title: Predicting the need for supplemental oxygen during airline flight in patients with chronic pulmonary disease: a comparison of predictive equations and altitude simulation.
abstract: BACKGROUND
  Patients with chronic pulmonary diseases are at increased risk of hypoxemia when travelling by air. Screening guidelines, predictive equations based on ground level measurements and altitude simulation laboratory procedures have been recommended for determining risk but have not been rigorously evaluated and compared.
  
  
  OBJECTIVE
  To determine the adequacy of screening recommendations that identify patients at risk of hypoxemia at altitude, to evaluate the specificity and sensitivity of published predictive equations, and to analyze other possible predictors of the need for in-flight oxygen.
  
  
  METHODS
  The charts of 27 consecutive eligible patients referred for hypoxia altitude simulation testing before flight were reviewed. Patients breathed a fraction of inspired oxygen of 0.15 for 20 min. This patient population was compared with the screening recommendations made by six official bodies and compared the partial pressure of arterial oxygen (PaO(2)) obtained during altitude simulation with the PaO(2) predicted by 16 published predictive equations.
  
  
  RESULTS
  Of the 27 subjects, 25% to 33% who were predicted to maintain adequate oxygenation in flight by the British Thoracic Society, Aerospace Medical Association or American Thoracic Society guidelines became hypoxemic during altitude simulation. The 16 predictive equations were markedly inaccurate in predicting the PaO(2) measured during altitude simulation; only one had a positive predictive value of greater than 30%. Regression analysis identified PaO(2) at ground level (r=0.50; P=0.009), diffusion capacity (r=0.56; P=0.05) and per cent forced expiratory volume in 1 s (r=0.57; P=0.009) as having predictive value for hypoxia at altitude.
  
  
  CONCLUSIONS
  Current screening recommendations for determining which patients require formal assessment of oxygen during flight are inadequate. Predictive equations based on sea level variables provide poor estimates of PaO(2) measured during altitude simulation.
authors.affiliation: University Health Network, Toronto Western Hospital, Toronto, Ontario.
authors.forename: Ana C
authors.initials: AC
authors.lastname: Bradi
authors.forename: Marie E
authors.initials: ME
authors.lastname: Faughnan
authors.forename: Matthew B
authors.initials: MB
authors.lastname: Stanbrook
authors.forename: Eva
authors.initials: E
authors.lastname: Deschenes-Leek
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Chapman
mesh_terms: D000337:Aerospace Medicine; D000368:Aged; D000369:Aged, 80 and over; D000401:Aircraft; D000531:Altitude; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000097:blood / Q000209:etiology / Q000517:prevention & control*; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D008954:Models, Biological; D010100:Oxygen / Q000008:administration & dosage / Q000097:blood*; D011237:Predictive Value of Tests; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood / Q000150:complications*; D012129:Respiratory Function Tests; D012189:Retrospective Studies; D014195:Travel
chemical_list: D010100:Oxygen
references.citation: Am Rev Respir Dis. 1984 Dec;130(6):980-6
references.pmid: 6508019
references.citation: Thorax. 2003 Aug;58(8):729-32
references.pmid: 12885996
references.citation: Aviat Space Environ Med. 2004 Oct;75(10):905-12
references.pmid: 15497372
references.citation: N Engl J Med. 1984 May 10;310(19):1218-21
references.pmid: 6709028
references.citation: Eur Respir J. 2000 Aug;16(2):214-9
references.pmid: 10968494
references.citation: Chest. 1995 Feb;107(2):352-7
references.pmid: 7842760
references.citation: Ann Intern Med. 1989 Sep 1;111(5):362-7
references.pmid: 2764404
references.citation: Eur Respir J. 2004 Jun;23(6):932-46
references.pmid: 15219010
references.citation: QJM. 2007 Jun;100(6):361-7
references.pmid: 17525132
references.citation: Aviat Space Environ Med. 2006 Nov;77(11):1143-7
references.pmid: 17086767
references.citation: Thorax. 2004 Nov;59(11):966-70
references.pmid: 15516473
references.citation: Am J Respir Crit Care Med. 1995 Dec;152(6 Pt 1):1956-60
references.pmid: 8520762
references.citation: Chest. 2008 Apr;133(4):920-6
references.pmid: 17989155
references.citation: Thorax. 2002 Apr;57(4):289-304
references.pmid: 11923546
references.citation: Eur Respir J. 2000 Jan;15(1):128-30
references.pmid: 10678633
references.citation: Ann Intern Med. 1989 Sep 1;111(5):349-51
references.pmid: 2669590
references.citation: Can Respir J. 1998 Mar-Apr;5(2):95-100
references.pmid: 9707451
references.citation: Aviat Space Environ Med. 2003 May;74(5 Suppl):A1-19
references.pmid: 12817610
references.citation: Chest. 1993 Feb;103(2):422-5
references.pmid: 8432131
references.citation: Eur Respir J. 2000 Apr;15(4):635-9
references.pmid: 10780752
references.citation: Eur Respir J. 2005 Apr;25(4):725-30
references.pmid: 15802350
references.citation: Surg Gynecol Obstet. 1973 Jan;136(1):49-53
references.pmid: 4682262
references.citation: Eur Respir J. 2002 Aug;20(2):300-5
references.pmid: 12212959