The effect of variation in perfusion pressure on the capillary blood flow (microflow) in the cerebral cortex of the isolated cat's head preparation.

The results of the present experiments show that capillary blood flow in the cerebral cortex fluctuates, whether the cat's head is supplied by the animal's intact circulation or by an artificial circulation system. These variations in blood flow last about 5 to 15 min and range from about 10% below to 10% above the mean. When the perfusion pressure is gradually reduced from 140 mmHg to 60 mmHg, the cortical microflow and the electrical activity of the brain remain almost constant. However, a reduction in perfusion pressure of this magnitude causes a 75% fall in total blood flow through the isolated head.