Cardiac Output Computer Simulator
created by Barry Voss
Overview of the Thermodilution Cardiac Output Computer Simulator
In clinical practice cardiac output can be estimated with the thermodilution method. A catheter is inserted into the pulmonary artery. The catheter has a thermistor in the tip measuring the temperature of the blood. A second thermistor is inserted into a bag of saline to measure its temperature (the saline is the injectate). The injectate is typically room temperature or iced saline (0 degrees centigrade). On the cardiac output computer the user enters a 'constant'. This is a number determined by the manufacturer that tells the computer the temperature of the injectate, and the volume of the injectate over a prescribed period of time. The constant is a number that the user looks up on a chart provided by the manufacturer. A typical injectate volume would be 10 ml, and a typical time would be 3 seconds. The user presses a 'start measurement' button on the computer and delivers the injectate via syringe into the catheter and thus into the artery of the patient. The thermistor at the tip of the catheter measures the temperature differential of the blood/saline over time and performs a calculation estimating the cardiac output. Cardiac output typically run in the 3 to 8 liters per minute range. This process is very technique dependant so three measurements are done to get a good average.
Cardiac output is measured by placing a catheter with a thermistor on the tip through the right ventricle into the pulmonary artery, injecting cold saline into the catheter, and integrating the resulting pulmonary artery temperature profile...
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