krabi Thailand. see trip reports.2008
Matt Reed, Mike Taylor, Roger Ingebo, Paul Neilson dive to 110-120m on the Princess of Orient, outside Manila Bay, Philippines (7 dives total). All divers used VPM-B and Mike used a Liquivision X1 with V-Planner Live.2009
Created the V-Planner Live online data base. Divers can upload the actual dive profiles as recorded in the Liquivision X1, into the database. The database holds 11,000 dive profiles as of Aug 09, and continues to grows by 1,000 dives a month.
See also... VPM References, Eric Maiken's VPM decompression site (bubble model explanations).
1. Gradient Factors are in now use with many Bulhmann based algorithims, including DecoPlanner.
2. ZPlanner was a wrapper around the Zplan DOS program by the late Will Smithers.