Upper airway muscle responsiveness to rising PCO2 during NREM sleep

Giora Pillar, Atul Malhotra, Robert B. Fogel, Josee Beauregard, David I. Slamowitz, Steven A. Shea, David P. White

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


Although pharyngeal muscles respond robustly to increasing PCO2 during wakefulness, the effect of hypercapnia on upper airway muscle activation during sleep has not been carefully assessed. This may be important, because it has been hypothesized that CO2-driven muscle activation may importantly stabilize the upper airway during stages 3 and 4 sleep. To test this hypothesis, we measured ventilation, airway resistance, genioglossus (GG) and tensor palatini (TP) electromyogram (EMG), plus end-tidal PCO2 (PET(CO2)) in 18 subjects during wakefulness, stage 2, and slow-wave sleep (SWS). Responses of ventilation and muscle EMG to administered CO2 (PET(CO2) = 6 Torr above the eupneic level) were also assessed during SWS (n = 9) or stage 2 sleep (n = 7). PET(CO2) increased spontaneously by 0.8 ± 0.1 Torr from stage 2 to SWS (from 43.3 ± 0.6 to 44.1 ± 0.5 Torr, P < 0.05), with no significant change in GG or TP EMG. Despite a significant increase in minute ventilation with induced hypercapnia (from 8.3 ± 0.1 to 11.9 ± 0.3 l/min in stage 2 and 8.6 ± 0.4 to 12.7 ± 0.4 l/min in SWS, P < 0.05 for both), there was no significant change in the GG or TP EMG. These data indicate that supraphysiological levels of PET(CO2) (50.4 ± 1.6 Torr in stage 2, and 50.4 ± 0.9 Torr in SWS) are not a major independent stimulus to pharyngeal dilator muscle activation during either SWS or stage 2 sleep. Thus hypercapnia-induced pharyngeal dilator muscle activation alone is unlikely to explain the paucity of sleep-disordered breathing events during SWS.

Original languageEnglish (US)
Pages (from-to)1275-1282
Number of pages8
JournalJournal of Applied Physiology
Issue number4
StatePublished - 2000
Externally publishedYes


  • Dilator muscle
  • Genioglossus
  • Hypercapnia
  • Nonrapid eye movement
  • Obstructive sleep apnea syndrome
  • Slow-wave sleep

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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