Expiratory flow-limitation and heliox breathing in resting and exercising COPD patients

Respir Physiol Neurobiol. 2009 Dec 31;169(3):291-6. doi: 10.1016/j.resp.2009.09.009. Epub 2009 Sep 19.


In 26 stable patients with chronic obstructive pulmonary disease, tidal expiratory flow-limitation (TEFL), inspiratory capacity, breathing pattern and dyspnea sensation were assessed during air and heliox (20% O(2) in He) breathing at rest and during exercise up to 2/3 maximal work rate. Breathing air, the 13 patients with TEFL at rest remained flow-limited also during exercise, while 7 of the non-flow-limited patients became flow-limited; tidal volume increased more in non-flow-limited patients, whereas inspiratory capacity decreased in flow-limited and increased in the non-flow-limited patients. Heliox did not abolish flow-limitation, had no effect on breathing pattern, reduced exercise dynamic hyperinflation in 25% of the flow-limited patients, depending on the degree of the dynamic hyperinflation on air, and lessened dyspnea sensation in all patients. Hence, the presence of TEFL has no systematic effects on the respiratory response to heliox, and the heliox-induced decrease of exercise dyspnea is not mainly due to changes in dynamic hyperinflation or TEFL.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Administration, Inhalation
  • Aged
  • Blood Gas Analysis / methods
  • Exercise / physiology*
  • Exhalation / drug effects
  • Exhalation / physiology*
  • Helium / administration & dosage*
  • Humans
  • Inspiratory Capacity / drug effects
  • Inspiratory Capacity / physiology
  • Middle Aged
  • Oxygen / administration & dosage*
  • Pulmonary Disease, Chronic Obstructive / physiopathology*
  • Pulmonary Disease, Chronic Obstructive / therapy*
  • Pulmonary Gas Exchange / drug effects
  • Pulmonary Ventilation / drug effects
  • Pulmonary Ventilation / physiology
  • Respiratory Function Tests / methods
  • Rest / physiology*


  • Helium
  • heliox
  • Oxygen