Comparison of cardiac output values; pulse contour methods against thermodilution technique

Introduction

We evaluated the performance of the FloTrac/Vigileo system (FCO) and simultaneously obtained cardiac output (CO) values with the PiCCOplus (PCO), LiDCO™plus (LCO), Vigilance continuous pulmonary artery thermodilution (CCO) against the intermittent pulmonary artery thermodilution technique (ICO).

Methods

Data were collected during standard postoperative care in 28 cardiac surgery patients. The cardiac output data were collected at 1 hour (T1), 2 hours (T2), 4 hours (T3), 8 hours (T4), 12 hours (T5), 24 hours (T6), 36 hours (T7), and 48 hours (T8) after ICU admission. The number of observations per patient varied between four and eight. Data were analyzed with Bland-Altman statistics.

Results

Reference cardiac output (ICO) ranged from 2.90 to 8.70 l/minute, mean value of 5.12 (SD = 1.02) l/minute. Agreement between methods against the reference method are also expressed in a percentage (LOA%); that is, at low CO a small error and at high CO a higher error is observed. The distribution of errors is different among the methods (Figure 1). This is confirmed by Levine's statistics, which showed significant (F value = 20.5, P < 0.001) unequal homogeneity of the variances of the four methods. For CCO bias and limits of agreement are 0.31 and -0.99 to 1.61. Bias and limits of agreement of FCO, LCO and PCO are 0.59, -1.37 to 2.55; -0.05, -1.99 to 1.89 and -0.16, -2.60 to 2.28 l/minute, respectively.

Figure 1

Conclusions

The performance of pulse contour methods has significantly increased in the past few years, which makes comparisons with older publications invalid. The auto-calibrated FloTrac/Vigileo system can replace the initially PAC-calibrated LiDCO and PiCCO system.