EFFECTS OF ARTERIAL CARBON DIOXIDE TENSION AND OXYGEN SATURATION ON CEREBRAL BLOOD FLOW AUTOREGULATION IN DOGS

Abstract

ABSTRACT Effects of arterial carbon dioxide tension and oxygen saturation on cerebral blood flow autoregulation in dogs. Acta physiol. scand. 1965. 66. Suppl. 258. 27–53. ‐ Pressure‐flow relation‐ ships of the cerebral circulation under influence of variations in arterial carbon dioxide tension and oxygen saturation were studied in pentobarbital anaesthetized dogs. Cerebral blood flow was measured by recording of the γ‐ emission of radioactive krypton (Kr 85 ), which was injected into the vertebral artery. The recorded desaturation curve was resolved into two exponential phases and the fast phase was considered as representative of blood flow in the grey matter of the brain. It was demonstrated that autoregulation of flow occurred within wide pressure limits under normo‐ and hypocapnia. Auto‐regulation was less pronounced under hypercapnia and was abolished at low arterial oxygen saturation. Possible mechanisms of autoregulation of cerebral blood flow are discussed. Evidences are presented which speak against the theory that changes in the carbon dioxide tension are the main cause of this autoregulation. The results from previous studies concerning the principal effects of arterial carbon dioxide tension and oxygen saturation on cerebral blood flow were confirmed.