Figure 4.
Local vascular reflexes support maintenance of O2 delivery to tissue in the setting of progressive hypoxia. In a classic paper41, Guyton demonstrated regional autoregulation of systemic blood flow in normal dogs (following spinal anesthesia) by observing variation in blood flow during constant pressure blood perfusion of the femoral artery, while reducing the hemoglobin oxygen saturation (Hb SO2%) from 100% to 0% in the perfusing blood. (A) Stepwise reduction in Hb SO2% caused a progressive increase in blood flow through the leg. (B) These data demonstrate that autoregulation of blood flow occurs at a local level and this regulation serves to improve oxygen supply when blood oxygen content falls. In addition, effects on blood flow were replicated by injecting partially deoxygenated versus oxygenated red blood cells into the artery, demonstrating that effects could be elicited during arteriovenous transit (<1 s).
From Ross JM, Fairchild HM, Weldy J, Guyton AC. Autoregulation of blood flow by oxygen lack. Am J Physiol. 1962;202:21–24; with permission.