Oxygen transport: interrelationship between arterial pressure regulation and blood flow autoregulation

An oxygen transport model was used to study the effects of blood flow autoregulation and arterial pressure regulation on tissue oxygen delivery. At low to moderate levels of oxygen consumption, autoregulatory increases in blood flow act in conjunction with increased tissue diffusing capacity to maintain oxygen delivery as oxygen demand becomes increased. However, an increase in the arterial pressure becomes necessary to augment oxygen delivery at higher levels of oxygen usage. At exercise levels approaching the "maximum aerobic oxygen consumption' rate, arterial pressure regulation appears to be as important as autoregulation for maintaining delivery of oxygen to the tissues. The total negative feedback gain for autoregulatory control of tissue oxygenation varies with the rate of tissue oxygen uptake and is almost 2.0 at the maximum aerobic oxygen consumption rate. Furthermore, the feedback gain is only slightly affected by changes in the mean arterial pressure that occur normally during strenuous exercise, which is indicative of the complementary relationship between these two important control mechanisms.