Background
The measurement of cardiac output in critically ill patients is complicated by rapid pathophysiological changes. The aim of this study was to compare the recently developed Arterial Pressure Cardiac Output algorithm (APCO) with transpulmonary thermodilution (TDCO). Clinical and hemodynamic parameters were tested for their impact on the measurements.
Material and Method
Twenty septic patients were examined. Cardiac output measurements were performed simultaneously on 3 consecutive days. The data were evaluated using regression analysis and the Bland Altman approach.
Results
Bland Altman analysis presented a bias of 0.72 L/min and limits of agreement of 2.16 to 3.61 L/min for TDCO vs. APCO. Statistically significant covariables in the regression analysis were systemic vascular resistance (p<0.001), mean arterial pressure (p<0.001), cardiac function index (p=0.01), global end-diastolic index (p=0.02) and stroke volume index (p=0.005). Multiple linear regression analysis showed the residual percentage error decreased from 49.1% to 21.5%.
Conclusions
The APCO algorithm provides a broad range of hemodynamic measurements with a minimally invasive approach and simple access to the patient's hemodynamic state. However, an underestimation at high cardiac output and an overestimation at low cardiac output relative to transpulmonary thermodilution were observed in septic patients. Therefore, the APCO algorithm in its current state cannot be substituted for transpulmonary thermodilution.

Keywords: Monitoring, Physiologic - methods, Lung - physiopathology, Linear Models, Cardiac Output - physiology, Blood Pressure - physiology, Aged, 80 and over, Sepsis - physiopathology, Thermodilution - methods