title: Exercise outcomes after pulmonary rehabilitation depend on the initial mechanism of exercise limitation among non-oxygen-dependent COPD patients.
abstract: OBJECTIVE
  Pulmonary rehabilitation (PR) that includes exercise training can improve exercise tolerance and quality of life for patients with COPD. However, the degree of benefit from PR is variable. We hypothesized that the exercise response to PR varies depending on the initial factors that limit exercise.
  
  
  METHODS
  We retrospectively analyzed the change in exercise capacity after PR in 290 nonhypoxemic patients with COPD. We classified patients into the following subgroups based on the primary limitation seen on initial exercise testing: (1) ventilatory-limited (VL); (2) cardiovascular-limited (CVL); (3) mixed ventilatory/cardiovascular-limited (VLCVL); and (4) non-cardiopulmonary-limited (NL). We compared outcomes among subgroups.
  
  
  RESULTS
  In the entire study population, PR led to increased timed walk distance (30.3%; p < 0.0001) and maximal oxygen consumption (VO2max) [84.8 mL/min; p < 0.0001]. Stepwise multiple regression selected age, ventilatory reserve at peak exercise, and exercise arterial oxygen pressure as individual predictors of improvement in VO2max. VO2max increased in the VL subgroup (30.4 mL/min; p = 0.008), the CVL subgroup (109.0 mL/min; p < 0.0001), the mixed VLCVL subgroup (61.3 mL/min; p < 0.0001), and NL subgroups (110.5 L/min; p < 0.0001). The improvement in VO2max was greater in the CVL subgroup than in the VL subgroup (p < 0.0001). Timed walk distance improved to a similar degree in all subgroups (26 to 36%).
  
  
  CONCLUSIONS
  Patients with nonventilatory exercise limitations experience the greatest increase in VO2max after PR. However, even patients with severe ventilatory limitation can improve exercise tolerance with PR.
authors.affiliation: Department of Pulmonary and Critical Care Medicine, Duke University Medical Center, Durham, NC, USA.
authors.forename: John F
authors.initials: JF
authors.lastname: Plankeel
authors.forename: Barbara
authors.initials: B
authors.lastname: McMullen
authors.forename: Neil R
authors.initials: NR
authors.lastname: MacIntyre
mesh_terms: D000368:Aged; D045422:Continuous Positive Airway Pressure; D005081:Exercise Therapy; D017079:Exercise Tolerance; D005260:Female; D005541:Forced Expiratory Volume; D006304:Health Status; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D029424:Pulmonary Disease, Chronic Obstructive / Q000534:rehabilitation*; D012189:Retrospective Studies; D013147:Spirometry