Time Domain Method to Identify Simultaneously Parameters of the Windkessel Model Applied to the Pulmonary Circulation

Lumped models are frequently used to provide a satisfactory description of the hemodynamic properties of the pulmonary vasculature. The purpose of this study is to describe a method to identify simultaneously the parameters values of windkessel models components. The following equation was used to obtain R1 (characteristic resistance), R2 (peripheral resistance), C (total compliance) and L (inertance): [formula: see text] where ki are the following functions of L, R1, R2 and C: [formula: see text] To assess the accuracy of the method, estimates of R1, R2, and C were compared to characteristic impedance Rc, vascular resistance PVR and pulmonary arterial compliance Cd respectively computed from referenced methods. Comparison between R1 and Rc, PVR and R1 + R2, C and Cd were obtained in 5 anaesthetised pigs during basal conditions and after endotoxin-shock. The results indicate that in both conditions, comparisons evidenced highly significant correlations between values computed by the different approaches (p < 0.0001). Although our method yielded to consistently lower values than values provided by referenced methods, the results were concordant with respect to the expected response of pulmonary vasculature to endotoxin insult. We conclude that our method of identification is suitable for the assessment of lumped parameters windkessel model estimates. The main interest is that actual resistance and compliance values can be obtained easily and simultaneously by a global method approach.