P2.25 ECHOCARDIOGRAPHIC VALIDATION OF A NOVEL METHOD FOR NONINVASIVE ESTIMATION OF CARDIAC OUTPUT BASED ON PULSE CONTOUR ANALYSIS

Abstract

Surgical or critically ill patients often require continuous assessment of cardiac output (CO) for diagnostic purposes or guiding therapeutic interventions. A new method of non-invasive estimation of CO, based on pressure wave analysis, has been recently developed, but its validity has been examined only in silico. Aim of this study was to evaluate the reproducibility, precision and accuracy of the “Systolic Volume Balance” method (SVB). Methods: Twelve subjects underwent 2-D transthoracic echocardiography (Doppler) for CO measurement which was used as reference value. The application of SVB method required aortic pressure wave analysis and estimation of total arterial compliance (Ct). Aortic pulses were derived by mathematical transformation of radial pressure waves recorded by applanation tonometry (SphygmoCor). Ct was estimated by the “pulse pressure” method. The agreement, association, variability, bias and precision between the reference (Doppler) and estimated (SVB) values of CO were evaluated by Spearman correlation coefficient, intraclass correlation coefficient (ICC), coefficient of variation (CV), root mean square error (RPSE), mean difference, SD of differences (SDD), percentage error (PR) and Bland-Altman analysis. Results: Both SVB and Doppler provided highly reproducible measures of CO when two repeated measurements were performed (ICC>0.9, SD of difference <0.4 L/min, CV<5%, PR<17%). CO estimation by the SVB method was comparable with the respective measure by Doppler indicating a good agreement and accuracy (Table). Parameter Value Mean difference (L/min) 0.780 Standard deviation of difference (L/min) 0.323 Limits of agreement (L/min) 0.15–1.41 Coefficient of variation (%) 13.0 Root mean squared error (L/min) 0.678 Spearman correlation coefficient 0.939 Intraclass correlation coefficient 0.797 Percentage error (%) 20 Table.Accuracy and precision of CO estimation by the SVB method compared to the reference method (Doppler). Conclusion: CO estimation by the SVB method is highly reproducible and accurate in comparison with the CO measurement by Doppler. Future studies, though, are required to assess the clinical utility of this method.