title: CT air trapping is independently associated with lung function reduction over time.
abstract: OBJECTIVE
  We aimed to study the association between lung function decline and quantitative computed tomography (CT) air trapping.
  
  
  METHODS
  Current and former heavy smokers in a lung cancer screening trial underwent volumetric low-dose CT in inspiration and expiration. Spirometry was obtained at baseline and after 3 years. The expiratory to inspiratory ratio of mean lung density (E/I-ratioMLD) was used to quantify air trapping. CT emphysema was defined as voxels in inspiratory CT below -950 Hounsfield Unit. Linear mixed modeling was used to determine the association between CT air trapping and lung function.
  
  
  RESULTS
  We included 985 subjects with a mean age of 61.3 years. Independent of CT emphysema, CT air trapping was significantly associated with a reduction in forced expiratory volume in one second (FEV1) and the ratio of FEV1 over the forced vital capacity (FEV1/FVC); FEV1 declines with 33 mL per percent increase in CT air trapping, while FEV1/FVC declines 0.58% per percent increase (both p<0.001). CT air trapping further elicits accelerated loss of FEV1/FVC (additional 0.24% reduction per percent increase; p = 0.014).
  
  
  CONCLUSIONS
  In a lung cancer screening cohort, quantitatively assessed air trapping on low-dose CT is independently associated with reduced lung function and accelerated decline of FEV1/FVC.
authors.affiliation: Radiology, University Medical Center Utrecht, Utrecht, The Netherlands. metsonno@gmail.com
authors.forename: Onno M
authors.initials: OM
authors.lastname: Mets
authors.forename: Pim A
authors.initials: PA
authors.lastname: de Jong
authors.forename: Bram
authors.initials: B
authors.lastname: van Ginneken
authors.forename: Cas L J J
authors.initials: CL
authors.lastname: Kruitwagen
authors.forename: Mathias
authors.initials: M
authors.lastname: Prokop
authors.forename: Matthijs
authors.initials: M
authors.lastname: Oudkerk
authors.forename: Jan-Willem J
authors.initials: JW
authors.lastname: Lammers
authors.forename: Pieter
authors.initials: P
authors.lastname: Zanen
mesh_terms: D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012129:Respiratory Function Tests; D012907:Smoking / Q000009:adverse effects; D013147:Spirometry; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014797:Vital Capacity / Q000502:physiology