EFFECTS OF HYPOXIC HYPOXIA AND CARBON MONOXIDE-INDUCED HYPOXIA ON THE CARDIOVASCULAR SYSTEM AND REGIONAL BLOOD FLOW OF THE ANESTHETIZED CAT

The purpose of this study was to investigate the potential responses of the cardiovascular system and regional blood flow to hypoxic hypoxia (BB) and to carbon monoxide (CO)-induced hypoxia (COH). Ten anesthetized cats were studied under two nonnoxic (control: CONT) and two hypoxic conditions. Four types of radioactive micro spheres were used to measure regional blood flow during CONT and two hypoxic conditions. During CONT the animal was ventilated with 22% 02' 5% CO2 and N2 (room air). HH was induced by ventilating the cat for 15 min with 6-8% O2, and COH by adding 0.1 % CO to room air and reducing blood oxygen content to the same level as HH. Cardiac output and contractility significantly increased (pO.05). Gastric blood flow (14±2 CONT) only increased during HH (22±4) but splenic blood flow (119±2 CONT) decreased with both HH (40±9) and COH (37±9). Regional blood flow of other segments measured showed a mixed response to HH and COH. In conclusion, it seems that: 1) systemic hypoxia would stimulate the heart to increase its output to maintain Pa and overcome the increased demand of some organs, and 2) the different responses of regional vascular beds to HH and COH may be due to various sensitivities of each organ to arterial blood oxygen tension and autonomic neuro-hormonal controls that have originated from stimulations of aortic and carotid chemoreceptors.