Original Article

An In Vitro Calibration of the Thermodilution Method of Cardiac Output Determination

The University of Chicago, Section of Pulmonary and Critical Care Medicine, Chicago, IL

^* Direct communications to: Richard Long, M.D., Critical Care Services, Room E5003, St. Boniface General HospitaL 409 Tache Avenue, Winnipeg, Manitoba, R2H 2A6, Canada

Abstract

(J. Extra-Corpor. Technol. 19[2] p. 221–227 Summer 1987, 13 refs.) The accuracy of cardiac output (Q) determinations by the indicator dilution method will depend, amongst other things, upon the precision of the instruments used to make the measurements. Using an in vitro calibration we determined the accuracy and reproducibility of the measured flow from three different thermodilution computercatheter systems in our institution. The regression equation describing the relationship between computed and true flow, Computed Flow= M (True flow) + B where M = the slope and B = the intercept of the regression line, was determined for each system. These equations defined the extent to which the system departed from 1 00% accuracy in the idealized environment of a flow-bench model. As such, they quantify the minimum error that is likely to be encountered when the same measurement is made in vivo.