Coronary autoregulation based on oxygen flow: a model of oxygen supply to coronary arteriolar smooth muscle in injury and endothelial dysfunction

A multi-layers theoretical model of a coronary arteriolar smooth muscle was developed to elucidate the role of oxygen in the control of coronary blood flow. Both oxygen transport by diffusion and local tissue metabolism were considered. Oxygen partial pressure in all layers was calculated. The model suggests that in normal conditions, oxygen partial pressure reaches its minimal value in the media, where oxygen consumption is the greatest. When the smooth muscle is injured, its metabolic demands are increased in order to heal, resulting in a P(O₂) decline. These results are in agreement with experimental results. The model also shows that increased myocardial oxygen partial pressure causes the arteriolar smooth muscle to contract in response to lack of oxygen. Decreased myocardial oxygen pressure results in expansion of the arteriole allowing greater coronary flow.