title: Breathing helium-hyperoxia and tolerance of partitioned exercise in patients with COPD.
abstract: OBJECTIVE
  Partitioning exercise by 1-legged cycling is more effective than conventional training in patients with chronic obstructive pulmonary disease. Similarly, inhaling helium-hyperoxia can extend conventional exercise tolerance. This study aimed to determine whether breathing helium-hyperoxia could increase the tolerance of a high-intensity exercise session achieved by 1-legged cycling.
  
  
  METHODS
  Participants completed 2 high-intensity, constant power, 1-legged cycle tests to intolerance (tlimit). In a randomized order, they inspired 40% oxygen with the balance helium via mask and 1-way valve, 1-legged helium-hyperoxia (1L-HH), or room air with supplemental oxygen via a nasal cannula, 1-legged nitrogen-hyperoxia (1L-NH). We assessed quadriceps fatigue from the change in maximal voluntary contraction (FMVC) and transcutaneously stimulated twitch force (Ftwitch).
  
  
  RESULTS
  Fifteen participants (forced expiratory volume in 1 second [SD] = 36 [18]% predicted; forced expiratory volume in 1 second/forced vital capacity = 34 [14]%; peak oxygen uptake = 12.8 [2.9] mL · kg · min) completed the study. Self-reported "leg fatigue" was a reason for stopping 25 of 30 tests. There was no significant difference in tlimit (0.2 [-1.4 to 1.8] min) between 1L-HH (12.2 [5.2] min) and 1L-NH (12.0 [4.1] min), or in FMVC measured shortly after HH and NH tests (P= .09). The Ftwitch was less after exercise (P< .05) in both conditions, without a difference between conditions (P= .46).
  
  
  CONCLUSIONS
  Inspiring a helium-hyperoxia mixture does not increase the endurance of what would be a typical training session, breathing supplemental oxygen, of high-intensity 1-legged constant power exercise. Leg muscle fatigue was similar after 1-legged exercise with and without breathing the helium mixture.
authors.affiliation: Department of Respiratory Medicine (Mr Dolmage and Drs Evans, Brooks, and Goldstein) and Respiratory Diagnostic and Evaluation Services (Mr Dolmage and Dr Goldstein), West Park Healthcare Centre, Toronto, Canada; Department of Infection, Immunity and Inflammation, Leicester University, Leicester, UK (Dr Evans); and Department of Physical Therapy (Drs Brooks and Goldstein) and Department of Medicine (Drs Evans and Goldstein), University of Toronto, Toronto, Canada.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Dolmage
authors.forename: Rachael A
authors.initials: RA
authors.lastname: Evans
authors.forename: Dina
authors.initials: D
authors.lastname: Brooks
authors.forename: Roger S
authors.initials: RS
authors.lastname: Goldstein
mesh_terms: D000368:Aged; D001944:Breath Tests / Q000379:methods; D005080:Exercise Test / Q000379:methods; D017079:Exercise Tolerance; D005260:Female; D006371:Helium / Q000008:administration & dosage*; D006801:Humans; D007866:Leg / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D018763:Muscle Fatigue / Q000502:physiology*; D010100:Oxygen / Q000008:administration & dosage*; D010102:Oxygen Inhalation Therapy / Q000379:methods*; D014677:Pharmaceutical Vehicles / Q000008:administration & dosage; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000188:drug therapy / Q000503:physiopathology; D012129:Respiratory Function Tests / Q000379:methods; D016896:Treatment Outcome
chemical_list: D014677:Pharmaceutical Vehicles; D006371:Helium; D010100:Oxygen