Cerebral blood flow autoregulation: effect of hypercapnia on cerebral tissue gas concentrations.

In clinical medicine many conditions are encountered which adversely affect the oxygenation and perfusion of the cerebral cortex. Shock, sepsis, and posttraumatic pulmonary insufficiency or adult respiratory distress syndrome are frequently encountered complications of major surgical illness. Prolonged cerebral hypoxia may result in diffuse cerebral damage while other organ systems remain viable. Cerebral oxygen consumption remains relatively constant in conditions of arterial hypoxemia but cerebral utilization of glucose rises sharply. With hypoxia moderate changes in arterialp0, do not cause significant changes in cerebral blood flow; but more severe hypoxia results in increased blood flow. Hypercapnia causes a profound increase in cerebral blood flow and markedly improves task performance of humans exposed to acute ambient hypoxia [3]. The