A dynamic two-phase model for vascular bubble formation during decompression of divers.

Accumulated inert gas during a dive and subsequent reduction of ambient pressure may lead to formation of gas bubbles, which is the initial cause of decompression sickness (DCS). Decompression procedures are used to get divers safely up from depth, and traditionally, the algorithms are evaluated against clinical symptoms of DCS. However, this approach has several weaknesses. The symptomatology of DCS is very diffuse and there are ethical concerns evaluating procedures through provoking DCS on the test subjects. In recent decades ultrasonic Doppler and imaging to detect venous gas emboli (VGE) have been used as additional tools to evaluate decompression procedures. A statistical correlation between VGE and DCS has been shown and the method is more sensitive than clinical manifestation. This paper suggests a dynamic mathematical model for VGE. We have used a physiological approach in the model derivation with VGE as a measurable endpoint. We propose that the underlying physiological and physical mechanisms of the model can be better validated with such an objective quantitative measurement method. Two simulation examples are given to illustrate the properties of the model and why there is a potential of improving the consistency of controlling bubble formation, and consequently, the risk of getting DCS.