Evaluation of a thoracic bioimpedance cardiac output monitor during cardiac catheterization

Objective: To evaluate the accuracy and precision of an advanced thoracic b ioimpedance cardiac output monitor by comparing it with conventional thermo dilution. Design: Prospective data collected from 47 patients undergoing routine card iac catheterization. The new bioimpedance system differs from its predecess ors in electrode system configuration, advanced signal processing, use of a modified Kubicek equation, and a reliable estimate of left ventricular eje ction time from the time derivative bioimpedance signals. Setting: A cardiac catheterization laboratory in a university affiliated te aching hospital. Patients: A series of 47 relatively homogenous patients undergoing routine cardiac catheterization for suspected cardiac disease. Measurements and Main Results: The data from the first 20 patients was used to determine optimal values for coefficients in the bioimpedance cardiac o utput equations. The coefficients found were used when the system was teste d in the subsequent 27 patients. For the last 27 patients, a total of 80 si multaneous pairs of cardiac output measurements were made by conventional t hermodilution end by thoracic bioimpedance. The mean difference between the two methods was -0.31 L/min and the standard deviation of the differences was (0.76 L/min), The correlation coefficient was r(2) = .72 (p < .001). Conclusions: The correlation between conventional thermodilution and thorac ic bioimpedance cardiac output estimates was good and the standard deviatio n of the differences was lower than that reported for commercially availabl e devices. The system can be used in the cardiac catheterization lab for re liable and continuous noninvasive measurement of cardiac output.