Tracking-Cuff System for Beat-to-Beat Recording of Blood Pressure

A system is described for the automatic beat-to-beat tracking of blood pressure (BP) based on the detection of Korotkoff sounds. Upon each detection, a discrete adjustment in cuff pressure is made prior to the next cardiac cycle. In comparison with other continuous tracking systems, digital control allows for estimation of systolic BP based on precise knowledge of cuff pressure at each heart beat. Simultaneous recordings of intra-arterial pressure (radial artery) and systolic pressure measured with the tracking system were made in 4 subjects during 1-min trials of resting, paced respiration, and mental arithmetic. Correlations of the paired measures of intra-arterial and cuff pressure for 27 trials varied from .46 to .90 (median = .72). The standard error of estimate of intra-arterial systolic BP varied from 1.8 to 6.3 mmHg (median = 3.6). The system can be used without discomfort to track systolic BP for 60 and 120 sec in experiments involving repeated cuff inflations. Critical features and advantages of the tracking-cuff system for blood pressure measurement and biofeedback are discussed.