Significantly Reduced Blood Pressure Measurement Variability for Both Normotensive and Hypertensive Subjects: Effect of Polynomial Curve Fitting of Oscillometric Pulses

Figure 2

Illustration of the determination of corresponding timings for SBP, DBP, and MAP calculations. Two automatic techniques were used (without polynomial curve fitting: purely relied on the originally recorded oscillometric pulse peak amplitude; with curve fitting: based on the 6th-order polynomial curve fitting of the oscillometric pulse peaks). The thresholds of characteristic ratio of 0.5 and 0.7 are given with horizontal dashed lines. Automated SBP and DBP (without curve fitting) are calculated from the cuff pressures associated with the first and last oscillometric pulses whose normalised amplitude is larger than 0.5 and 0.7, respectively. Automated SBP and DBP (with curve fitting) are calculated from the cuff pressures associated with the thresholds (0.5 and 0.7) crossing the fitted polynomial curve. denotes the pulses with normalised peak amplitude larger than a threshold (0.5 for SBP, 0.7 for DBP, and 1.0 for MAP).