For statistical analysis, we simultaneously have to measure the BP value from a cuff-based BP machine to get the regression coefficients (a, b, c, d).
Coefficients are calculated using a statistical technique called Linear Regression. Once the coefficients are obtained, we will obtain a new PWV (pulse wave velocity) value from the ECG and PPG data. Using the below equation, we calculate the NIBP value:
Systolic BP (SBP) = a*(PWV) + b
Diastolic BP ( DBP) = c*(PWV) + d
A simple flow graph of getting coefficients is as shown below: