title: Quantitative computed tomography assessment of air trapping in relapsing polychondritis: correlations with spirometric values.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the relationship between quantitative computed tomography (CT) parameters of air trapping obtained with inspiratory and expiratory CT and pulmonary function tests (PFTs) in patients with relapsing polychondritis (RP).
  
  
  METHODS
  This study included 23 patients with RP who underwent both CT and PFTs. In each patient, the mean lung density (MLD) was obtained by averaging CT attenuation of the lung parenchyma on both inspiratory and expiratory CT. The ratio of expiratory MLD to inspiratory MLD (E/I ratio) was also calculated. Correlations between those quantitative CT measurements and the results of PFTs were evaluated using Spearman rank correlation.
  
  
  RESULTS
  The expiratory MLD and E/I ratio were significantly correlated with forced expiratory volume in 1 second (FEV1) %predicted, ratio of FEV1 to FVC (FEV1/FVC), and the mid expiratory phase of forced expiratory flow (FEF25%-75%) %predicted (expiratory MLD: FEV1 %predicted, r = 0.764, P < 0.0001; FEV1/FVC, r = 0.764, P < 0.0001; FEF25%-75% %predicted, r = 0.674, P < 0.001, respectively; the E/I ratio: FEV1 %predicted, r = -0.689, P < 0.001; FEV1/FVC, r = -0.689, P < 0.001; FEF25%-75% %predicted, r = -0.586, P < 0.01, respectively). The correlation between inspiratory MLD and PFTs did not reach statistical significance.
  
  
  CONCLUSIONS
  In RP patients, air trapping demonstrated on expiratory CT correlated with airway obstruction. This study may assist further refinement of the use of CT as quantitative evaluation for small and large airway obstruction in RP.
authors.affiliation: From the *Department of Radiology, †Division of Respiratory and Infectious Diseases, Department of Internal Medicine, St Marianna University School of Medicine, Kawasaki, Kanagawa, Japan.
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Matsushita
authors.forename: Shin
authors.initials: S
authors.lastname: Matsuoka
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Yamashiro
authors.forename: Atsuko
authors.initials: A
authors.lastname: Fujikawa
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Kurihara
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Yagihashi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Handa
authors.forename: Teruomi
authors.initials: T
authors.lastname: Miyazawa
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Nakajima
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000388:Air; D045853:Exhalation; D005260:Female; D006801:Humans; D001239:Inhalation; D008297:Male; D008875:Middle Aged; D011081:Polychondritis, Relapsing / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D012129:Respiratory Function Tests; D012189:Retrospective Studies; D013147:Spirometry; D014057:Tomography, X-Ray Computed / Q000379:methods*; D055815:Young Adult