The accuracy of bioimpedance cardiography in the measurement of cardiac output in comparison with thermodilution method.

BACKGROUND

Continuous noninvasive measurement of cardiac output (CO) is clinically desirable. Thoracic electrical bioimpedance (TEB) offers such a continuous noninvasive technique for the measurement of CO on a beat-by-beat basis. The purpose of this study was to compare the correlation of TEB with the thermodilution (TD) method of measuring CO during surgery.

METHODS

Eighteen patients (age 39-64 yr), with coronary artery disease undergoing coronary artery bypass graft surgery were studied. Patients were excluded if severe arrhythmias or aortic insufficiency was present before operation. Simultaneous measurements of CO were performed in each patient with the use of a 7F Swan-Ganz catheter and TEB. 128 matched pair values were obtained and compared using regression analysis. Bias (mean difference between measurements) and limits of agreement with 95% confidence limits were also calculated.

RESULTS

A good correlation (correlation coefficient, r = 0.86; TEB = 0.55 + 0.82TD, p < 0.001) between the two methods of measuring CO was observed, and the standard error was small (SE = 0.218). The mean difference between CO measurements (TEB-TD) was -0.66 L/min and had a 95% confidence interval of 0.12 to 0.98 L/min. The standard deviation of the difference was 0.915 L/min and the limits of agreement were from -2.49 to 1.17 L/min. There appeared to be a good agreement between TEB and TD CO measurement in this study.

CONCLUSIONS

Technological advances in TEB have resulted in more accurate CO measurements. Such device offers a noninvasive alternative to the TD technique for the determination of CO, and may potentially be very useful as a powerful, noninvasive, continuous technique for monitoring cardiac function in the clinical setting.