Saline and thermal dilution flow measurements: evaluation by means of an open hydraulic model

A simple open hydraulic model was constructed with the main objective of making comparative evaluations of flow rate measurements, with saline and thermal dilution. In the range of 0.5 to 3.5 l/min, it was found that saline indicator gave a slight underestimation (in the order of 2%) while the thermal indicator showed a minor overestimation of approximately 1%. These values wee taken from the regression equations F (saline) = 0.945 F (real) + 0.0351 and F (thermo) = 1.020 F (real) - 0.0144, both in l/min. Correlations were higher than 0.99 in the two cases. Considering the overall error range, the thermodilution produced a value approximately twice that of saline (-21 to 25% versus -12 to +11%). However, this is not necessarily extendable to living organisms. The model was found useful for test and calibration of detecting cells and for teaching purposes.