Discrete Wavelet Transform-Based Method for Automatic Evaluation of Sleep-Disordered Breathing Using Photoplethysmography

This study proposed the discrete wavelet transform (DWT)-based method for automatic evaluation of sleep-disordered breathing (SDB) in patients with sleep apnea-hypopnea syndrome using photoplethysmography (PPG). The method is based on the fact that the amplitude and pulse rate waveform of PPG reflect vasodilation and vasoconstriction generated by autonomic nervous system (ANS). Thus the amplitude and pulse rate waveform were induced from PPG and they were applied to DWT based on the Coiflet 3 wavelet with order 7. The apnea-hypopnea index (AHI) induced by the proposed method was compared with that measured by a sleep technician. Fifteen patients were participated in this study and correlation statistics revealed significantly high correlation coefficient, indicating good to excellent validity (r = 0.97, p <;<; 0.001). This study indicated that the proposed simple method would be useful in sleep monitoring system and may provide clinical insights when the designing a portable and inexpensive sleep monitoring system.