Abstract
Periodic fluctuation or intermittency of blood cell velocity in the capillary bed has been observed by many investigators in the resting skeletal muscle, mesentery and other tissues. The Purpose of this study is to elucidate the effect of such intermittent capillary flow on O2 transport in the skeletal muscle by dynamic computer simulation.
In this simulation, capillary channels are assumed to be uniformly distributed in parallel along the muscle fiber. Intermittent capillary flow is simulated by revolving the open capillary in every group of four adjacently located capillaries, so that in each of 4 phases of the same duration, the tissue is supplied with oxygen by the different capillary corresponding to the phase respectively.From this model we could formulate partial differential equations on both O2 transport by the capillary blood flow and O2 diffusion into the tissue with simple boundary conditions, and numerically solve them by digital computer under various conditions of intercapillary distance, O2 consumption, etc.
By comparing the tissue pO2 distributions under intermittent flow with those under steady flow, it has been revealed that the tissue pO2 at the venous end of the intermittent model, particularly at the tissue located farthest from the open capillary, was higher than that of the steady one. This smoothing effect of tissue pO2 by intermittent capillary flow was increased by increasing O2 consumption and/or by decreasing capillary density in the tissue. From these results it was concluded that the intermittent flow is an effective means of supplying O2 to the tissue with smaller flow rate at rest, because it keeps the tissue pO2 distribution uniform around the venous end by raising the pO2 value at the most poorly supplied corner under steady flow.
