Infrared and red PPG signals analysis of the healthy subjects and clinical patients

A lab-made photoplethysmographic (PPG) device was applied to measure PPG signals of healthy cohorts and selected patients by medical doctors for arterial elasticity assessment. The off-line analysis on vascular health was done afterwards using a commercial software. The received information is repeatable and reproducible, however, sometimes not unambiguous. Temporal parameters of the signal components were studied in order to define the invariants by means of optimal envelope construction. After PPG pulse series normalization the series were twice differentiated and the maxima (A) and minima (B) of the second order derivative PPGs (SDPPG) were determined. The constructed graphs of the ratios B/A as a function of time were produced for the healthy compared with the vascular patients. Also principal component analysis (PCA) was used in decomposing the PPG signal for finding functional relationships between components. The 30-points moving averages were calculated for B/A value series of each SDPPG signals which is presented as the result. The B/A index shows higher values for the finger arteries compared the toe arteries. The infrared based B/A index values were higher than the red based B/A index values, and finger B/A index values were higher than toe B/A index values. The main goal for this study the noninvasive method for arterial elasticity assessment based on clinical and volunteer measurements with PPG & SDPPG means.