Performances of three minimally invasive cardiac output monitoring systems

We evaluated cardiac output (CO) using three new methods – the auto-calibrated FloTrac–Vigileo (CO_ed), the non-calibrated Modelflow (CO_mf ) pulse contour method and the ultra-sound HemoSonic system (CO_hs) – with thermodilution (CO_td) 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 CO_ed and CO_td, CO_mf and CO_td and CO_hs and CO_td 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. CO_ed significantly overestimates changes in cardiac output while CO_mf and CO_hs values are not significantly different from those of CO_td. Directional changes in cardiac output by thermodilution were detected with a high score by all three methods.<br />