Cardiac output measurement

Measurement of cardiac output provides an estimate of whole body perfusion, oxygen delivery and ventricular function. This article aims to provide an overview of cardiac output measurement techniques, with an emphasis on their principles of operation and limitations. Cardiac output can be measured in terms of volume displacement or velocity of blood flow. Although thermodilution with a pulmonary artery catheter has been used extensively, less invasive technologies such as Doppler echocardiography, pulse contour analysis, impedance plethysmography and Fick partial rebreathing are increasingly used. The advantages and limitations of each technique are different and each technique may find a specific niche in the armamentarium of the clinician.