Effect of hyperoxia on regional blood flow after coronary occlusion in awake dogs

The effect of 100% oxygen inhalation on regional transmural myocardial blood flow following 45 s of acute total left circumflex coronary artery occlusion was studied in six awake dogs chronically instrumented with a coronary occluder and catheters in the aorta and left atrium. After inhalation of either room air or 100% oxygen for at least 30 min and following the 45-s occlusion, transmural myocardial blood flow was determined with radioactive microspheres (7-10 μm). Each dog underwent two occlusions of the left circumflex coronary artery; one during inhalation of room air and the other during 100% oxygen. During room air inhalation, mean regional myocardial blood flow to nonischemic, intermediate, and ischemic regions was 0.92 ± 0.05, 0.51 ± 0.08, and 0.10 ± 0.02 ml/min^-1/g^-1, respectively. During 100% oxygen administration, flow was significantly diminished in each region to 0.75 ± 0.04, 0.41 ± 0.07, 0.06 ± 0.01 ml/min^-1/g^-1, respectively. Transmural blood flow to each layer was uniformly reduced in all regions. These data indicate that 100% oxygen further reduces myocardial blood flow to ischemic regions.