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

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Abstract
The effect of 100% O2 inhalation on regional transmural myocardial blood flow following 45 s of acute total left circumflex coronary artery occlusion was studied in 6 awake dogs chronically instrumented with a coronary occluder and catheters in the aorta and left atrium. After inhalation of either room air or 100% O2 for at least 30 min and following the 45 s occlusion, transmural myocardial blood flow was determined with radioactive microspheres (7-10 .mu.m). Each dog underwent 2 occlusions of the left circumflex coronary artery; one during inhalation of room air and the other during 100% O2. 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 .cntdot. min-1 .cntdot. g-1, respectively. During 100% O2 administration, flow was significantly diminished in each region to 0.75 .+-. 0.04, 0.41 .+-. 0.07 and 0.06 .+-. 0.01 ml .cntdot. min-1 .cntdot. g-1, respectively. Transmural blood flow to each layer was reduced uniformly in all regions. Apparently, 100% O2 further reduces myocardial blood flow to ischemic regions.