Comparative Analysis of Photoplethysmogram (PPG) Waveform Characteristics Across Various Body Sites Under Normal and Apneic Conditions

Detecting sleep apnea through wearable devices poses challenges due to the condition's variability across populations and the inconsistencies in measurements attributed to current wearable technologies. This study aims at comparing photoplethysmogram (PPG) waveform characteristics in healthy subjects, including the change in amplitude, width, and time to peak (Tp) of the signal. PPG signals were recorded at six different body sites (wrist upper, wrist lower, ring finger, thumb, neck, and head) under both simulated normal and apneic conditions. A key objective of this work was to identify optimal LED intensities for detecting these waveform features at each site, providing valuable insights for future development of PPG hardware by pinpointing the most effective intensities. Additionally, the research aims for a better understanding of the variation of the PPG waveform between different body sites.