The Effects of Aging and Degenerative Vascular Disease on the Measurement of Arterial Rigidity in Man*

progressive loss of aortic distensibility with aging (1). Their observations on the pressure-volume relationship in segments of human aortas from five age groups are shown in Figure 1. The curves which represent the less distensible older aortas have a greater slope (d P/d V). The slope of each curve is not fixed, however, and it changes by bending toward the pressure axis as pressure increases. The rate of this change in slope (or the curvature) also is greater in the curves of older aortas. The present report deals with an indirect clini-cal index of the curvature of arterial pressure-volume curves, using the ratio of the change in pulse pressure to the change in diastolic pressure