Changes in the photoplethysmogram waveform after exercise

Photoplethysmography can be used to estimate vascular compliance and arterial blood oxygen saturation. To ensure accurate measurement in the various applications, it is of interest to study the changes in the photoplethysmogram (PPG) waveform under different conditions. Ten people participated in the study to analyze the changes in the width ratio of the PPG waveform immediately and 20 minutes after vigorous exercise. The width of the PPG waveform at 10%, 30%, 50%, 70%, and 90% amplitude of the pulse are measured and ten combinations of width ratios (WR) are examined. It is found that the group of subjects who performs exercise less frequently in their normal daily life (1.6plusmn1.1 hrs/wk) shows an increase immediately after exercise in seven WRs (significant increase in two WRs, where p = 0.004), but the reverse phenomenon is noticed in the group of subjects who carries out exercise on a more frequent basis (4.3plusmn1.8 hrs/wk, p < 0.03 for seven WRs). Since the amount of regular exercise performed by an individual is often an indication of the properties of one's cardiovascular system, it is therefore suggested that WR could be a representative parameter of it