NONINVASIVE EVALUATION OF ABDOMINAL AORTIC PROPERTIES - LUMPED CIRCUIT MODEL AND ESTIMATION OF ITS PARAMETERS

To non-invasively determine abdominal aortic properties, a five-elemen t lumped circuit model was adopted. The model consists of resistance d ue to blood viscosity (RI), inertia of blood flow, compliances of the vessel (C1, C2), resistance of the peripheral arteries (R2) and the im pedance of the femoral arteries (termination). Patterns of the central velocity of the upper abdominal aorta and the femoral artery are meas ured by pulsed Doppler echocardiography, and contours of flow volume r ates are calculated. The pressure pattern of the lower limb is recorde d by a pulse wave transducer and corrected according to sphygmomanomet er values. Contours are transformed into respective Fourier transform components. The current transfer function is described theoretically a nd calculated from the acquired Fourier components. Values of every el ement are evaluated by the nonlinear least squares method. In 94 subje cts (17-92 years), the values of each element are estimated. R2 values are greater in the elderly group than in the young group and r(1) (R1 /cm) increased with age. This model demonstrates that vessel complianc e (c(1)+c(2) (C1+C2/cm)) decreases with age, and it is suggested that this may be a useful marker of arteriosclerosis.