Evaluation of a new arterial pressure-based cardiac output device requiring no external calibration

Abstract

Several techniques have been discussed as alternatives to the intermittent bolus thermodilution cardiac output (CO_PAC) measurement by the pulmonary artery catheter (PAC). However, these techniques usually require a central venous line, an additional catheter, or a special calibration procedure. A new arterial pressure-based cardiac output (CO_AP) device (FloTrac™, Vigileo™; Edwards Lifesciences, Irvine, CA, USA) only requires access to the radial or femoral artery using a standard arterial catheter and does not need an external calibration. We validated this technique in critically ill patients in the intensive care unit (ICU) using CO_PAC as the method of reference. We studied 20 critically ill patients, aged 16 to 74 years (mean, 55.5 ± 18.8 years), who required both arterial and pulmonary artery pressure monitoring. CO_PAC measurements were performed at least every 4 hours and calculated as the average of 3 measurements, while CO_AP values were taken immediately at the end of bolus determinations. Accuracy of measurements was assessed by calculating the bias and limits of agreement using the method described by Bland and Altman. A total of 164 coupled measurements were obtained. Absolute values of CO_PAC ranged from 2.80 to 10.80 l/min (mean 5.93 ± 1.55 l/min). The bias and limits of agreement between CO_PAC and CO_AP for unequal numbers of replicates was 0.02 ± 2.92 l/min. The percentage error between CO_PAC and CO_AP was 49.3%. The bias between percentage changes in CO_PAC (ΔCO_PAC) and percentage changes in CO_AP (ΔCO_AP) for consecutive measurements was -0.70% ± 32.28%. CO_PAC and CO_AP showed a Pearson correlation coefficient of 0.58 (p < 0.01), while the correlation coefficient between ΔCO_PAC and ΔCO_AP was 0.46 (p < 0.01). Although the CO_AP algorithm shows a minimal bias with CO_PAC over a wide range of values in an inhomogeneous group of critically ill patients, the scattering of the data remains relative wide. Therefore, the used algorithm (V 1.03) failed to demonstrate an acceptable accuracy in comparison to the clinical standard of cardiac output determination.