title: Usefulness of the 6-minute walk test as a screening test for pulmonary arterial enlargement in COPD.
abstract: OBJECTIVE
  Pulmonary hypertension and exercise-induced oxygen desaturation (EID) influence acute exacerbation of COPD. Computed tomography (CT)-detected pulmonary artery (PA) enlargement is independently associated with acute COPD exacerbations. Associations between PA to aorta (PA:A) ratio and EID in patients with COPD have not been reported. We hypothesized that the PA:A ratio correlated with EID and that results of the 6-minute walk test (6MWT) would be useful for predicting the risk associated with PA:A >1.
  
  
  METHODS
  We retrospectively measured lung function, 6MWT, emphysema area, and PA enlargement on CT in 64 patients with COPD. The patients were classified into groups with PA:A ≤1 and >1. Receiver-operating characteristic curves were used to determine the threshold values with the best cutoff points to predict patients with PA:A >1.
  
  
  RESULTS
  The PA:A >1 group had lower forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), FEV1:FVC ratio, diffusion capacity of lung carbon monoxide, 6MW distance, and baseline peripheral oxygen saturation (SpO2), lowest SpO2, highest modified Borg scale results, percentage low-attenuation area, and history of acute COPD exacerbations ≤1 year, and worse BODE (Body mass index, airflow Obstruction, Dyspnea, and Exercise) index results (P<0.05). Predicted PA:A >1 was determined for SpO2during 6MWT (best cutoff point 89%, area under the curve 0.94, 95% confidence interval 0.88-1). SpO2<90% during 6MWT showed a sensitivity of 93.1, specificity of 94.3, positive predictive value of 93.1, negative predictive value of 94.3, positive likelihood ratio of 16.2, and negative likelihood ratio of 0.07.
  
  
  CONCLUSIONS
  Lowest SpO2during 6MWT may predict CT-measured PA:A, and lowest SpO2<89% during 6MWT is excellent for detecting pulmonary hypertension in COPD.
authors.affiliation: Department of Community Health Sciences, Kobe University Graduate School of Health Sciences; Department of Rehabilitation.
authors.forename: Yutaro
authors.initials: Y
authors.lastname: Oki
authors.affiliation: Department of Respiratory Medicine, Kobe City Medical Center West Hospital, Kobe.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kaneko
authors.affiliation: Department of Community Health Sciences, Kobe University Graduate School of Health Sciences.
authors.forename: Yukari
authors.initials: Y
authors.lastname: Fujimoto
authors.affiliation: Department of Rehabilitation.
authors.forename: Hideki
authors.initials: H
authors.lastname: Sakai
authors.affiliation: Department of Community Health Sciences, Kobe University Graduate School of Health Sciences; Department of Rehabilitation.
authors.forename: Shogo
authors.initials: S
authors.lastname: Misu
authors.affiliation: Department of Community Health Sciences, Kobe University Graduate School of Health Sciences; Department of Rehabilitation, Sapporo Nishimaruyama Hospital, Sapporo, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Mitani
authors.affiliation: Department of Community Health Sciences, Kobe University Graduate School of Health Sciences; Department of Rehabilitation.
authors.forename: Takumi
authors.initials: T
authors.lastname: Yamaguchi
authors.affiliation: Department of Community Health Sciences, Kobe University Graduate School of Health Sciences.
authors.forename: Hisafumi
authors.initials: H
authors.lastname: Yasuda
authors.affiliation: Department of Community Health Sciences, Kobe University Graduate School of Health Sciences.
authors.forename: Akira
authors.initials: A
authors.lastname: Ishikawa
mesh_terms: D000368:Aged; D001011:Aorta / Q000000981:diagnostic imaging* / Q000503:physiopathology; D001027:Aortography / Q000379:methods*; D019540:Area Under Curve; D000072226:Computed Tomography Angiography; D017079:Exercise Tolerance; D005260:Female; D005541:Forced Expiratory Volume; D006439:Hemodynamics; D006801:Humans; D007564:Japan; D008168:Lung / Q000098:blood supply* / Q000503:physiopathology*; D008297:Male; D011237:Predictive Value of Tests; D011651:Pulmonary Artery / Q000000981:diagnostic imaging* / Q000503:physiopathology; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000503:physiopathology; D012372:ROC Curve; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014797:Vital Capacity; D000070857:Walk Test
keywords: 6-minute walk test; chronic obstructive pulmonary disease; exercise-induced oxygen desaturation; pulmonary artery