The effect of the lability (resilience) of the arterial wall on the blood pressure and pulse curve.–II

Abstract

In a paper published in the 'Proceedings of the Royal Society,' 1913, B, vol. 86, p. 180, Russell Wells and Leonard Hill brought forward evidence to show that the nature of the arterial wall has an important effect in modifying the conduction of the pressure waves from the heart to those arteries where the pulse is usually explored, such, for example, as the radial, where sphygmograms are recorded and readings of arterial pressure taken with the sphygmomanometer. They concluded that the conduction depends on the greater or less "resilience" of the arterial wall, using the term "resilience" to express "the ease with which an elastic tube distends with a rise and recoils with a fall of pressure of the contained fluid"; thus a rubber tube with a wall of 0.2 mm. thick is more "resilient" than one with a wall 0.4mm, thick, the thinner, more "resilient" tube yields with the rise and recoils with the fall of pressure more than the "harder," thicker-walled tube. A glass tube, in this sense, has no resilience, and the same may be said of rubber pressure tubing. As the arterial wall contains muscle, its "resilience" will be altered by a more or less contracted state, also since the degree of contraction and "resilience" may vary locally it is to be expected that the curve of blood-pressure may likewise vary, e. g. in the brachial and in the femoral arteries. We have found this to the case under certain conditions, namely, in cases of aortic regurgitation. In such cases the systolic pressure reading for the leg is much higher, 100mm. or more, than in the arm arteries. Also in normal men a difference in the systolic pressure in the two radial arteries my be observed when the heart is made to beat forcibly by a short period of hard water. The artery relaxed by heat gives the lower systolic pressure. Russell Wells constructed a schema by means of which a know rhythmically changing pressure could be passed (1) through rubber tubes of the same calibre, but varying thickness, e. g. 0.8, 0.4, 0.2 mm., (2) through various lengths of the same tube, (3) through the same tube and same length of tube, but with increasing amplitude.