Parameter sensitivity analysis: application to model predictions of transport parameters governing arterial wall uptake of /sup 14/C-4 cholesterol

The authors have applied nonlinear (Marquardt) regression techniques to concentration profiles of /sup 14/C-4 cholesterol within the arterial wall of excised canine carotids perfused for two hours under various hemodynamic conditions. The resulting estimates of the transport parameters of Peclet number (Pe), effective diffusivity (D), endothelial vesicular Biot number (Be), and endothelial phenomenological rejection coefficient (Re) serve as input to a sensitivity analysis of the inter-dependence of model parameters. Here the best-fit value of each parameter estimate is perturbed by 10% and the resulting change in the predicted concentration profile used to calculate individual parameter sensitivities according to algorithms defined in the text authored by P.M. Frank. Their results indicate that the parameters Be and Re are indistinguishable at all locations within the wall substance (x/L) except the endothelial cell border (x/L=0). A similar finding is true for the parameter pair Pe-D when x/L > 0.4, i.e. beyond the medial-adventitial junction. The implications are that the present mathematical model be modified to exclude an assessment of Be, especially when the anatomic integrity of the endothelial layer is compromised, and that perfusion times be extended to allow advancement of convective and diffusive fronts into the adventitia.