Sympathetic chemoreflex responses in obstructive sleep apnea and effects of continuous positive airway pressure therapy

Chest. 2007 May;131(5):1406-13. doi: 10.1378/chest.06-2580.


Background: Sympathetic nerve activity is increased in awake and regularly breathing patients with obstructive sleep apnea (OSA). Over time, repetitive hypoxic stress could alter sympathetic chemoreflex function in OSA.

Methods: We determined the responses to acute hypoxia (fraction of inspired oxygen of 0.1, for 5 min), static handgrip exercise, and the cold pressor test (CPT) in 24 patients with OSA (age, 50 +/- 3 years [mean +/- SEM]; apnea-hypopnea index, 47 +/- 6 events per hour) and in 14 age- and weight-matched nonapneic control subjects. Muscle sympathetic nerve activity (MSNA) [peroneal microneurography], BP, and ventilation were monitored.

Results: Basal MSNA was higher in OSA patients compared to control subjects (45 +/- 4 bursts per minute vs 33 +/- 4 bursts per minute, respectively; p < 0.05). Furthermore, compared to control subjects, the MSNA responses to hypoxia were markedly enhanced in OSA (p < 0.001). Whereas the ventilatory responses to hypoxia tended to be increased in OSA (p = 0.06), the BP responses did not differ between the groups (p = 0.45). The neurocirculatory reflex responses to handgrip exercise and to the CPT were similar in the two groups (p = not significant). In OSA patients who were retested after 1 to 24 months of continuous positive airway pressure (CPAP) therapy (n = 11), basal MSNA (p < 0.01) and the responses of MSNA to hypoxia (p < 0.01) decreased significantly, whereas the ventilatory responses remained unchanged (p = 0.82).

Conclusion: These data suggest that the sympathetic responses to hypoxic chemoreflex stimulation are enhanced in OSA and may normalize in part following CPAP therapy.

Publication types

  • Controlled Clinical Trial
  • Research Support, N.I.H., Extramural

MeSH terms

  • Blood Pressure / physiology
  • Carbon Dioxide / metabolism
  • Chemoreceptor Cells / physiopathology*
  • Cold Temperature
  • Continuous Positive Airway Pressure*
  • Female
  • Hand Strength / physiology
  • Heart Rate / physiology
  • Humans
  • Hypoxia / physiopathology
  • Male
  • Middle Aged
  • Muscles / innervation
  • Oxyhemoglobins / metabolism
  • Sleep Apnea, Obstructive / physiopathology*
  • Sleep Apnea, Obstructive / therapy*
  • Sympathetic Nervous System / physiopathology*
  • Tidal Volume / physiology


  • Oxyhemoglobins
  • Carbon Dioxide