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Simulation of gas bubble growth and dissolution in human tissues during dives and recompression.

BACKGROUND
As is known, there are many cases when symptoms of decompression sickness (DCS) in divers appear extremely late (> 15 h after completion of diving) and there is much evidence for unsuccessful treatment of DCS by means of recompression. In this study, we have tried to gain insight into the roots of these phenomena.


METHODS
Using the mathematical model of extravascular gas bubble dynamics, we have analyzed the time history of such bubbles under typical air dives and recompression procedures used for DCS treatment.


RESULTS
If the parameters defining the bubble dynamics remained invariable, the bubbles formed in different body tissues would reach their maximal sizes within the well-known latency time range for DCS onset, and later these bubbles would dissolve completely during standard recompression procedures. Actually, the parameters defining the processes of bubble growth and dissolution vary with time.


CONCLUSIONS
The symptoms of DCS that arise with abnormal latency may be induced by bubbles that grow a very long time in some tissues when the rate of nitrogen washout from them is reduced significantly due to vascular bubbles blocking the microcirculation. An abnormal latency of DCS onset may also appear when the negative effects of the initially asymptomatic bubbles are detected during the very slow process of their dissolution. The failure of recompression to resolve this DCS probably happens when the previously formed bubbles are large and located in tissues with less permeability so that they dissolve very slowly.