title: Influence of emphysema distribution on pulmonary function parameters in COPD patients.
abstract: OBJECTIVE
  To evaluate the impact that the distribution of emphysema has on clinical and functional severity in patients with COPD.
  
  
  METHODS
  The distribution of the emphysema was analyzed in COPD patients, who were classified according to a 5-point visual classification system of lung CT findings. We assessed the influence of emphysema distribution type on the clinical and functional presentation of COPD. We also evaluated hypoxemia after the six-minute walk test (6MWT) and determined the six-minute walk distance (6MWD).
  
  
  RESULTS
  Eighty-six patients were included. The mean age was 65.2 ± 12.2 years, 91.9% were male, and all but one were smokers (mean smoking history, 62.7 ± 38.4 pack-years). The emphysema distribution was categorized as obviously upper lung-predominant (type 1), in 36.0% of the patients; slightly upper lung-predominant (type 2), in 25.6%; homogeneous between the upper and lower lung (type 3), in 16.3%; and slightly lower lung-predominant (type 4), in 22.1%. Type 2 emphysema distribution was associated with lower FEV1, FVC, FEV1/FVC ratio, and DLCO. In comparison with the type 1 patients, the type 4 patients were more likely to have an FEV1 < 65% of the predicted value (OR = 6.91, 95% CI: 1.43-33.45; p = 0.016), a 6MWD < 350 m (OR = 6.36, 95% CI: 1.26-32.18; p = 0.025), and post-6MWT hypoxemia (OR = 32.66, 95% CI: 3.26-326.84; p = 0.003). The type 3 patients had a higher RV/TLC ratio, although the difference was not significant.
  
  
  CONCLUSIONS
  The severity of COPD appears to be greater in type 4 patients, and type 3 patients tend to have greater hyperinflation. The distribution of emphysema could have a major impact on functional parameters and should be considered in the evaluation of COPD patients.
authors.affiliation: Centro Hospitalar de São João EPE, Porto, Portugal.
authors.forename: Helder Novais e
authors.initials: HN
authors.lastname: Bastos
authors.affiliation: Centro Hospitalar de São João EPE, Porto, Portugal.
authors.forename: Inês
authors.initials: I
authors.lastname: Neves
authors.affiliation: Centro Hospitalar de São João EPE, Porto, Portugal.
authors.forename: Margarida
authors.initials: M
authors.lastname: Redondo
authors.affiliation: Serviço de Radiologia, Centro Hospitalar de São João EPE, Porto, Portugal.
authors.forename: Rui
authors.initials: R
authors.lastname: Cunha
authors.affiliation: Serviço de Radiologia, Centro Hospitalar de São João EPE, Porto, Portugal.
authors.forename: José Miguel
authors.initials: JM
authors.lastname: Pereira
authors.affiliation: Centro Hospitalar de São João EPE, Porto, Portugal.
authors.forename: Adriana
authors.initials: A
authors.lastname: Magalhães
authors.affiliation: Centro Hospitalar de São João EPE, Porto, Portugal.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Fernandes
mesh_terms: D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008168:Lung / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000473:pathology / Q000503:physiopathology*; D011656:Pulmonary Emphysema / Q000175:diagnosis / Q000473:pathology / Q000503:physiopathology*; D012129:Respiratory Function Tests; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed