Cardiac output and stroke volume variation measured by the pulse wave transit time method: a comparison with an arterial pressure-based cardiac output system

Hemodynamic monitoring is mandatory for perioperative management of cardiac surgery. Recently, the estimated continuous cardiac output (esCCO) system, which can monitor cardiac output (CO) non-invasively based on pulse wave transit time, has been developed. Patients who underwent cardiovascular surgeries with hemodynamics monitoring using arterial pressure-based CO (APCO) were eligible for this study. Hemodynamic monitoring using esCCO and APCO was initiated immediately after intensive care unit admission. CO values measured using esCCO and APCO were collected every 6 h, and stroke volume variation (SVV) data were obtained every hour while patients were mechanically ventilated. Correlation and Bland–Altman analyses were used to compare APCO and esCCO. Welch’s analysis of variance, and four-quadrant plot and polar plot analyses were performed to evaluate the effect of time course, and the trending ability. A p-value < 0.05 was considered statistically significant. Twenty-one patients were included in this study, and 143 and 146 datasets for CO and SVV measurement were analyzed. Regarding CO, the correlation analysis showed that APCO and esCCO were significantly correlated (r = 0.62), and the bias ± precision and percentage error were 0.14 ± 1.94 (L/min) and 69%, respectively. The correlation coefficient, bias ± precision, and percentage error for SVV evaluation were 0.4, − 3.79 ± 5.08, and 99%, respectively. The time course had no effects on the biases between CO and SVV. Concordance rates were 80.3 and 75.7% respectively. While CO measurement with esCCO can be a reliable monitor after cardiovascular surgeries, SVV measurement with esCCO may require further improvement.