Varying Permeability Model

Varying Permeability Model (VPM) is a decompression model used in the field of underwater diving. It was developed by David Yount and his colleagues in the late 20th century. The model is based on the concept that the body's tissues are made up of tiny, bubble-like structures that change their permeability based on the pressure they are subjected to.

History

The Varying Permeability Model was first proposed by David Yount and his team at the University of Hawaii in the 1980s. The model was a significant departure from the traditional Haldane decompression model, which assumed that the body's tissues were completely saturated with inert gas.

Principles

The VPM is based on the idea that the body's tissues contain microscopic, bubble-like structures known as micronuclei. These micronuclei are filled with gas and their permeability changes based on the pressure they are subjected to. When a diver descends, the pressure increases and the micronuclei compress, reducing their permeability and trapping the gas inside. As the diver ascends and the pressure decreases, the micronuclei expand and become more permeable, allowing the trapped gas to escape.

Applications

The Varying Permeability Model has been used to develop decompression algorithms for dive computers. These algorithms help divers plan their ascents to avoid decompression sickness, a potentially life-threatening condition caused by the formation of gas bubbles in the body's tissues.

Criticisms

While the VPM has been widely adopted in the diving community, it has also faced criticism. Some researchers argue that the model oversimplifies the complex processes involved in decompression. Others point out that the model's predictions do not always match empirical observations.

See also

• Decompression (diving)
• Decompression sickness
• Dive computer
• Haldane's decompression model