Effect of oxygen in obstructive sleep apnea: role of loop gain

Respir Physiol Neurobiol. 2008 Jul 31;162(2):144-51. doi: 10.1016/j.resp.2008.05.019. Epub 2008 Jun 3.


We compared the effect of oxygen on the apnea-hypopnea index (AHI) in six obstructive sleep apnea patients with a relatively high loop gain (LG) and six with a low LG. LG is a measure of ventilatory control stability. In the high LG group (unstable ventilatory control system), oxygen reduced the LG from 0.69+/-0.18 to 0.34+/-0.04 (p<0.001) and lowered the AHI by 53+/-33% (p=0.04 compared to the percent reduction in the low LG group). In the low LG group (stable ventilatory control system), oxygen had no effect on LG (0.24+/-0.04 on room air, 0.29+/-0.07 on oxygen, p=0.73) and very little effect on AHI (8+/-27% reduction with oxygen). These data suggest that ventilatory instability is an important mechanism causing obstructive sleep apnea in some patients (those with a relatively high LG), since lowering LG with oxygen in these patients significantly reduces AHI.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Airway Resistance / physiology
  • Algorithms
  • Case-Control Studies
  • Cheyne-Stokes Respiration / complications
  • Cheyne-Stokes Respiration / therapy
  • Feedback / physiology
  • Female
  • Humans
  • Male
  • Middle Aged
  • Models, Biological
  • Oxygen / administration & dosage*
  • Polysomnography
  • Positive-Pressure Respiration / methods*
  • Pulmonary Ventilation / physiology*
  • Reference Values
  • Respiratory Mechanics / physiology*
  • Severity of Illness Index
  • Sleep Apnea, Obstructive / complications
  • Sleep Apnea, Obstructive / physiopathology
  • Sleep Apnea, Obstructive / therapy*
  • Treatment Outcome


  • Oxygen