COMPUTER DETERMINATION OF PERFUSION PATTERNS IN PULMONARY CAPILLARY NETWORKS

Individual pulmonary capillaries are not steadily perfused. By using i n vivo microscopy, it can readily be demonstrated that perfusion conti nually switches between capillary segments and between portions of the network within a single alveolar wall. These changes in capillary per fusion occur even when upstream pressure and flow are constant. Flow s witching between capillary segments in the absence of hemodynamic chan ges in large upstream vessels suggests that capillary perfusion patter ns could be random. To calculate the probability that perfusion patter ns could occur by chance, it is necessary to know the total number of possible perfusion patterns in a given capillary network. We developed a computer program that can determine every possible perfusion patter n for any given capillary network, and from that information we can ca lculate whether perfusion of individual segments in the network is ran dom. With the results of the computer program, we have obtained statis tical evidence that some capillary segments in a network are nonrandom ly perfused.