The phase-plane method in the study of blood pressure

A framework for the mathematical modeling of the evolution of pressure with age in humans is presented. It is shown that when pressure changes with respect to times are represented in the phase plane, it becomes clear that the evolution of systolic pressure and that of diastolic pressure have two distinct phases during a lifetime. There exists a critical age before which pressure acceleration is negative. After this critical age, pressure acceleration becomes positive. In both cases, pressure velocity is positive. The point of zero acceleration is the inflexion point on the age-versus pressure curve. The author (1) presents data from national surveys that have been interpreted in the phase plane; (2) shows that these results hold valid across a variety of parameters, including sex and race; and (3) interprets the data in the phase plane to relate them to the effects of cardiovascular disease