Purpose: The aim of this study was to evaluate the reliability of a new continuous cardiac output (CCO) monitoring device (Qvue/OptiQ system; Abbott Critical Care Systems, Mountain View, CA) based on the pulsed warm thermodilution technique in critically ill medical patients.
Methods: Nineteen patients with cardiogenic or septic shock were included in the study. Pairs of CCO and intermittent bolus cardiac output (ICO) were noted at least every 6 hours for determination of bias, precision, and limits of agreement. Simultaneously, blood samples were collected, and arterial-venous oxygen content difference (C[a-v]O2) was determined. A multiple stepwise logistic regression was used to identify situations associated with a CCO-ICO difference exceeded 20%. A multiple linear regression was performed to analyze the respective accuracy of CCO and ICO to predict the variations of C[a-v]O2.
Results: A total of 203 pairs of cardiac output measurements was obtained. The bias was 0.12 L/min (1.2% of pairs mean) and the precision 1.0 L/min (13%). The 95% limits of agreement were between -1.7 L/min (-25%) and 1.9 L/min (+26%). Low blood temperatures and heart rates above 120 beats/min were significantly associated with a ICO-CCO difference higher than 20%. In a multiple linear regression, CCO was significantly correlated with C[a-v]O2, an independent reflection of the patient's cardiac output; by contrast, ICO did not.
Conclusion: These results suggest that ICO and CCO measurement by the Qvue/OptiQ system are interchangeable, except for temperature or heart rate extreme values.