New algorithm for automatic determination of systolic and diastolic blood pressures in oscillometric measurements

Most automated non-invasive blood pressure measuring devices are based on some empirically derived criteria applied to the oscillometric index, which is defined as a certain characteristic physical property of pressure pulses measured by an inflated cuff wrapped around the upper arm during cuff pressure deflation. In this study, different algorithms for automatic determination of the systolic and diastolic pressures are compared. In addition to the measured pressure pulses, which are one of a typical physical property used for the oscillometric index, some other properties are applied such as a time derivative and a powered short time variance of the pressure data, as well as the audible part of the data measured by a microphone implanted in the cuff (Korotkoff sounds). Beside known empirical algorithms based on characteristic ratios of the oscillometric pulse amplitude, and the maximum and minimum slope of the oscillometric envelope, a new algorithm is introduced based on the presence and absence of oscillometric activity. This algorithm can be applied either to the powered short time variance of the pressure changes in the cuff or to the Korotkoff sounds.