Modelling and Measurement of Bubbles in Decompression Sickness.

Abstract

Decompression Sickness (DCS), also known as ‘the bends’, is a recognized problem for SCUBA divers and is a danger for anyone undertaking decompression. The condition arises because gas which has collected in solution in the body is released in the form of bubbles when the ambient pressure falls. Bubbles can form throughout the body, causing a wide range of symptoms, and have been observed both stationary in various body tissues and moving in the blood. Although bubbles are known to be the cause of DCS, their production and behaviour is still not well understood. In this work the problem of bubble formation is examined in two complementary ways: firstly by automating the predominant method for the measurement of bubbles in the blood. A bubble detection algorithm is derived which offers quantitative information about the occurrence of individual bubbles in the blood based on Doppler ultrasonic measurements. However, since only limited information about bubbles can be extracted by such a technique, mathematical modelling is then used to describe the formation of bubbles in the body. A model is presented for the growth of bubbles in the vasculature from crevice shaped nuclei. Since the precise form of vasculature nuclei is not known, the effect of nucleus geometry on bubble behaviour is explored. The behaviour of a bubble which breaks away from the nucleation site is also examined and finally the relationship between bubbles forming in the blood and those forming stationary in the tissue is modelled. The combination of quantitative measurements and physiological models as presented in this work offers a complete approach to the investigation of bubble formation in the body. Ultimately it offers a novel approach to the understanding and prevention of DCS.