Changes in Arterial Dilution Curves Associated With Blockage of Abdominal Aorta, Hypoxia and Hemorrhage

¹ From the Department of Physiology, University of Miami School of Medicine, Coral Gables, Florida

The dye T-1824 and red cells marked with P³² were injected into the pulmonary artery of dogs. The characteristics of arterial dilution curves after blocking the descending aorta, after hypoxia and after transfusion following hemorrhage were studied. After pulmonary pressure was raised by blocking the aorta, the figure for peak concentration time divided by appearance time (PTC/AT) was increased, the concentration of labels rose to three-fourths of peak concentration more quickly and the figure for peak concentration divided by mean concentration (PC/MC) diminished. The results following hypoxia were variable. In only one out of eight dogs studied were the changes similar to those described above. In five opposite changes were found and in two the changes were mixed. Transfusion following hemorrhage resulted in changes which showed no regular pattern. The changes with blocking of aorta are those which we would predict if pulmonary shunts open. Those with hypoxia indicate that the opposite changes have occurred.