Distensibility

Distensibility is a metric of the stiffness of blood vessels. It is defined as

$$D = \frac{d_{sys}-d_{dias}}{(p_{sys}-p_{dias})d_{dias}}$$,

where $$d_{sys}$$ and $$d_{dias}$$ are the diameter of the vessel in systole and diastole, and $$p_{sys}$$and $$p_{dias}$$are the systolic and diastolic blood pressure.