Nonlinear viscoelastic properties of collapsible blood vessels

It is shown that the mechanical properties of blood vessels depend on transmural pressure and rate of distortion. In this study, experiments were conducted by applying sinusoidal transmural pressure to vessels and recording the lumen area as a function of arterial pressure and of frequency. Excised canine carotid arteries are subjected to transmural pressures ranging from -30 to 150 mmHg that vary with frequencies of 0.1 Hz, 1 Hz, and 2 Hz. Pressure-Volume (P-V) curves are obtained (fig.) that could be either clockwise (cw), counterclockwise (ccw), or mixed. High pressures and high frequencies hold the artery to the traditionally reported ccw pattern, whereas the lower frequencies operate the cw pattern. The transition between each pattern may cause figure eight relations. Linear viscoelastic models could not explain these results.