Continuous Estimation of Cardiac Output in Critical Care: A Noninvasive Method Based on Pulse Wave Transit Time Compared with Transpulmonary Thermodilution

Figure 1

Comparison between CO_TPTD and CO_esCCO. (a) Correlation between CO_TPTD and CO_esCCO estimates at baseline. Each dot represents one patient. Correlation between the two estimates was significant (r = 0.742, ). The regression coefficient was 0.52, and the intercept was 2.21 l/min (CO_esCCO = 0.52 × CO_TPTD + 2.21 l/min) indicating that at low CO, the esCCO was overestimated and at high cardiac output, underestimated CO as compared to the TPTD method. (b) The Bland–Altman plot of CO_TPTD and CO_esCCO, Each dot represents a pair of simultaneous cardiac output measurements by esCCO and TPTD of the same patient. The midhorizontal line marks the average difference between CO_TPTD and CO_esCCO (bias; 1.61 l/min). The upper and lower horizontal lines represent the 95% confidence interval of the difference between CO_TPTD and CO_esCCO (limits of agreement; −1.76 and +4.98 l/min). (c) The four quadrant plot of the correlation between CO_esCCO and CO_TPTD. Each dot represents the change of cardiac output over an 8-hour period (M_8 h − M_{mean baseline}) assessed by transpulmonary thermodilution (TPTD) and continuous cardiac output (esCCO). The regression fitted (ΔCO_esCCO = 0.35 × CO_TPTD − 0.09 l/min) supported that a change in cardiac output overtime was underestimated by the esCCO as compared to the TPTD method.

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