A computational study of the effect of capillary network anastomoses and tortuosity on oxygen transport

The objective of this study was to investigate the effects of capillary net work anastomoses and tortuosity on oxygen transport in skeletal muscle, as well as the importance of muscle fibers in determining the arrangement of p arallel capillaries. Countercurrent flow and random capillary blockage (e.g . by white blood cells) were also studied. A general computational model wa s constructed to simulate oxygen transport from a network of blood vessels within a rectangular volume of tissue. A geometric model of the capillary n etwork structure, based on hexagonally packed muscle fibers, was constructe d to produce networks of straight unbranched capillaries, capillaries with anastomoses, and capillaries with tortuosity, in order to examine the effec ts of these geometric properties. Quantities examined included the tissue o xygen tension and the capillary oxyhemoglobin saturation. The computational model included a two-phase simulation of blood flow. Appropriate parameter s were chosen for working hamster cheek-pouch retractor muscle. Our calcula tions showed that the muscle-fiber geometry was important in reducing oxyge n transport heterogeneity, as was countercurrent how. Tortuosity was found to increase tissue oxygenation, especially when combined with anastomoses. In the absence of tortuosity, anastomoses had little effect on oxygen trans port under normal conditions, but significantly improved transport when ves sel blockages were present. (C) 2000 Academic Press.