Background and Goal
The ccNexfin is a device that can determine cardiac output non-invasively from blood pressure waveform analysis. It remains matter of debate whether this uncalibrated, non-invasive, cardiac output measurement with ccNexfin (NEXCO) can substitute gold-standard, invasive, pulmonary artery catheter derived cold-bolus thermodilution cardiac output (PACCO). We tested agreement between NEXCO and PACCO in a multi-centre study in the largest sample size of patients to date. 

Materials and Methods: 
We included fifty-five patients undergoing cardiac surgery in three academic hospitals and measured PACCO and NEXCO simultaneously after induction of anaesthesia, before the onset of cardiopulmonary bypass. Main outcome measures were Pearson correlation and Bland-Altman analysis of bias and precision. Percentage error was calculated as the error of NEXCO divided by absolute PACCO. All data is mean (S.D.) or n (%).

Results and Discussion:
Fifty-one measurement pairs were available for analysis. Mean NEXCO was 4.04 (1.24) and mean PACCO was 3.96 (0.99) l·min-1, bias was 0.09 (0.76) l·min-1. Pearson’s correlation coefficient was 0.79 and mean percentage error was 37%. Forty-six (90%) of all measurements had a percentage error <30%. Performance of NEXCO seems to be similar to reported performance of semi-invasive techniques including pulse contour analysis, oesophageal Doppler and transthoracic bioimpedance.

Conclusion: NEXCO and PACCO agree with a low systematic bias. However, mean percentage error was above the pre-defined 30%. We conclude that NEXCO cannot replace invasive CO measurement, but NEXCO may be interchangeable with  a semi-invasive technique.

Accuracy of ccNexfin CO-trek cardiac output versus cold-bolus thermodilution cardiac output