Purpose Estimated continuous cardiac output (esCCO) is a new and noninvasive cardiac output (CO) monitoring device using pulse wave transit time. The aim of this study was to assess rapid changes in CO using esCCO (DCO esCCO ) without invasive calibration and to compare the results with those using transthoracic Doppler echocardiography (DCO TTE ). Methods Fifty-four consecutive patients were enrolled in this study following elective cardiac surgery. The CO esCCO and CO TTE were collected during four consecutive steps: 1) at baseline, 2) during passive leg raising (PLR), 3) at return to baseline, and 4) after a fluid challenge. The relationship between DCO esCCO and DCO TTE induced by PLR and a fluid challenge was assessed and a polar plot analysis was performed. Relationship, Bland-Altman analysis, and percentage error for absolute values of CO esCCO and CO TTE were also performed. Results Twenty-four patients were excluded from the analysis. No correlation was found between DCO esCCO and DCO TTE during PLR (r = 0.07; P = 0.732; n = 30) and after a fluid challenge (r = 0.24; P = 0.394; n = 14). The polar plot analysis showed that 21 data points (87%) of significant changes in CO were above the 30°radial sector lines and confirmed that esCCO was unable to track changes in CO. A weak positive relationship was found between absolute values of CO esCCO and CO TTE (r = 0.28; P = 0.004). Bias, precision, and limits of agreement were 0.25 LÁmin -1 , 2.4 LÁmin -1 , and -4.4 to 4.9 LÁmin -1 , respectively. The percentage error was 80%. Conclusions Estimated continuous cardiac output without external calibration seems unable to assess rapid changes in CO following cardiac surgery and was not interchangeable with transthoracic Doppler echocardiography.

No abstract