title: Genioglossal muscle response to CO2 stimulation during NREM sleep.
abstract: OBJECTIVE
  The objective was to evaluate the responsiveness of upper airway muscles to hypercapnia with and without intrapharyngeal negative pressure during non-rapid eye movement (NREM) sleep and wakefulness.
  
  
  METHODS
  We assessed the genioglossal muscle response to CO2 off and on continuous positive airway pressure (CPAP) (to attenuate negative pressure) during stable NREM sleep and wakefulness in the supine position.
  
  
  METHODS
  Laboratory of the Sleep Medicine Division, Brigham and Women's Hospital.
  
  
  METHODS
  Eleven normal healthy subjects.
  
  
  METHODS
  During wakefulness and NREM sleep, we measured genioglossal electromyography (EMG) on and off CPAP at the normal eupneic level and at levels 5 and 10 mm Hg above the awake eupneic level.
  
  
  RESULTS
  We observed that CO2 could increase upper-airway muscle activity during NREM sleep and wakefulness in the supine position with and without intrapharyngeal negative pressure. The application of nasal CPAP significantly decreased genioglossal EMG at all 3 levels of PETCO2 during NREM sleep (13.0 +/- 4.9% vs. 4.6 +/- 1.6% of maximal EMG, 14.6 +/- 5.6% vs. 7.1 +/- 2.3% of maximal EMG, and 17.3 +/- 6.3% vs. 10.2 +/- 3.1% of maximal EMG, respectively). However, the absence of negative pressure in the upper airway did not significantly affect the slope of the pharyngeal airway dilator muscle response to hypercapnia during NREM sleep (0.72 +/- 0.30% vs. 0.79 +/- 0.27% of maximal EMG per mm Hg PCO2, respectively, off and on CPAP).
  
  
  CONCLUSIONS
  We conclude that both chemoreceptive and negative pressure reflex inputs to this upper airway dilator muscle are still active during stable NREM sleep.
authors: Department of Thoracic Medicine, Chang Gang Memorial Hospital, Taipei, Taiwan. lyulun@partners.org
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