Cerebral,Head and Body Flow of Blood During Periodic Ventilation.

Abstract

Periodic ventilation was produced in dogs under morphine-ure-thane anesthesia by (a) increased intracranial tension and (b) blocking of cerebral arteries. Practically complete control of head flow was obtained by ligating the vertebral arteries, and anterior spinal arteries and small arterioles of the cord, all in the region of the second cervical vertebra. All muscles at this level were severed. The vagi were left intact and one carotid was used for volume flow measurements. Blood volume flow changes were followed in the carotid and femoral arteries by the thermo-electric method (Gesell and Bronk. 1 The external jugular, vertebral, and femoral venous return was measured by the enclosed drop method; the submaxillary vein by the external drop. Blood pressure, ventilation, oxygen consumption, and time were simultaneously registered with the blood volume flow changes.

Two types of respiration were obtained. Type 1 gave typical symmetrical Traube Herring blood pressure waves whose frequency was that of the respiratory waves. Apneas were either short (2 seconds) or lacking; respiration in other characteristics was quite normal. The depth of respiration decreased as the carotid flow increased, sometimes to the extent of apnea; as the flow decreased to a minimum, respiratory depth increased to a maximum. The respiratory depth again decreased as the flow increased. Type 2 was characterized by very pronounced blood pressure changes which were not typical Traube Herring waves. Apneas occurred. An apnea of 123 seconds was obtained in one animal during periodic breathing. The respiratory groups usually begin during some phase of the decreased flow or they may begin as late as the very end of decreased flow. Increasing respiratory movements may or may not carry on into the period of increasing blood flow.