title: Six-minute walk distance in patients with severe end-stage COPD: association with survival after inpatient pulmonary rehabilitation.
abstract: OBJECTIVE
  To evaluate the relationship between the 6-minute walk distance (6MWD) and survival in a cohort of patients with severe end-stage chronic obstructive pulmonary disease (COPD) who received inpatient pulmonary rehabilitation (IPR) from 1995 to 2007.
  
  
  METHODS
  We retrospectively analyzed 815 patients with severe end-stage COPD who received IPR. 6MWDs before and after IPR (pre-6MWD, post-6MWD) were compared to assess whether 6MWD was significantly changed after IPR. The Kaplan-Meier survival curves were constructed to show the relationship between survival and 6MWD. The age- and or comorbidities-adjusted Cox proportional hazard model was applied to assess association between the survival and the pre-6MWD, post-6MWD, or difference in 6MWD from the pre-6MWD to post-6MWD (Delta6MWD).
  
  
  RESULTS
  Baseline demographics demonstrated a median age 74.0 years, mostly women (60.1%), and white (89.9%) patients with significant comorbid diseases who were most recently hospitalized in acute care facilities (95.1%). IPR significantly increased the 6MWD (mean distance change: 86.4 m; 95% confidence interval [CI], 81.5-91.3 m). Pre-6MWD was not significantly associated with survival. However, post-6MWD was significantly associated with age- and comorbidity-adjusted survival (post-6MWD hazard ratio = 1.336; 95% CI, 1.232-1.449 [post-6MWD x m relative to post-6MWD 2x m]), and Delta6MWD was also significantly associated with age-, comorbidities-, and pre-6MWD-adjusted survival (Delta6MWD hazard ratio = 1.337; 95% CI, 1.227-1.457 [Delta6MWD x m relative to Delta6MWD 2x m]).
  
  
  CONCLUSIONS
  In patients with severe end-stage COPD, IPR significantly improved 6MWD, and the post-6MWD and Delta6MWD were positively associated with the length of survival.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, School of Medicine, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Kyle
authors.initials: K
authors.lastname: Enfield
authors.forename: Sally
authors.initials: S
authors.lastname: Gammon
authors.forename: Jennifer
authors.initials: J
authors.lastname: Floyd
authors.forename: Cassandra
authors.initials: C
authors.lastname: Falt
authors.forename: James
authors.initials: J
authors.lastname: Patrie
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Platts-Mills
authors.forename: Jonathon D
authors.initials: JD
authors.lastname: Truwit
authors.forename: Y Michael
authors.initials: YM
authors.lastname: Shim
mesh_terms: D000367:Age Factors; D000368:Aged; D015331:Cohort Studies; D015897:Comorbidity; D015444:Exercise; D005080:Exercise Test; D005260:Female; D006760:Hospitalization; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D009788:Occupational Therapy; D026741:Physical Therapy Modalities; D016016:Proportional Hazards Models; D029424:Pulmonary Disease, Chronic Obstructive / Q000401:mortality* / Q000534:rehabilitation*; D012189:Retrospective Studies; D012720:Severity of Illness Index; D016138:Walking