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

Background: Bloodflow measurements are of major clinical importance for quality control in vascular surgery. They allow detection of low-flow situations which may influence outcome adversely. The purpose of the present study was to validate three different flow systems for measuring absolute blood flow.

Methods: Measurements were performed in an experimental flow model using arteries and veins and blood or saline at two different temperatures. As a reference method true flow was measured by volume sampling.

Results: Correlation coefficients between transit time flow and true flow measurements ranged between 0.71 and 0.92. Systematic overestimation and underestimation of transit time flow were observed, but after second-order correction all correlations were excellent, ranging from 0.93 to 0.95 irrespective of flow medium and temperature.

Conclusions: Transit time flow measurements are exact and reproducible. Second-order correction yields good accuracy and high precision, with minimal differences among the three systems evaluated.