title: Six minute walk distance is a predictor of survival in patients with chronic obstructive pulmonary disease undergoing pulmonary rehabilitation.
abstract: BACKGROUND
  Chronic obstructive pulmonary disease (COPD) is a progressive and distressing disease with a trajectory that is often difficult to predict.
  
  
  OBJECTIVE
  To determine whether initial 6 min walk distance (6MWD) or change in 6MWD following inpatient pulmonary rehabilitation (PR) predicted survival.
  
  
  METHODS
  Patients referred for PR in 2010 were studied in a retrospective chart review. Measures of 6MWD before and following PR were recorded. Initial 6MWD was categorized as ≥250 m, 150 m to 249 m and ≤149 m. Government databases provided survival status up until December 2013 and survival analyses were performed. Initial 6MWD and a minimally important difference (MID) of ≥30 m were used for survival analysis.
  
  
  RESULTS
  The cohort consisted of 237 patients (92 men, 145 women) with severe COPD. Mean (± SD) forced expiratory volume in 1 s (FEV1) was 0.75±0.36 L, with a mean FEV1/forced vital capacity (FVC) ratio of 0.57±0.16. Overall three-year survival was 58%. Mean survival for the study period as per predefined categories of 6MWD of ≥250 m, 150 m to 249 m and ≤149 m was 42.2, 37.0 and 27.8 months (P<0.001), respectively, with a three-year survival of 81%, 66% and 34% observed, respectively. Overall mean change in 6MWD was 62±57 m, and a minimal improvement of ≥30 m was observed in 72% of patients. In the lowest walking group, early mortality was significantly higher among those who did not achieve minimal improvement. Older age, male sex and shorter initial 6MWD were negative predictors of survival.
  
  
  CONCLUSIONS
  In patients with severe COPD, initial 6MWD was predictive of survival. Overall survival at three years was only 58% and was especially poor (34%) in patients with low (<150 m) initial walk distance.
authors.forename: Esther
authors.initials: E
authors.lastname: Dajczman
authors.forename: Rima
authors.initials: R
authors.lastname: Wardini
authors.forename: Goulnar
authors.initials: G
authors.lastname: Kasymjanova
authors.forename: David
authors.initials: D
authors.lastname: Préfontaine
authors.forename: Marc Alexander
authors.initials: MA
authors.lastname: Baltzan
authors.forename: Norman
authors.initials: N
authors.lastname: Wolkove
mesh_terms: D000368:Aged; D015331:Cohort Studies; D005080:Exercise Test; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D029424:Pulmonary Disease, Chronic Obstructive / Q000401:mortality / Q000503:physiopathology / Q000534:rehabilitation*; D012138:Respiratory Therapy; D012189:Retrospective Studies; D015996:Survival Rate; D016896:Treatment Outcome; D014797:Vital Capacity