title: An integrated index combined by dynamic hyperinflation and exercise capacity in the prediction of morbidity and mortality in COPD.
abstract: BACKGROUND
  Dynamic hyperinflation (DH) and exercise limitation develop in patients with COPD; however, there is lack of knowledge about their long-term clinical consequences. We aimed to assess the impact of DH and exercise capacity in predicting mortality and also morbidity, as evaluated  by emergency visits and hospital admissions in COPD patients during a 4-year period.
  
  
  METHODS
  We recruited 73 stable COPD patients. The relationships of different respiratory parameters (FEV(1)%, body mass index, 6 min walk test distance [6MWD], static hyperinflation as measured by  the ratio of inspiratory capacity to total lung capacity (IC/TLC) at rest, DH as measured by the change between the post- and pre-exercise values of IC/TLC [ΔIC/TLC], P(aO(2)), and P(aCO(2))) with emergency visits and hospital admissions because of exacerbations  and also with respiratory and all-cause mortality were assessed.
  
  
  RESULTS
  The median follow-up period was 47 months (IQR 45-48 months, n = 73). During the follow-up there were 8 (11%) deaths. The ΔIC/TLC value was 3.9 ± 4.6%. The Kaplan-Meier survival curve showed  that the cumulative survival rate was significantly lower in the patients with ΔIC/TLC > 4 and with 6MWD ≤ 439.56 m, using these values as thresholds. (The rates for sensitivity were 100% and 87.5%, and for specificity were 56.92% and 87.69%, respectively). The Cox proportional hazards  model showed that DH (hazard ratio = 1.4, 95% CI = 1.09-1.84, P = .009) and 6MWD (hazard ratio = 0.98, 95% CI = 0.97-0.99, P = .006) were independent predictors of all-cause and respiratory mortality. 6MWD, FEV(1)%, IC/TLC, and ΔIC/TLC were found to  be significantly related to emergency visits (r = -0.28, r = -0.41, r = -0.24, and r = 0.38, respectively) and hospital admissions (r = -0.41, r = -0.45, r = -0.36, and r = 0.28, respectively).
  
  
  CONCLUSIONS
  DH and exercise capacity are reliable and independent  predictors for mortality and morbidity in COPD patients. We propose that DH and exercise capacity be considered in the assessment of long-term clinical consequences of COPD patients.
authors.affiliation: Department of Chest Diseases, Mersin University School of Medicine, Mersin, Turkey. eylemozgur@yahoo.com
authors.forename: Eylem Sercan
authors.initials: ES
authors.lastname: Ozgür
authors.forename: Sibel Atiş
authors.initials: SA
authors.lastname: Nayci
authors.forename: Cengiz
authors.initials: C
authors.lastname: Özge
authors.forename: Bahar
authors.initials: B
authors.lastname: Taşdelen
mesh_terms: D000368:Aged; D015992:Body Mass Index; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005541:Forced Expiratory Volume; D006760:Hospitalization; D006801:Humans; D007320:Inspiratory Capacity; D053208:Kaplan-Meier Estimate; D008168:Lung / Q000503:physiopathology*; D008875:Middle Aged; D015999:Multivariate Analysis; D016016:Proportional Hazards Models; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000401:mortality / Q000503:physiopathology*; D012372:ROC Curve; D012720:Severity of Illness Index; D013147:Spirometry; D016138:Walking / Q000502:physiology