Radioactive microsphere partitioning of blood flow between capillaries and arteriovenous anastomoses in skin of conscious sheep.

Using radioactive plastic microspheres in conscious sheep, cardiac output is measured by dose injection into a vein, and sampling from the pulmonary artery. Partition of organ blood flow between capillaries and arteriovenous anastomoses is derived from cardiac output and the radioactivity in pulmonary artery blood sampled after dose injection into the artery supplying the organ. Validation tests are presented. The hindlimb is shown to be a suitable model for studying thermal influences on skin blood flow. In contrast to other techniques or previous applications of microspheres: (a) conscious, chronically prepared animals are used, (b) there is no need to kill the animal to obtain results, (c) only small doses are necessary, (d) the one nuclide label can be used repeatedly, and (e) there is no need for precisely matched doses.