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A Model of Bubble Evolution during Decompression Based on a Monte Carlo Simulation of Inert Gas Diffusion.
Technical rept. Jun 92-Jun 93,
NAVAL MEDICAL RESEARCH INST BETHESDA MD
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Previously, a Monte Carlo simulation of inert gas diffusion in a capillary bed bad been developed at this laboratory to explore the effect of tissue heterogeneity and microvascular architecture on gas exchange under normobaric conditions. Because we needed a method of looking at gas phase dynamics during decompression in this environment, the Monte Carlo method was extended to simulate bubble growth and dissolution during decompression. The essence of our approach involves the placement of inert gas particles in a bubble-liquid module and simulating diffusion with random displacements within the module for a short, fixed time period. At the end of the time period the distribution of the particles is used to calculate the number of moles of gas inside the bubble. The new bubble volume is then calculated from the ideal gas law. We developed methods to speed up the simulation by computing distributions of displacements following many random steps so that the simulation of many steps might be made with a simple calculation. In addition, we can calculate the amount of time a particle will stay inside the bubble based on the solubility of the inert gas. We demonstrate that a bubble evolves to the expected equilibrium sine and the time course of the evolution compares favorably with that predicted by a partial differential equation model. A Monte Carlo approach is successful in simulating bubble evolution during decompression and is potentially suitable for studying the influence of tissue micro-architecture on gas phase dynamics.
APPROVED FOR PUBLIC RELEASE