Second Derivative of Photoplethysmography for Estimating Vascular Aging

Coronary artery disease (CAD) is one of the major causes of death. Therefore recurrent monitoring of arterial condition is important. The photoplethysmography (PPG) is simple and cost effective technique to measure blood volume change. As an application of PPG technique, the second derivative of photoplethysmography(SDPTG) was introduced for monitoring arterial condition. SDPTG consists of an a, b, c and d wave in systole and an e wave in diastole. The SDPTG wave pattern is determined by the proportions of the b, c, d, and e waves to the a wave. In the present study, it is confirmed that the b/a ratio and SDPTG-AI increased with age, and the c/a, d/a, and e/a ratios decreased with age. The informal method which substitutes formal SDPTG-AI was suggested.