Noninvasive method for determining blood pressure and contours of arterial and volume pulses

Abstract

A noninvasive method for monitoring blood pressure, based on the principles established by Riva-Rocci and Korotkoff (K), is described; it furnishes, after a single compression-deflation cycle of the arm-encircling cuff, values of systolic and diastolic blood pressures as well as the contours of the brachial arterial pulse and the corresponding volume pulse. K-sounds are detected by a single microphone situated in the cubital fossa, and the time-varying cuff pressure P(t) is read by a piezoresistive pressure sensor. The behavior of P(t) during deflation is resolved into two parts, P(t)=p(t)+b(t); p is a train of positive going pulses (arising from arterial pulsations), whereas b is a slowly changing baseline. Noise pulses in the microphone output are rejected by using the observation that the first few K-sounds are emitted when p is close to a maximum, and the last few when dp/dt is close to a maximum. The performance of the instrument is illustrated by showing how it copes with ambient noise and involuntary manual perturbations of P and by presenting contours of various pulses.