Performance of three minimally invasive cardiac output monitoring systems.

We evaluated cardiac output (CO) using three new methods – the auto-calibrated FloTrac–Vigileo (COed), the non-calibrated Modelflow (COmf ) pulse contour method and the ultra-sound HemoSonic system (COhs) – with thermodilution (COtd) as the reference. In 13 postoperative cardiac surgical patients, 104 paired CO values were assessed before, during and after four interventions: (i) an increase of tidal volume by 50%; (ii) a 10 cm H2O increase in positive end-expiratory pressure; (iii) passive leg raising and (iv) head up position. With the pooled data the difference (bias (2SD)) between COed and COtd, COmf and COtd and COhs and COtd was 0.33 (0.90), 0.30 (0.69) and −0.41 (1.11) l.min−1, respectively. Thus, Modelflow had the lowest mean squared error, suggesting that it had the best performance. COed significantly overestimates changes in cardiac output while COmf and COhs values are not significantly different from those of COtd. Directional changes in cardiac output by thermodilution were detected with a high score by all three methods. [ABSTRACT FROM AUTHOR]