The relation of pulse pressure to stroke volume.

Abstract

In 1904 Erlanger and Hooker 1 suggested that the product of the pulse pressure (P. P.) and the pulse rate (P. R.) might be used as an index to the circulation rate (C. R.), or, expressed differently, the pulse pressure as an index to the stroke volume (S. V.), provided changes in systolic time and elasticity of the arteries do not disturb too much the direct relation of the P. P. to S. V.

In order to ascertain what the relation is, four normal individuals were studied under four relatively normal conditions. The conditions studied were the recumbent and standing postures and light and post-heavy exercise. Arterial pressure determinations could not be made during heavy exercise; therefore, they were made immediately afterwards.

The arterial pressure readings were made simultaneously by the oscillatory (Erlanger) and the auscultatory methods. The circulation rate in liters per minute was determined by the Henderson and Haggard 2 method, involving the inhalation of ethyl iodide. Ten arterial pressure determinations were made to each observation of the circulation rate and the average of these are used as a basis of comparison.

When the S. V. is plotted against the P. P. it is found that a straight line passing through the points inaicating the mean values for standing and light exercise almost, if not quite, passes through zero and also the mean of heavy exercise, indicating that the relationship between these is one of direct proportionality. On the other hand the mean of the recumbent observation always falls to the left of this line. The recumbent pulse rate and diastolic pressure are in each case decidedly lower than in the other states. The longer systolic time of the slower P. R. and the reduced coefficient of elasticity associated with the lower diastolic pressure both would have the effect of reducing the P. P. produced by a given stroke volume, and both would, therefore, tend to put the mean of the recumbent reading to the left of the line passing through the mean standing and exercise readings.