Cardiac output

Cardiac output (CO, also denoted by the symbols and ), is a term used in cardiac physiology that describes the volume of blood being pumped by the heart, in particular by a left or right ventricle, per unit time. CO values can be represented using many physical units, such as dm³/min and L/min..

Because cardiac output is related to the quantity of blood delivered to various parts of the body, it is an important indicator of how efficiently the heart can meet the demands of the body. For instance, infections are correlated with high CO and heart failure with low CO.

Along with stroke volume (SV), cardiac output is a global blood flow parameter of interest in hæmodynamics – the study of the flow of blood under external forces. The factors affecting stroke volume and heart rate also affect cardiac output. The figure to the right illustrates this dependency and lists some of these factors. A detailed hierarchical illustration is provided in a subsequent figure.

There are many methods of measuring CO, both invasively and non-invasively, each with its own advantages and drawbacks. No standard or reference measurement against which all of these methods can be compared exists.