The Patterns of the Arterial Pressure Pulse

During the past ten years there have accumulated in this laboratory a large number of records of the arterial pressure pulses taken with the Hypodermic Manometer (4). These are faithful records of the changes in the pressure of the blood in various arteries of man and of other animals. The form of the pressure pulse curve is quite variable. Some of the types are drawn roughly to scale in the figures presented herewitOh, but, there are many intergrading examples which can not be shown for lack of space. It is the purpose of this paper t,o describe the manner in which these typical patterns tlake form and to present a simple hypothesis that will account physically for t,he variations seen in the pressure pulses in different arteries and under differ-ent? conditions. The simplest pulse form is that seen in very small animals such as the mouse, canary, frog or turtle (1). During early systole the ejection from the heart is rapid, blood is coming into the arterial tree faster than it is leaving through the arterioles and the pressure in the arteries rises abruptly. Later the rate of ejection falls, the arterial pressure rise continues but becomes less abrupt. Toward the end of systole there is a balance between the rate of ejection and the rate of arteriolar drainage. The curve is then horizontal. An actual decline in the curve is sometlimes seen during late systole, when ejection falls to a rate that is less than arteriolar drainage. During diastole the curve is a perfectly smooth fall of pressure with time. falls faster at first when the pressure is high. It Blood drains out of the arterioles more rapidly and each unit of blood leaving the arterioles makes a greater pressure diff'erence when the pressure is high than when the pressure is low. This smooth pressure curve is the simple consequence of filling and emptying of the aiterial compression chamber. However it is seen only in small animals. The t,inv arteries of these creatures respond so quickly that tlhey follow faithfully t,he pressure changes which are produced by the heart. In ordinary laboratory animals such as the dog and in man the form of the pressure pulse is much more complex. Superimposed upon the first described filling and emptying curve are waves of arterial origin. This is because the mass of the arberial blood column is so large and the …