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Abstract:
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This study investigates the application of Electroencephalography (EEG ) to detect Sleep disordered breathing (SDB ) using power spectral analysis . A preliminary study was performed on 13 subjects (ages : 49 .08 ± 8 .82 ) previously diagnosed with OSA . Power spectral analysis was performed and centered on apnea /hypopnea event terminations . The normalized power changes between the frequency bands delta , theta , alpha and sigma were calculated using the Welch Averaging Periodogram method between 10 s of EEG data before the event termination and 10 s of EEG data after event termination . A significant decrease in normalized delta power and a significant increase in normalized theta , alpha and sigma power were observed across the event terminations . The values of the differences in the normalized powers were studied and threshold values corresponding to changes in delta , theta , alpha and sigma bands were chosen . Differences in normalized powers equal to or greater than these thresholds were hypothesized to indicate the presence of event terminations . Power spectral changes were calculated across the EEG signal for the entire night duration by the application of two adjacent 10 s sliding windows moved 5s at a time . Normalized power differences across the sliding windows corresponding to values greater than the threshold values of delta and threshold values of either theta /alpha /sigma were scored as event terminations . These detections were then verified with the EEG signal which had been previously scored by a sleep specialist from an accredited sleep lab and who was blind to the objective of this study . The results showed a good sensitivity (r=0 .98 ) but a number of detections not corresponding to apneic /hypopneic events were observed in both OSA and Control group . These are hypothesized to be due to other cortical activity like RERA's (Respiratory effort -related arousal ) , transient arousals or K -complexes /spindles which have similar characteristics to cortical arousals . In conclusion , this method proved to be successful in detecting apneic / hypopneic events but cannot be used as a method to diagnose SDB without further investigation . |