title: Distance and oxygen desaturation during the 6-min walk test as predictors of long-term mortality in patients with COPD.
abstract: BACKGROUND
  The distance walked in the 6-min walk test (6MWT) predicts mortality in patients with severe COPD. Little is known about its prognostic value in patients with a wider range of COPD severity, living in different countries, and the potential additional impact of oxygen desaturation measured during the test.
  
  
  METHODS
  We enrolled 576 stable COPD outpatients in Spain and the United States and observed them for at least 3 years (median, 60 months). We measured FEV1, body mass index, Pao2, Charlson comorbidity score, 6-min walk distance (6MWD), and oxygen saturation by pulse oximetry (Spo2) during the 6MWT. Desaturation was defined as a fall in Spo2 > or = 4% or Spo2 < 90%. Regression analysis helped determine the association between these variables and all-cause and respiratory mortality.
  
  
  RESULTS
  The 6MWD was a good predictor of all-cause and respiratory mortality primarily in patients with FEV1 < 50% of predicted (p < 0.001) after adjusting for all covariates. Patients with desaturation during the 6MWT had a higher mortality rate than patients without desaturation (67% vs 38%, p < 0.001). Oxygen desaturation predicted mortality (relative risk, 2.63; 95% confidence interval, 1.53 to 4.51; p < 0.001) but with less power than Pao2 at rest.
  
  
  CONCLUSIONS
  The 6MWD helps predict mortality primarily in patients with severe COPD. Although the oxygen desaturation profile during the 6MWT improves the predictive ability of the 6MWD, it appears to be of less relevance than in other lung diseases and than the resting Pao2.
authors.affiliation: Pulmonary Department, Hospital La Candelaria, Tenerife. Electronic address: ccasanova@canarias.org.
authors.forename: Ciro
authors.initials: C
authors.lastname: Casanova
authors.affiliation: Pulmonary Division, Bay Pines VA Medical Center, St. Petersburg, FL.
authors.forename: Claudia
authors.initials: C
authors.lastname: Cote
authors.affiliation: Research Unit, Hospital La Candelaria, Tenerife.
authors.forename: José M
authors.initials: JM
authors.lastname: Marin
authors.affiliation: Pulmonary Division. Caritas-St. Elizabeth's Medical Center, Boston, MA.
authors.forename: Víctor
authors.initials: V
authors.lastname: Pinto-Plata
authors.affiliation: Pulmonary Department, Hospital Miguel Servet, Zaragoza, Spain.
authors.forename: Juan P
authors.initials: JP
authors.lastname: de Torres
authors.affiliation: Research Unit, Hospital La Candelaria, Tenerife.
authors.forename: Armando
authors.initials: A
authors.lastname: Aguirre-Jaíme
authors.affiliation: Pulmonary Division. Caritas-St. Elizabeth's Medical Center, Boston, MA.
authors.forename: Carlos
authors.initials: C
authors.lastname: Vassaux
authors.affiliation: Pulmonary Division. Caritas-St. Elizabeth's Medical Center, Boston, MA.
authors.forename: Bartolome R
authors.initials: BR
authors.lastname: Celli
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology*; D011237:Predictive Value of Tests; D029424:Pulmonary Disease, Chronic Obstructive / Q000378:metabolism / Q000401:mortality* / Q000503:physiopathology*; D012720:Severity of Illness Index; D013030:Spain; D015996:Survival Rate; D014481:United States; D016138:Walking / Q000502:physiology*