In vitro studies of the pulsatile radiometric signal.

Abstract

ABSTRACTAn in vitro model system was designed to permit simultaneous measurements of blood flow, blood pressure, and the pulsatile radiometric signal during flow studies with Ringer's solution and blood of hematocrit 32,41, and 51. When the in vitro system contained a cat carotid artery, increases in blood flow were associated with increases in the pulsatile radiometric signal. Changes in the pulsatile radiometric signal were linearly related to changes in mean flow and highly correlated with changes in the pulsatile flow, mean pressure, and pulsatile pressure. Results from the regression analyses suggest that the pulsatile radiometric signal may be attributed to reflection from the artery wall. When the in vitro system contained a glass cell, increases in blood flow were associated with decreases in the pulsatile radiometric signal. There was an inverse linear relationship between the pulsatile radiometric signal and mean flow, and changes in the pulsatile radiometric signal were highly and inversely correlated with changes in pulsatile flow and pulsatile pressure. These results suggest that when recording over the cutaneous microcirculation, the pulsatile radiometric signal is in part due to changes in the red blood cell scattering and absorption coefficients.