Varying Permeability Model

The Varying Permeability Model (VPM) is a modern decompression model that tries to minimize the formation of micro gas bubbles in body tissue when diving through mathematical simulation . The model was developed in the late 1990s.

It is believed that micro gas bubbles are the precursor to large bubbles . The model induces earlier or deeper decompression stops than the “classic” algorithms (e.g. Haldane / Bühlmann method ) in order to limit the formation of the bubbles in advance. When the ambient pressure falls, the body tissue becomes oversaturated with inert gas . Micro gas bubbles are created and enlarged and can become lodged in various places in the body. This can ultimately lead to decompression sickness .

The classic models ( Haldane , Bühlmann etc.), on the other hand, assume that the microbubbles are present during the ascent and only try to keep their effects as low as possible so that decompression sickness does not occur.