Transit time flow measurement: Experimental validation and comparison of three different systems

Background. Bloodflow measurements are of major clinical importance for qua lity control in vascular surgery. They allow detection of low-flow situatio ns which may influence outcome adversely. The purpose of the present study was to validate three different flow systems for measuring absolute blood f low. Methods. Measurements were performed in an experimental flow model using ar teries and veins and blood or saline at two different temperatures. As a re ference method true flow was measured by volume sampling. Results. Correlation coefficients between transit time flow and true flow m easurements ranged between 0.71 and 0.92. Systematic overestimation and und erestimation of transit time flow were observed, but after second-order cor rection all correlations were excellent, ranging from 0.93 to 0.95 irrespec tive of flow medium and temperature. Conclusions. Transit time flow measurements are exact and reproducible. Sec ond-order correction yields good accuracy and high precision, with minimal differences among the three systems evaluated. (Ann Thorac Surg 2000;70:212 -7) (C) 2000 by The Society of Thoracic Surgeons.