Haemodynamic assessment of critically ill patients is an essential diagnostic step for verification of sufficient organ perfusion and oxygen delivery and, moreover, one of the most important tasks of critical care medicine. During the last decades, cardiac output measurement has become a cornerstone topic with simultaneous development of various methods for its continuous or intermittent monitoring.
Echocardiography has been recognized as a non-invasive, nevertheless accurate method for the cardiac output measurement. It is especially important to understand the basic principles of ultrasound in order to use echocardiography properly, and to realize not only its advantages but also its limits to avoid possible errors or misinterpretations of the measurements.