Redistribution of visceral blood volume in upright exercise in healthy volunteers.

Exercise induced changes in the blood volume of visceral organs (cardiopulmonary and liver, spleen, and kidneys) were determined by scintillation camera imaging of the distribution of technetium-99m-labeled red blood cells in the thorax and abdomen of ten healthy adult volunteers. Graded upright bicycle exercise was performed to the point of exhaustion with the volunteer positioned with his/her back to the scintillation camera and data recording was synchronized to the pedal cycle to minimize patient motion artifacts within the data. The first image from each level of exercise was analyzed by placing regions of interest over the spleen, liver, kidneys, and right lung. The counts in each organ were expressed as a percent of activity at zero workload. Analysis of data using Hotelling's t-squared analysis to see if overall differences existed between the last four measurements (up to the time of exhaustion) regarding percent change from baseline for spleen, kidney, liver, and right lung were made. The splanchnic bed had a significant decrease in blood volume. The spleen decreased 39%, while the liver decreased 14%. For the kidney and liver, no significant differences were achieved (p greater than 0.24, p less than 0.15, respectively). The lung increased its blood volume to 128% of control, significant with p less than 0.02. This data demonstrates that in healthy volunteers there is normal redistribution of blood volume during maximal exercise with a significant reduction in blood volume of the spleen as well as a significant rise in blood volume within the lungs.