Objective: To evaluate the performance of arterial pressure-based cardiac output (APCO) and pulse wave transit time-based cardiac output (esCCO) monitors in Thai patients undergoing cardiac surgery with cardiopulmonary bypass.
Material and Method: The authors studied fifty Thai surgical patients undergoing coronary artery bypass graft surgery (CABG) with cardiopulmonary bypass and requiring pulmonary artery catheters and radial artery catheter placement as a standard of clinical care. All patients were measured for APCO using the Vigileo/FloTracTM and esCCO using the esCCOTM monitoring system. The data were compared to thermodilution cardiac output (TDCO) monitoring as a reference method, simultaneously at pre-induction of anesthesia, post-induction, and every 30 minutes thereafter until the completion of the surgery. The bias and precision were assessed using Bland-Altman analysis.
Results: 310 pairs of simultaneous measurements of APCO vs. TDCO and 303 pairs of esCCO vs. TDCO were obtained from fifty patients. Both APCO (R = 0.53, p<0.0001) and esCCO values (R = 0.56, p<0.0001) were correlated with TDCO values. Either of the changes in APCO (R = 0.63, p<0.0001) or any changes in esCCO (R = 0.60, p<0.0001) were correlated with changes in TDCO. For APCO relative to TDCO, the bias, precision, and the limits of agreement were 0.70, +1.63, and -2.5 to 3.9 L/min while of esCCO were 1.20, +1.59, and -1.9 to 4.3 L/min, respectively. Comparisons of the bias of APCO and esCCO revealed a level of significance of p<0.001.
Conclusion: Despite the overestimation of CO measurements, APCO and esCCO calibrated with patient information has shown an acceptable trend as compared to TDCO in Thai patients undergoing CABG with cardiopulmonary bypass. Compared to esCCO, APCO demonstrated no significant differences of precision however; a lower mean bias was exhibited.

Keywords: Pulse wave transit time, Pulse contour, Cardiac output