title: Heliox improves oxygen delivery and utilization during dynamic exercise in patients with chronic obstructive pulmonary disease.
abstract: BACKGROUND
  Normoxic heliox (mixture of 79% He and 21% O(2)) may enhance exercise tolerance in patients with chronic obstructive pulmonary disease (COPD). It remains to be determined whether part of these beneficial effects could be ascribed to increased O(2) delivery (O(2)DEL) to locomotor muscles.
  
  
  OBJECTIVE
  To investigate the effects of heliox on peripheral O(2)DEL and utilization during exercise in moderate to severe COPD.
  
  
  METHODS
  Twelve mildly hypoxic or nonhypoxemic men (FEV(1) = 45.0 +/- 13.0% predicted) underwent constant-work rate tests (70-80% peak) to the limit of tolerance while receiving heliox or room air. Near-infrared spectroscopy determined changes (Delta) in leg muscle deoxygenation (deoxyhemoglobin concentration [HHb], an index of fractional O(2) extraction), and surface electromyography estimated muscle fiber recruitment (n = 5). Q and Sp(O(2)) were monitored by impedance cardiography and pulse oximetry, respectively.
  
  
  RESULTS
  Heliox significantly decreased dynamic hyperinflation and increased exercise tolerance compared with room air (640 +/- 95 s vs. 371 +/- 100 s; P < 0.01). Heliox also accelerated on-exercise dynamics of Q, which were accompanied by faster O(2) uptake kinetics and slower Delta[HHb] responses (P < 0.05). During steady-state exercise, Sp(O(2))-corrected Delta[HHb] values decreased with heliox despite no significant changes in cardiac output. Muscle fiber recruitment and leg effort scores were also diminished (P < 0.05). On a multiple regression analysis, reductions in dynamic hyperinflation, dyspnea, and Delta[HHb] were independently related to improvements in exercise tolerance with heliox (R(2) = 0.91; P < 0.01).
  
  
  CONCLUSIONS
  Heliox increases lower limb O(2)DEL and utilization during dynamic exercise in patients with moderate to severe COPD. These effects enhance exercise tolerance in this patient population.
authors.affiliation: Pulmonary Function and Clinical Exercise Physiology Unit (SEFICE), Division of Respiratory Diseases, Department of Medicine, Federal University of São Paulo (UNIFESP), São Paulo, Brazil.
authors.forename: Gaspar R
authors.initials: GR
authors.lastname: Chiappa
authors.forename: Fernando
authors.initials: F
authors.lastname: Queiroga
authors.forename: Ethiane
authors.initials: E
authors.lastname: Meda
authors.forename: Leonardo F
authors.initials: LF
authors.lastname: Ferreira
authors.forename: Fernando
authors.initials: F
authors.lastname: Diefenthaeler
authors.forename: Marcos
authors.initials: M
authors.lastname: Nunes
authors.forename: Marco A
authors.initials: MA
authors.lastname: Vaz
authors.forename: Maria Christina L
authors.initials: MC
authors.lastname: Machado
authors.forename: Luis Eduardo
authors.initials: LE
authors.lastname: Nery
authors.forename: J Alberto
authors.initials: JA
authors.lastname: Neder
mesh_terms: D000368:Aged; D018592:Cross-Over Studies; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D006371:Helium / Q000008:administration & dosage*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000008:administration & dosage*; D010101:Oxygen Consumption / Q000502:physiology*; D010102:Oxygen Inhalation Therapy / Q000379:methods*; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology / Q000628:therapy*
chemical_list: D006371:Helium; C038949:heliox; D010100:Oxygen