Fig. 7.

Vascular cross-sectional area as a function of transmural blood pressure for the thoracic descending aorta (top two rows) and the carotid artery (bottom two rows). Experimental data are shown in gray; elastic response of each model are shown in black dashed lines; and the corresponding viscoelastic models are shown in solid black lines. Experimental data collected under ex vivo conditions are shown on the first and third rows, and the second and fourth rows show results obtained for in vivo conditions. Note that thoracic descending aorta and carotid artery ex vivo results and thoracic descending aorta in vivo results utilize ovine vessels, while in vivo carotid artery results utilizes human vessels. The results from the Kelvin model are given in the left column, results with the arctangent model are given in the middle column, and results with the sigmoid model are given in the right column. Note that blood-pressure and vessel area oscillations, like those due to valve closure (dicrotic notch) or reflective pressure waves introduce sharp features in the pressure-area plots of the in vivo experimental data. Since the ex vivo experimental measurements are from a single vessel, driven by an artificial pump, these sharp features are not present.