Correction for apparent prolongation of mean transit time resulting from response time in a thermodilution system

A method of correcting an apparent prolongation in the measured transit time (MTT) resulting from the response time of the thermodilution system was investigated. The mean response times (MRTs) were measured for five commercially available thermistor-tipped catheters by recording their step function response curves. Using a flow loop model filled with saline through a mixing chamber, pairs of thermodilution curves were recorded simultaneously with pairs of catheters, and the influence of MRT on MTT was studied for the constant flow rates of 1-6 L/min. The difference in MRTs between a pair of thermodilution systems correlated with the difference in MTTs between a corresponding pair of thermodilution curves, yielding an equation. It was concluded that the apparent prolongation of MTT due to response time can be eliminated by subtracting the MRT from the measured MTT.<
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