title: Supplemental oxygen effect on hypoxemia at moderate altitude in patients with COPD.
abstract: BACKGROUND
  Altitude exposure will cause moderate to severe hypoxemia in patients with chronic obstructive pulmonary disease (COPD). Supplemental oxygen can be used to attenuate this hypoxemia; however, individual response is variable and difficult to predict. The aim of this study was to assess the efficacy of oxygen supplementation in patients with COPD at a barometric pressure similar to that of a commercial aircraft cabin.
  
  
  METHODS
  Following sea-level (40 m) arterial blood gases measurements, 18 patients with COPD were driven to altitude (2086 m), where blood gases were repeated at rest and while on 2 L x min(-1) of supplementary oxygen (altitude O2).
  
  
  RESULTS
  Ascent from sea level to altitude caused significant hypoxemia (75 +/- 9 vs. 51 +/- 6 mmHg), which was partially reversed by supplemental oxygen (64 +/- 9 mmHg). Oxygen supplementation did not significantly alter PaCO2 levels (vs. altitude PaCO2). There was a significant relationship between the sea-level CaO2 versus the altitude O2 CaO2 (r = 0.89, P < 0.001). There was a significant relationship (r = 0.81, P < 0.001) between altitude-induced desaturation and resaturation with the administration of oxygen. There was a significant negative correlation (r = -0.74, P < 0.001) between baseline K(CO) and the improvement in CaO2 with the administration of oxygen.
  
  
  CONCLUSIONS
  Low-flow supplemental oxygen during acute altitude exposure will partially reverse altitude-induced hypoxemia in patients with COPD. Patients with diffusion impairments are likely to experience the greatest altitude desaturation, but will gain the most benefit from supplemental oxygen. Supplemental oxygen, delivered at 2 L x min(-1), should maintain clinically acceptable oxygenation during commercial air travel in patients with COPD.
authors.affiliation: Respiratory Physiology Laboratory, Christchurch Hospital, Christchurch, New Zealand. paul.kelly@cdhb.govt.nz
authors.forename: Paul T
authors.initials: PT
authors.lastname: Kelly
authors.forename: Maureen P
authors.initials: MP
authors.lastname: Swanney
authors.forename: Josh D
authors.initials: JD
authors.lastname: Stanton
authors.forename: Chris
authors.initials: C
authors.lastname: Frampton
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Peters
authors.forename: Lutz E
authors.initials: LE
authors.lastname: Beckert
mesh_terms: D000337:Aerospace Medicine; D000368:Aged; D000531:Altitude; D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000097:blood; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D000860:Hypoxia / Q000503:physiopathology / Q000628:therapy*; D008297:Male; D010100:Oxygen / Q000097:blood; D010102:Oxygen Inhalation Therapy; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D012129:Respiratory Function Tests
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen