title: Idiopathic pulmonary fibrosis: prognostic value of changes in physiology and six-minute-walk test.
abstract: OBJECTIVE
  Idiopathic pulmonary fibrosis is a fatal disease with a variable rate of progression. We hypothesized that changes in distance walked and quantity of desaturation during a six-minute-walk test (6MWT) would add prognostic information to changes in FVC or diffusing capacity for carbon monoxide.
  
  
  METHODS
  One hundred ninety-seven patients with idiopathic pulmonary fibrosis were evaluated. Desaturation during the 6MWT was associated with increased mortality even if a threshold of 88% was not reached. Baseline walk distance predicted subsequent walk distance but was not a reliable predictor of subsequent mortality in multivariate survival models. The predictive ability of serial changes in physiology varied when patients were stratified by the presence/absence of desaturation < or = 88% during a baseline 6MWT. For patients with a baseline saturation < or = 88% during a 6MWT, the strongest observed predictor of mortality was serial change in diffusing capacity for carbon monoxide. For patients with saturation > 88% during their baseline walk test, serial decreases in FVC and increases in desaturation area significantly predicted subsequent mortality, whereas decreases in walk distance and in diffusing capacity for carbon monoxide displayed less consistent statistical evidence of increasing mortality in our patients.
  
  
  CONCLUSIONS
  These data highlight the importance of stratifying patients by degree of desaturation during a 6MWT before attributing prognostic value to serial changes in other physiologic variables.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, University of Michigan Health System, Ann Arbor, MI 48109, USA. flaherty@umich.edu
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Flaherty
authors.forename: Adin-Cristian
authors.initials: AC
authors.lastname: Andrei
authors.forename: Susan
authors.initials: S
authors.lastname: Murray
authors.forename: Chris
authors.initials: C
authors.lastname: Fraley
authors.forename: Thomas V
authors.initials: TV
authors.lastname: Colby
authors.forename: William D
authors.initials: WD
authors.lastname: Travis
authors.forename: Vibha
authors.initials: V
authors.lastname: Lama
authors.forename: Ella A
authors.initials: EA
authors.lastname: Kazerooni
authors.forename: Barry H
authors.initials: BH
authors.lastname: Gross
authors.forename: Galen B
authors.initials: GB
authors.lastname: Toews
authors.forename: Fernando J
authors.initials: FJ
authors.lastname: Martinez
mesh_terms: D000368:Aged; D002248:Carbon Monoxide / Q000378:metabolism; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011379:Prognosis; D011653:Pulmonary Diffusing Capacity; D011658:Pulmonary Fibrosis / Q000401:mortality* / Q000503:physiopathology*; D012189:Retrospective Studies; D012307:Risk Factors; D016019:Survival Analysis; D014797:Vital Capacity
chemical_list: D002248:Carbon Monoxide