Levenberg-Marquardt estimation for accurate and efficient continuous measurement of cardiac output

Thermodilution is a standard method for measurement of cardiac output. Thermodilution requires the injection of a thermal indicator (or heat pulse) into the right side of the heart and measurement of the resulting temperature fluctuation in the pulmonary artery. Cardiac output is then estimated from the temperature fluctuation. For continuous thermodilution, relatively small amounts of thermal energy are injected, producing a thermal pulse with a poor signal-to-noise ratio. Estimation of cardiac output can be improved by fitting the thermal data to a pulse model and calculating the cardiac output from the resulting model. The authors have developed an efficient implementation of the Levenberg-Marquardt (LM) nonlinear fitting method to fit thermodilution data to a thermodilution pulse model, and they have compared the performance of their LM fit implementation to simpler methods