Regional control of cerebral vascular reactivity and oxygen supply in man

Gold electrodes implanted for treatment of psychiatric disorders and intractable epilepsy were used to measure the local oxygen availability (O 2a) in the intact brain. Relative measurement of local blood flow was obtained from micro-thermistors implanted with the electrodes. Recordings were taken during hyperpnoea, hypercapnia, hypoxia and breathing 100% oxygen. Changes of O 2a and blood flow were observed during visual and electrical stimulation, changes of posture and heart irregularities. Results are compatible with a regional auto-regulation of local cerebral oxygenation. It is suggested that the Bohr shift of the oxyhaemoglobin dissociation curve by metabolic and arterial CO 2 determines the cerebral tissue oxygenation during short-lived changes of metabolic rate and respiratory variations.