Figure 4.

Raw PPG waveform data processing procedures, steps, and analysis methods. The original PPG waveform first needs to remove the DC component and the baseline component that causes the signal drift. Then, the noise is removed by moving the average method and then dividing the waveform to obtain individual pulse waveforms. If there is only a single peak, the second derivative function must be obtained, the position of the corresponding second peak must be found, and then the value of R-PTT can be calculated. The highest and second peaks are directly calculated for waveforms with more than two peaks. The distance of the high peak is the required R-PTT. Next, the blood pressure value corresponding to each pulse wave can be calculated using the R-PTT with the correction parameters calculated from the user’s initial blood pressure value input. Finally, the calculated blood pressure value is compared with the invasive blood pressure value to verify the algorithm’s accuracy.