This article proposes an ECG-referenced comb filter design for PPG signals and analyses its influence on the measurement of PD50.
As explained above, PD50 is measured between the ECG signal R-peak and the 50% PPG signal raising front level.
It is expected that PD50 is an average of the two consecutive recurrences PD50.
It means that the PD50, measured from the comb filtered signal, is an average over r recurrences and delayed by half of the r recurrences.
In addition to the procedure described, test signals were generated in MATLAB to analyse the influence of the comb filter on the PD50 measurement.
The second generator input is PD50 that determines the PPG signal raising front delay from the R-peak for each generated recurrence (Fig.
In the next step, the PD50 was measured by using a raw generated signal and PPG signals filtered with comb filters.
In the case of a sharp PD50 change, the reaction time for the adaptive comb filter with six recurrences averaging is longer than for the adaptive comb filter with recurrences averaging, as it was discussed above.
To show influence of the comb filter on the PD50 measurement, the PPG and ECG signals were recorded while the subject was carrying out the Valsalva maneuver .
In the next step, the PD50 was measured between the ECG signal R peaks and the PPG signal raising fronts.
Inverse PD50 should be taken as relative blood pressure.
Also, the inverse PD50 shift is visible between the signals in Figs.