Sensitivity analysis and parameter identification for a model of left ventricular mechanics and the systemic arterial load
Paulsen, Robert Alan
Clark, John W.
Master of Arts
An identification scheme for the determination of several parameters associated with a third-order lumped-parameter model of the systemic arterial system has been developed previously (1). In the present study, a parameter sensitivity analysis of this model is conducted in conjunction with the identification scheme. This analysis indicates that the state variables of this system are not unduly sensitive to changes in the model parameters or initial conditions. It also indicates the relative sensitivities of the individual model parameters and provides valuable insight into the behavior of the arterial model. This insight resulted in a significant simplification of the identification scheme (1) that makes it more likely to be employed in practice. The arterial model mentioned above is driven by aortic root flow f (t), and this waveform is approximated by either of two methods, one involving the measurement of left ventricular pressure, the other a measurement of left ventricular volume. Adequate specification of the model driving waveform f (t) is very important to the identification process and, therefore, the abilities of the aforementioned methods in approximating fa(t) under practiced measurement conditions are investigated. The left ventricular mechanics for an individual patient are specified by the elastance curve in this study. Two clinical approaches, the direct and the indirect, to the estimation of left ventricular elastance are presented. A multiple measurement technique is used to solve for end-diastolic volume in the direct problem and an approximate method for the determination of the aortic valve resistance is suggested for the solution of the indirect problem. A sensitivity analysis of the left ventricular model proved useful in the analysis of both approaches.