Incompressibility of the human arterial wall: an in vitro ultrasound study

The assumption that the arterial wall behaves like incompressible material simplifies the analysis of arterial wall elasticity. Experimental evidence for the incompressibility assumption has been obtained directly by volume-displacement and radiological methods. Recent developments in ultrasound technology have made it possible to take direct, high-resolution measurements of the internal diameter and wall thickness of an artery and thus calculate the cross-sectional area of the arterial wall. The objective of this study was to determine the cross-sectional area of the arterial wall in vitro at different levels of strain in order to demonstrate the incompressibility assumption.

Two different types of fresh, human, medium-sized arteries were studied, the internal mammary artery, and a less elastic and more muscular artery, the radial artery. The internal diameter and wall thickness were measured with an ultrasonic echo-tracking device (NIUS 1; Asulab, Neuchâtel, Switzerland) over 1-min steps of increasing intra-arterial pressure (0, 50, 100, 150 and 175 mmHg).

The cross-sectional area of the arterial wall of the radial and internal mammary artery remained unchanged under different levels of strain.

Since the artery length remained constant during the pressure increases, the lack of change in the cross-sectional area of the arterial wall suggests that the arterial wall of human medium-sized arteries is essentially incompressible.