Varying Permeability Model

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

It is assumed that gas microbubbles are the precursor of large bubbles. The model induced earlier or deeper decompression stops than the "classic" algorithms (eg Haldane / Bühlmann method) to limit the formation of bubbles in advance. By falling ambient pressure the body tissue becomes supersaturated with inert gas. There arise and increase in size micro gas bubbles that may get stuck in various places in the body. This can ultimately lead to decompression sickness.

The classic models ( Haldane, Bühlmann, etc.) shall, however, assume that the micro gas bubbles during ascent are available, and are just trying to keep the impact as low as possible so that it does not lead to decompression sickness.

• Dive Theory