Respiratory paradox as an indicator of arousal from non-REM sleep

• Published in: Sleep (New York, N.Y.) Vol. 22; no. 8; pp. 1059 - 1065
• Main Authors: EATON, E. J, HUME, K. I, STONE, P. A, WOODCOCK, A. A
• Format: Journal Article
• Language: English
• Published: Rochester, MN American Academy of Sleep Medicine 15.12.1999
• Subjects: Adult; Arousal - physiology; Biological and medical sciences; Body Mass Index; Chronic Disease; Electroencephalography; Female; Humans; Male; Medical sciences; Non tumoral diseases; Otorhinolaryngology. Stomatology; Polysomnography - methods; Respiration; Sleep Apnea, Obstructive - diagnosis; Sleep, REM - physiology; Upper respiratory tract, upper alimentary tract, paranasal sinuses, salivary glands: diseases, semeiology; Human; Respiratory tract; Vigilance; Sleep apnea syndrome; Methodology; Investigation method; Sleep disorder; ENT disease; Respiratory movement; Obstruction; Indicator
• ISSN: 0161-8105; 1550-9109
• DOI: 10.1093/sleep/22.8.1059

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.