Disturbances of Gas Metabolism in Patients with Occlusive Cerebrovascular Disease

Abstract

The physiological details of brain circulation and gas metabolism have been widely studied both in experimental animals and men; the results of those investigations have been exhaustively reviewed. Considerably less work has been devoted to the investigation of gas metabolism of the brain tissue and of lung gas exchange in the conditions of cerebrovascular disease. Nevertheless, the general changes in lung ventilation, in cerebral blood flow and, accordingly, in cerebral oxygen metabolism, which take place in patients with occlusive cerebrovascular disease, have been determined rather well. This paper is a review of some of the studies performed at Tartu State University on the pulmonary ventilation, general and cerebral gas exchange in patients with occlusive cerbrovascular disease. That equilibrium is disturbed when brain infarction develops. In cases with secondary involvement of the upper brain stem a marked central neurogenic hyperventilation occurs. Severe respiratory hypocapnia follows which in its turn causes secondary restriction of the brain oxygen supply. Both arterial hypoxemia and hypocapnia are in close correlation with mortality and most of the stroke patients with an unfavorable outcome of the disease “breathe themselves to death.” Timely surgical restoration of the blood flow via the occluded artery normalizes the brain gas metabolism. The inhalation of the gas mixture containing 7 % CO 2 permits temporary normalization of cerebral gas metabolism, but most likely only in the unaffected region of the brain.