A theoretical model for oxygen transport in skeletal muscle under conditions of high oxygen demand

Oxygen transport from capillaries to exercising skeletal muscle is studied by use of a Krogh-type cylinder model. The goal is to predict oxygen consum ption under conditions of high demand, on the basis of a consideration of t ransport processes occurring at the microvascular level. Effects of the dec line in oxygen content of blood flowing along capillaries, intravascular re sistance to oxygen diffusion, and myoglobin-facilitated diffusion are inclu ded. Parameter values are based on human skeletal muscle. The dependence of oxygen consumption on oxygen demand, perfusion, and capillary density are examined. When demand is moderate, the tissue is well oxygenated and consum ption is slightly less than demand. When demand is high, capillary oxygen c ontent declines rapidly with axial distance and radial oxygen transport is limited by diffusion resistance within the capillary and the tissue. Under these conditions, much of the tissue is hypoxic, consumption is substantial ly less than demand, and consumption is strongly dependent on capillary den sity. Predicted consumption rates are comparable with experimentally observ ed maximal rates of oxygen consumption.