FUNDAMENTAL PRINCIPLES IN THE ADJUSTMENT REACTIONS OF THE ORGANISM TO ANOXIA

Abstract

Adjustment reactions to anoxia were studied in humans and animals with emphasis on respiration and circulation. With decreasing O2 conc, in the inhaled air, both respiratory vol. and blood pressure increase progressively. The blood pressure response is inversely related to the respiratory response. The blood pressure rise to a given degree of anoxia is markedly increased when the blood flow through the brain is diminished by temporarily clamping either the carotid or the vertebral arteries. The occlusion of the former is far more effective than that of the latter. Anemia of the medulla induced by increased intracranial pressure causes a greater increase in blood pressure in anoxia than under control conditions. General anemia induced by progressive bleeding increases blood pressure and respiratory response to anoxia. The addition of CO2 makes anoxia a more powerful stimulant of the sympathetico-adrenal system than is anoxia per se. The fundamental observation that the vasomotor center is excited by anoxia while other cerebro-spinal functions, except those involving the respiratory apparatus are depressed, is probably due to the fact that the sensitivity of autonomic centers to anoxia is considerably less than that of somatic centers. This may cause autonomic centers to react with signs of marked increased activity while somatic centers are depressed. This interpretation is supported by expts. in which various autonomic and somatic functions are studied under the influence of anoxia.