Systolic blood pressure accuracy enhancement in the electronic palpation method using pulse waveform

This paper presents and evaluates some methods to improve the accuracy of systolic blood pressure measurements based on the pulse waveform. A set of measurement was carried out with elderly cardiac surgery patients. The experiments comprised two to five measurements per patient, each including a one-minute follow-up, after which the cuff was slowly inflated over the systolic blood pressure. Systolic pressure errors were defined and correlations with other specific values, like pressure rise time, pulse wave velocity, systolic pressure, augmentation, arm circumference and body mass index were calculated. These indices may he affected by arterial stiffness, a common source of errors in blood pressure measurements. With a value of -0.52, the character which correlated best with systolic error was found to be the peak level of the first derivative of the pressure signal. Also rise time (10%...90%) exhibits a moderate correlation, +0.49. On the other hand, pulse wave velocity, body mass index, cardiac output, peripheral and intra-arterial temperature do not seem to correlate with systolic blood pressure error. It is also noteworthy that indices describing the rising edge of the pressure pulse correlated better with systolic pressure error than those describing the failing part. Using the first derivative peak level method, the accuracy improved slightly.