Background: Different methods and several devices exist for measuring cardiac output by minimal invasive techniques, all based on arterial pulse contour analysis (FloTrac^®/Vigileo^®, Edwards Lifesciences; PiCCO^®, Pulsion Medical Systems; LiDCO^®/PulseCO^®, LiDCO Ltd; PRAM/Mostcare, FIAB SpA; Modelflow^®, Finapres Medical Systems). However, their measurement accuracy, especially during changing patient conditions, remains under discussion. The underlying CO measurement methods and their limitations will be presented in detail and the results of recent comparative studies between these devices and the “gold standard”, pulmonary artery catheter thermodilution (PAC TD), will be discussed.

Methods: Prospective studies and available reviews on the comparison of the pulse contour approach with the established PAC TD technique were enclosed in our meta-analysis. As far as available, the relevant results (data for the range of cardiac output, bias, percentage error) and the software versions used were included.

Results: Studies comparing the available systems for CO measurement have been performed in a variety of clinical settings. For instance, out of 53 analysed studies of CO determination by arterial pulse contour analysis, the majority shows acceptable accuracy during stable hemodynamic conditions. However, the studies under varying hemodynamic situations (vasoactive drug administration, loss of fluids etc). demonstrate insufficient accuracy (with percentage errors exceeding the 30% limit as suggested by Critchley&Critchley).

Conclusions: Under stable hemodynamic conditions CO measurements based on intermittent bolus TD and arterial pulse contour analysis seem to yield comparable Results: Further improvement and validation studies are needed to prove the reliability of CO determination in unstable patients with the systems presently available.