The Varying Permeability Model, Variable Permeability Model or VPM is an

algorithm In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific problems or to perform a computation. Algorithms are used as specifications for performing ...

that is used to calculate the

decompression stop The practice of decompression by divers comprises the planning and monitoring of the profile indicated by the algorithms or tables of the chosen decompression model, to allow asymptomatic and harmless release of excess inert gases dissolved in ...

s needed for ambient pressure

dive profile A dive profile is a description of a diver's pressure exposure over time. It may be as simple as just a depth and time pair, as in: "sixty for twenty," (a bottom time of 20 minutes at a depth of 60 feet) or as complex as a second by second grap ...

s using specified

breathing gas A breathing gas is a mixture of gaseous chemical elements and compounds used for respiration. Air is the most common and only natural breathing gas, but other mixtures of gases, or pure oxygen, are also used in breathing equipment and enclosed ...

es. It was developed by D.E. Yount and others for use in

professional diving Professional diving is underwater diving where the divers are paid for their work. The procedures are often regulated by legislation and codes of practice as it is an inherently hazardous occupation and the diver works as a member of a team. D ...

and

recreational diving Recreational diving or sport diving is diving for the purpose of leisure and enjoyment, usually when using scuba equipment. The term "recreational diving" may also be used in contradistinction to "technical diving", a more demanding aspect of ...

. It was developed to model laboratory observations of bubble formation and growth in both inanimate and

in vivo Studies that are ''in vivo'' (Latin for "within the living"; often not italicized in English) are those in which the effects of various biological entities are tested on whole, living organisms or cells, usually animals, including humans, and ...

systems exposed to pressure. In 1986, this model was applied by researchers at the

University of Hawaii A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. Universities typically offer both undergraduate and postgraduate programs. In the United States, th ...

to calculate diving

decompression tables There are several categories of decompression equipment used to help divers decompress, which is the process required to allow divers to return to the surface safely after spending time underwater at higher ambient pressures. Decompression o ...

Theoretical basis

The VPM presumes that microscopic bubble nuclei always exist in water and tissues that contain water. Any nuclei larger than a specific "critical" size, which is related to the maximum dive depth (exposure

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...

), will grow upon decompression when the diver ascends. The VPM aims to minimize the total volume of these growing bubbles by keeping the external pressure large, and the inspired inert gas partial pressures low during decompression. The model depends on the assumptions that different sizes of bubbles exist within the body; that the larger bubbles require less reduction in pressure to begin to grow than smaller ones; and that fewer large bubbles exist than smaller ones. These are used to construct an algorithm that provides decompression schedules designed to allow the larger, growing bubbles to be eliminated before they can cause problems.

Bibliography

This bibliography list was compiled by E.B. Maiken and E.C. Baker as reference material for the V-Planner web site in 2002.

Primary Modeling Sources

* * * *

VPM Research and Development Sources

* * Kunkle, T.D. 1979. Bubble nucleation in supersaturated fluids. Univ. of Hawaii

Sea Grant The National Sea Grant College Program is a program of the National Oceanic and Atmospheric Administration (NOAA) within the U.S. Department of Commerce. It is a national network of 34 university-based Sea Grant programs involved in scientific re ...

Technical Repor
UNIHI-SEAGRANT-TR-80-01
Pp. 108. * * * * * * * * * * Yount, D.E. 1979. Multiple inert-gas bubble disease: a review of the theory. In: Lambertsen, C.J. and Bornmann, R.C. eds. . Undersea Medical Society, Bethesda, 90-125. * * * * * * * *

VPM Dive Planning Software

* V-Planner: VPM-B & VPM-B/E, VPM-B/FBO. * MultiDeco: VPM-B & VPM-B/E, VPM-B/FBO, ZHL-B, ZHL-C, GF, and GFS. * Ultimate Planner: VPM-B, VPM-B/U, VPM-B (Dec-12), VPM-B/U (Dec-12), ZHL-B, ZHL-C, ZHL-D, GF and GF/U. * DecoPlanner: VPM-B. * HLPlanner: VPM-B. * JDeco: VPM-B. * PalmVPM: VPM. * DivePlan: VPM. * Baltic Deco Planner: VPM-B. * Subsurface: VPM-B.

VPM Dive computers

* V-Planner Live: VPM-B & VPM-B/E. * MultiDeco-X1: VPM-B & VPM-B/E, VPM-B/FBO, ZHL-C, GF, and GFS. * MultiDeco-DR5: VPM-B & VPM-B/E, VPM-B/FBO, ZHL-C, GF, and GFS. * Shearwater Research Predator, Petrel, Perdix and NERD models: GF, VPM-B plus GFS. * RATIO Computers: iX3M series and iDive (Tech and Reb) series VPM-B and ZHL16-B. * TDC-3 with MultiDeco-TDC: VPM-B & VPM-B/E, VPM-B/FBO, ZHL-C, GF, and GFS. * HeinrichsWeikamp OSTC4: VPM-B

References

External links

VPM web site

{{authority control Decompression algorithms