title: The effect of helium and oxygen on exercise performance in chronic obstructive pulmonary disease: a randomized crossover trial.
abstract: BACKGROUND
  Breathing supplemental oxygen reduces breathlessness during exercise in patients with chronic obstructive pulmonary disease (COPD). Replacing nitrogen with helium reduces expiratory flow resistance and may improve lung emptying. Combining these treatments should be independently effective.
  
  
  OBJECTIVE
  Study the effect of changing oxygen or helium concentration in inspired gas during exercise in patients with stable COPD.
  
  
  METHODS
  In 82 patients (mean age, 69.7 yr; mean FEV(1), 42.6% predicted), we measured endurance shuttle walking distance, resting and exercise oxygen saturation, and end-exercise dyspnea (Borg scale) while patients breathed Heliox28 (72% He/28% O(2)), Heliox21 (79% He/21% O(2)), Oxygen28 (72% N(2)/28% O(2)), or medical air (79% N(2)/21% O(2)). Gases were administered using a randomized, blinded, crossover design via a face mask and an inspiratory demand valve.
  
  
  RESULTS
  Breathing Heliox28 increased walking distance (mean+/-SD, 147+/-150 m) and reduced Borg score (-1.28+/-1.30) more than any other gas mixture. Heliox21 significantly increased walking distance (99+/-101 m) and reduced dyspnea (Borg score, -0.76+/-0.77) compared with medical air. These changes were similar to those breathing Oxygen28. The effects of helium and oxygen in Heliox28 were independent. The increase in walking distance while breathing Heliox28 was inversely related to baseline FEV(1) breathing air.
  
  
  CONCLUSIONS
  Reducing inspired gas density can improve exercise performance in COPD as much as increasing inspired oxygen. These effects can be combined as Heliox28 and are most evident in patients with more severe airflow obstruction.
authors.affiliation: Respiratory Medicine, Royal Hallamshire Hospital, Department of General Practice and Primary Care, ScHARR, Biomedical Sciences, University of Sheffield, Sheffield, UK. e.a.laude@sheffield.ac.uk
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Laude
authors.forename: Nicholas C
authors.initials: NC
authors.lastname: Duffy
authors.forename: Chloe
authors.initials: C
authors.lastname: Baveystock
authors.forename: Beatriz
authors.initials: B
authors.lastname: Dougill
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Campbell
authors.forename: Rod
authors.initials: R
authors.lastname: Lawson
authors.forename: Paul W
authors.initials: PW
authors.lastname: Jones
authors.forename: Peter M
authors.initials: PM
authors.lastname: Calverley
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D018592:Cross-Over Studies; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D005541:Forced Expiratory Volume / Q000502:physiology; D006371:Helium / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010102:Oxygen Inhalation Therapy / Q000379:methods*; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology / Q000628:therapy*; D013147:Spirometry; D016896:Treatment Outcome; D016138:Walking / Q000502:physiology
chemical_list: D006371:Helium