Estimating the driver function of a cardiovascular system model

The time varying elastance of the left and right ventricles, also called the driver functions, are the inputs to a previously developed cardiovascular model. However these functions cannot normally be measured directly in an Intensive Care Unit (ICU), as they require both ventricle volume and pressure waveforms. This paper develops a method to construct both driver functions from measurements which are more commonly available in an ICU. Specifically the aortic pressure and pulmonary artery pressure waveforms. The information used from the pulmonary artery pressure can be found from the central venous pressure and ECG, however these were not available for this study. This paper also details a method to locate specific points of interest in the aortic and pulmonary artery pressures, such as the dicrotic notch. The driver functions that were constructed with a median error of 1.32% and 2.54% for the left and right respectively, with a 90th percentile of 3.67% and 9.43% respectively, and tracked all the physiologically meaningful points on the driver function, such as the start and end of ejection and the maximum ascending gradient.