title: Respiratory paradox as an indicator of arousal from non-REM sleep.
abstract: Increasing respiratory effort is the likely stimulus for arousal in patients with sleep-disordered breathing. Changes in the phase angle waveform (an indirect measure of respiratory effort) may provide a useful non-EEG indicator of respiratory-related arousal. The aim of this study was to investigate the relationship between phase angle change (using a continuous measurement technique) and EEG arousal. Polysomnographic sleep recordings (including: EEG, EOG, EMG, respiratory effort [ribcage and abdominal movement], respiratory paradox [continuous phase angle measurement], oral-nasal airflow, and oxygen saturation) were performed in a purpose built laboratory on 30 patients with sleep-disordered breathing (15 patients with obstructive sleep apnoea/hypopnoea syndrome [OSAHS]; 15 chronic heavy snorers without OSAHS) and 15 age and weight matched, non-snoring normal subjects. All data, including the temporal relationship between phase angle change and EEG arousal, were analyzed manually (4,545 phase angle changes and 6,473 EEG arousals). There was a highly significant correlation (p<0.001) between phase angle index (changes/hour of sleep) and EEG arousal index (arousals/hour of sleep). However, mean phase angle index allowed a much clearer differentiation between the three subject groups, with the mean phase angle index providing a six-fold difference between normal and OSAHS groups, while the EEG arousal index gave only a two-fold difference. In support of the suggestion that phase angle changes represent respiratory-related sleep disruption, more than twice as many EEG arousals were associated with a change in the phase angle waveform in patients with sleep-disordered breathing than in normal subjects. This study highlights the limitations of EEG arousal scoring in the assessment of patients with sleep-disordered breathing and provides further evidence to support phase angle change as an indicator of respiratory-related sleep disruption.
authors.affiliation: North West Lung Centre, Wythenshawe Hospital, Manchester, UK.
authors.forename: E J
authors.initials: EJ
authors.lastname: Eaton
authors.forename: K I
authors.initials: KI
authors.lastname: Hume
authors.forename: P A
authors.initials: PA
authors.lastname: Stone
authors.forename: A A
authors.initials: AA
authors.lastname: Woodcock
mesh_terms: D000328:Adult; D001143:Arousal / Q000502:physiology*; D015992:Body Mass Index; D002908:Chronic Disease; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D017286:Polysomnography / Q000379:methods; D012119:Respiration; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis*; D012895:Sleep, REM / Q000502:physiology*