The variation of arterial elasticity with blood pressure in man (Part I)

Abstract

In a recent paper (1) Bramwell and A. V. Hill showed that the velocity of the pulse wave is a measure of the elasticity of the arteries, according to the formula: Velocity = 3.57 / √ Percentage increase in volume per (in metres per sec.) mm. Hg. increase of pressure. They showed also, both from the data of Roy (2), and by direct measurement on an isolated artery, that the pressure of fluid inside an artery plays an important part in modifying the velocity of the pulse wave, the velocity increasing as a function of the rise in pressure. In other words, the extensibility of an artery decreases as the pressure inside it is increased, a phenomenon analogous to the well-known fact that the extensibility of a muscle decreases as the tension on it is increased. This fact is of some importance in man, since, the more extensible the arteries are, the less is the work required of the heart and the more regular is the flow of blood in the capillaries. The velocity of the pulse wave may be measured with accuracy in man by the use of a hot wire sphygmograph (3) (4) and the relative extensibility of the arteries then calculated from the above formula.