Dynamic Reactions Produced by Deflating a Blood Pressure Cuff

Intra-arterial pressure was recorded at various points in the compressed segment of brachial artery during deflation of a standard blood pressure cuff in human subjects with arms of normal girth. Cuff pressure and the Korotkoff sounds also were recorded simultaneously. The data were analyzed in terms of the various dynamic reactions produced by cuff deflation, which may influence the auscultatory indications of systolic and diastolic blood pressure. Cuff pressure was incompletely transmitted to the compressed arterial segment. As a result, muffling, the auscultatory indication of diastolic pressure, occurred at a cuff pressure higher than the directly recorded intra-arterial diastolic blood pressure. The first Korotkoff sound, on the other hand, provided a close approximation of intra-arterial systolic pressure. This may be due to a delay in penetration of the diminutive pulse waves into the distal part of the compressed arterial segment at systolic levels of cuff pressure. This effect appears to compensate for other influences tending to raise the indirect reading of systolic blood pressure. The extent of the delay in penetration should be dependent on the length of the collapsed segment, which in turn is a function of cuff width.