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Chapter 16: Cardiac Output Monitoring
User Manual
16.1 GENERAL
Cardiac Output (C.O.) is the volume of blood pumped by the heart ventricle per minute. The
measurement unit is litres per minute (L/min).
To understand the clinical importance of measuring cardiac output, consider that the primary
function of the heart is to deliver sufficient oxygenated blood to meet the metabolic needs of the
body tissues. The cardiac output measurement invasively measures cardiac output and other
hemodynamic parameters using a technique called thermodilution. C.O. measurements in
SAADAT monitors are carried out using the right heart thermodilution method. This method is
known as "gold standard" of C.O. measurement.
C.O. Measurement using the Right Heart Thermodilution Method
In the right heart thermodilution method, a cold fluid of known volume and temperature is
injected into the right atrium thought a pulmonary artery catheter (PAC). The injected fluid
mixes with the blood in the right ventricle and the change in blood temperature is measured with
a thermostat situated in the distal end of the catheter in the pulmonary artery.
After injection, the blood temperature descends and then rises smoothly to reach its initial state.
The lower cardiac output value, the colder temperature of injectate solution. Cardiac output is
inversely proportional to the area under the thermodilution curve (Refer to figure 15-1).
16-2
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