Low Alveolar Oxygen Pressure, Sodium Cyanide and the Carotid and Femoral Flow of Blood.

Abstract

Methods of study similar to those described in the preceding paper on the effects of variations in alveolar carbon dioxide were used. The administration of low oxygen by either natural or artificial ventilation elicited an increased carotid flow of blood, followed by a decrease on re-administration of room air, and a decreased femoral flow, which increased on subsequent administration of room air. Variations from this response were slightly more common than variations with the administration of carbon dioxide. An initial decrease in carotid flow, preceding the increase, and a subsequent decrease in flow below normal, on re-administration of room air, were not infrequent. Changes in flow were more abrupt, and more fluctuating, than those produced by carbon dioxide. This peculiarity, however, was frequently missing. A response to low oxygen may be identical to a response to high carbon dioxide. Intravenous injection of sodium cyanide produced a general increase in carotid flow of blood, and a decrease in femoral flow. An initial decrease in carotid flow preceded the increase. When the mean blood pressure was maintained approximately constant by artificial regulation, the same directional changes in flow obtained. The similarity of circulatory response to low oxygen and sodium cyanide suggests like chemical disturbances in and on the opposite sides of the neurone membranes of the circulatory centers involved in the regulation of circulation. The inverse relation of carotid and femoral flows suggest again that circulatory adjustments occurred in favor of the brain. Likewise, the similarity of the circulatory response to the administration of carbon dioxide on the one hand, and to the administration of low oxygen and sodium cyanide on the other, suggests common factors of control.