A two-stage identification scheme for the determination of the parameters of a lumped parameter model of the left heart and systemic circulation
Ling, Robert Y. B.
Clark, John W.
Master of Science
In this study, a clinically-oriented, lumped parameter model of the human systemic circulatory system and the left ventricle is presented and identification of the model parameters is achieved by using a two-stage parameter estimation scheme that utilizes averaged pressure data (obtained from a single solid-state transducer) at three anatomical sites (proximal brachial artery, ascending aorta and left ventricle). The model parameters obtained using the estimation scheme are reasonable in a physical sense and provide a good fit to aortic and brachial pressures. The flow waveform at the aortic root can be computed during the systolic portion of the cycle, and from this waveform, instantaneous left ventricular volume (LW) changes can be predicted. As a check on the method, instantaneous LW is measured on the same patient via single plane cineangiography and compared with model generaged curves that employ the measured cineangiographic value of end-diastolic volume. In addition, the modulus and phase angle of the ascending aorta impedance, computed from the parameter values of the model, compare favorably with those obtained from more complex simulations as well as with clinical measurements. The method is simple, utilizes only pressure data (which is usually recorded with very little measurement error), and uses measurement techniques that are currently routinely employed in cardiac catheterization laboratories. The identification scheme provides an estimate of lumped proximal and distal arterial load parameters, aortic valve resistance, ascending aortic flow, ventricular volume changes, stroke volume and ejection fraction, for an individual patient.