Method for Evaluation of Trustworthiness of Oscillometric Blood Pressure Measurements

Simple, unobtrusive, and reliable estimation of cardiovascular parameters is a challenge. We present a novel, simple, and noninvasive method called Ratio2 that provides expected ranges for systolic and diastolic blood pressure values (SBP, DBP) estimated by any algorithm, and an evaluation of vessel compliance. Ratio2 was developed in the frame of the oscillometric blood pressure estimation and it exploits the equality between the arterial blood pressure and the cuff pressure at the mean arterial pressure (MAP). This method is based on the observation that the brachial arterial blood pressure pulses, with MAP used as baseline, are characterized by a peak to trough ratio close to 2. This ratio is employed to characterize expected ranges for estimates of systolic and diastolic blood pressure. Any SBP or DBP measurement which is not contained in these intervals is deemed untrustworthy, and it is marked as such. Ratio2 also provides parameters that are used in a mathematical model of arterial blood pressure (BP) to evaluate vessel stiffness. We tested the performance of the Ratio2 method on 150 oscillometric recordings and their corresponding Omron BP estimates obtained from 10 healthy subjects. Results are encouraging, whereby, (a) out-of-range values obtained with the maximum amplitude algorithm (MAA) and the maximum/minimum slope algorithm (MMSA) methods were successfully detected, and (b) linear correlation between age and vessel compliance is -85% (p<0.005). Therefore, we conclude that the proposed work shows promise towards providing noninvasive BP monitors with an inbuilt mechanism for assessing the fidelity of their BP estimates along with an indicator of vessel compliance.