In vivo parameter identification in arteries considering multiple levels of smooth muscle activity

Abstract

In this paper an existing in vivo parameter identification method for arteries is extended to account for smooth muscle activity. Within this method a continuum-mechanical model, whose parameters relate to the mechanical properties of the artery, is fit to clinical data by solving a minimization problem. Including smooth muscle activity in the model increases the number of parameters. This may lead to overparameterization, implying that several parameter combinations solve the minimization problem equally well and it is therefore not possible to determine which set of parameters represents the mechanical properties of the artery best. To prevent overparameterization the model is fit to clinical data measured at different levels of smooth muscle activity. Three conditions are considered for the human abdominal aorta: basal during rest; constricted, induced by lower-body negative pressure; and dilated, induced by physical exercise. By fitting the model to these three arterial conditions simultaneously a unique set of model parameters is identified and the model prediction agrees well with the clinical data.

Keywords: Artery; In vivo; Parameter identification; Smooth muscle activity.

Fig. 1

Schematic drawing of the experimental setup for simultaneous measurement of blood pressure and inner radius in the abdominal aorta during rest, lower-body negative pressure, and physical exercise

Fig. 2

Measured pressure-radius loops and model predictions for subject I. The solid red lines are the model predictions of the three arterial conditions considered within the parameter identification. The arterial behavior outside the measured pressure-range is predicted and shown as the dashed red lines for each condition

Fig. 3

Measured pressure-radius loops and model predictions for subject II. The solid red lines are the model predictions of the three arterial conditions considered within the parameter identification. The arterial behavior outside the measured pressure-range is predicted and shown as the dashed red lines for each condition

Fig. 4

Identified reduced axial force and model prediction for both subjects. The colors red and blue are used for subjects I and II, respectively