title: Changes in the endurance shuttle walk test in COPD patients with chronic respiratory failure after pulmonary rehabilitation: the minimal important difference obtained with anchor- and distribution-based method.
abstract: BACKGROUND
  Although the endurance shuttle walk test (ESWT) has proven to be responsive to change in exercise capacity after pulmonary rehabilitation (PR) for COPD, the minimally important difference (MID) has not yet been established. We aimed to establish the MID of the ESWT in patients with severe COPD and chronic hypercapnic respiratory failure following PR.
  
  
  METHODS
  Data were derived from a randomized controlled trial, investigating the value of noninvasive positive pressure ventilation added to PR. Fifty-five patients with stable COPD, GOLD stage IV, with chronic respiratory failure were included (mean (SD) FEV1 31.1 (12.0) % pred, age 62 (9) y). MID estimates of the ESWT in seconds, percentage and meters change were calculated with anchor based and distribution based methods. Six minute walking distance (6MWD), peak work rate on bicycle ergometry (Wpeak) and Chronic Respiratory Questionnaire (CRQ) were used as anchors and Cohen's effect size was used as distribution based method.
  
  
  RESULTS
  The estimated MID of the ESWT with the different anchors ranged from 186-199 s, 76-82% and 154-164 m. Using the distribution based method the MID was 144 s, 61% and 137 m.
  
  
  CONCLUSIONS
  Estimates of the MID for the ESWT after PR showed only small differences using different anchors in patients with COPD and chronic respiratory failure. Therefore we recommend using a range of 186-199 s, 76-82% or 154-164 m as MID of the ESWT in COPD patients with chronic respiratory failure. Further research in larger populations should elucidate whether this cut-off value is also valid in other COPD populations and with other interventions.
  
  
  BACKGROUND
  ClinicalTrials.Gov (ID NCT00135538).
authors: Wytske A
authors: WA
authors: Altenburg
authors: Marieke L
authors: ML
authors: Duiverman
authors: Nick H T
authors: NH
authors: Ten Hacken
authors: Huib A M
authors: HA
authors: Kerstjens
authors: Mathieu H G
authors: MH
authors: de Greef
authors: Peter J
authors: PJ
authors: Wijkstra
authors: Johan B
authors: JB
authors: Wempe
mesh_terms: D000368:Aged; D001642:Bicycling; D005080:Exercise Test / Q000379:methods*; D017079:Exercise Tolerance; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D006935:Hypercapnia / Q000175:diagnosis / Q000503:physiopathology / Q000534:rehabilitation; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D063087:Noninvasive Ventilation; D011237:Predictive Value of Tests; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000503:physiopathology / Q000534:rehabilitation*; D015203:Reproducibility of Results; D012131:Respiratory Insufficiency / Q000175:diagnosis* / Q000503:physiopathology / Q000534:rehabilitation*; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D013997:Time Factors; D017211:Treatment Failure; D014797:Vital Capacity; D016138:Walking