title: Short-term Effects of Supplemental Oxygen on 6-Min Walk Test Outcomes in Patients With COPD: A Randomized, Placebo-Controlled, Single-blind, Crossover Trial.
abstract: BACKGROUND
  The acute effect of supplemental oxygen during exercise has been shown to differ largely among patients with COPD. It is unknown what factors influence oxygen response.
  
  
  METHODS
  In a randomized, single-blind fashion, 124 patients with COPD underwent one 6-min walk test on supplemental oxygen (6MWTO2) and one 6-min walk test on room air after a practice 6-min walk test. Both gases were delivered via standard nasal prongs (2 L/min). For analyses, patients were stratified on the basis of PaO2values and compared: (1) 34 patients with resting hypoxemia (HYX); (2) 43 patients with exercise-induced hypoxemia (EIH); and (3) 31 patients with normoxemia (NOX).
  
  
  RESULTS
  Oxygen supplementation resulted in an increase in the 6-min walk distance in the total cohort (27 ± 42 meters; P < .001) and in the subgroups of HYX (37 ± 40 meters; P < .001) and EIH (28 ± 44 meters; P < .001) but not in the NOX subgroup (15 ± 43 meters; P = .065). Forty-two percent of patients with HYX and 47% of patients with EIH improved their 6-min walk distance to a clinically relevant extent (≥ 30 meters) by using oxygen. These oxygen responders were characterized by significantly lower 6-min walk distance using room air compared with patients without a relevant response (306 ± 106 meters vs 358 ± 113 meters; P < .05). Although oxygen saturation was significantly higher during 6MWTO2compared with the 6-min walk test on room air in all 3 subgroups, it dropped to < 88% during 6MWTO2in 73.5% of patients with HYX.
  
  
  CONCLUSIONS
  In contrast to patients with NOX, patients with HYX and EIH generally benefit from supplemental oxygen by increasing exercise capacity. However, less than one-half of patients reached the threshold of clinically relevant improvements. These oxygen responders were characterized by significantly lower exercise capacity levels.
  
  
  BACKGROUND
  ClinicalTrials.gov; No.: NCT00886639; URL: www.clinicaltrials.gov.
authors.affiliation: Department of Respiratory Medicine and Pulmonary Rehabilitation, Schoen Klinik Berchtesgadener Land, Schoenau am Koenigssee, Germany. Electronic address: ijarosch@schoen-kliniken.de.
authors.forename: Inga
authors.initials: I
authors.lastname: Jarosch
authors.affiliation: Department of Respiratory Medicine and Pulmonary Rehabilitation, Schoen Klinik Berchtesgadener Land, Schoenau am Koenigssee, Germany; Department for Prevention, Rehabilitation and Sports Medicine, Klinikum Rechts der Isar, Technical University of Munich, Munich, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Gloeckl
authors.affiliation: Department of Pneumology and Critical Care Medicine, University of Marburg, Marburg, Germany.
authors.forename: Eva
authors.initials: E
authors.lastname: Damm
authors.affiliation: Department of Pneumology and Critical Care Medicine, University of Marburg, Marburg, Germany.
authors.forename: Anna-Lena
authors.initials: AL
authors.lastname: Schwedhelm
authors.affiliation: Department of Pneumology and Critical Care Medicine, University of Marburg, Marburg, Germany.
authors.forename: David
authors.initials: D
authors.lastname: Buhrow
authors.affiliation: Department of Pneumology and Critical Care Medicine, University of Marburg, Marburg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Jerrentrup
authors.affiliation: Department of Research and Education, CIRO+, Center of Expertise for Chronic Organ Failure, Horn, the Netherlands; REVAL-Rehabilitation Research Center, BIOMED-Biomedical Research Institute, Faculty of Medicine and Life Sciences, Hasselt University, Diepenbeek, Belgium; Department of Respiratory Medicine, Maastricht University Medical Centre, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht, The Netherlands.
authors.forename: Martijn A
authors.initials: MA
authors.lastname: Spruit
authors.affiliation: Department of Respiratory Medicine and Pulmonary Rehabilitation, Schoen Klinik Berchtesgadener Land, Schoenau am Koenigssee, Germany; Department of Pulmonary Rehabilitation, University of Marburg, Marburg, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Kenn
mesh_terms: D000368:Aged; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010102:Oxygen Inhalation Therapy / Q000379:methods*; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology* / Q000628:therapy*; D012720:Severity of Illness Index; D016037:Single-Blind Method; D016896:Treatment Outcome; D000070857:Walk Test
keywords: 6-min walking distance; COPD; exercise testing; exercise-induced hypoxemia; supplemental oxygen