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Thorax 62:799-805 doi:10.1136/thx.2006.072488
  • Sleep-disordered breathing

Influence of wakefulness on pharyngeal airway muscle activity

  1. Yu-Lun Lo1,
  2. Amy S Jordan1,
  3. Atul Malhotra1,
  4. Andrew Wellman1,
  5. Raphael A Heinzer2,
  6. Matthias Eikermann1,
  7. Karen Schory1,
  8. Louise Dover1,
  9. David P White1
  1. 1Sleep Disorders Research Program, Brigham and Women’s Hospital, Boston, MA, USA
  2. 2Service de Pneumologie, Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne, Switzerland
  1. Correspondence to:
    Dr Yu-Lun Lo
    Brigham and Women’s Hospital, Sleep Disorders Research Program, 75 Francis Street, Boston, Massachusetts 02115, USA; lyulun{at}partners.org
  • Received 28 September 2006
  • Accepted 7 February 2007
  • Published Online First 27 March 2007

Abstract

Background: Whether loss of wakefulness itself can influence pharyngeal dilator muscle activity and responsiveness is currently unknown. A study was therefore undertaken to assess the isolated impact of sleep on upper airway muscle activity after minimising respiratory/mechanical inputs.

Methods: Ten healthy subjects were studied. Genioglossus (GG), tensor palatini (TP) and diaphragm (DIA) electromyography (EMG), ventilation and sleep-wake status were recorded. Non-invasive positive pressure ventilation was applied. Expiratory pressure was adjusted to yield the lowest GGEMG, thereby minimising airway negative pressure (mechanoreceptor) effects. Inspiratory pressure, respiratory rate and inspiratory time were adjusted until the subjects ceased spontaneous ventilation, thereby minimising central respiratory input. Muscle activity during wakefulness, wake-sleep transitions, stable non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep were evaluated in the supine position.

Results: In transitions from wakefulness to sleep, significant decrements were observed in both mean GGEMG and TPEMG (1.6 (0.5)% to 1.3 (0.4)% of maximal GGEMG; 4.3 (2.3)% to 3.7 (2.1)% of maximal TPEMG). Compared with sleep onset, the activity of TP during stable NREM sleep and REM sleep was further decreased (3.7 (2.1)% vs 3.0 (2.0)% vs 3.0 (2.0)% of maximal EMG). However, GGEMG was only further reduced during REM sleep (1.3 (0.4)% vs 1.0 (0.3)% vs 1.1 (0.4)% of maximal EMG).

Conclusion: This study suggests that wakefulness per se, independent of respiratory/mechanical stimuli, can influence pharyngeal dilator muscle activity.

Footnotes

  • Published Online First 27 March 2007

  • This study was supported by NIH grants R01 HL48531, P50 HL60292, NCRR GCRC RR01032 and National Institute of Aging AG024837-01.

  • Competing interests: None.