A novel method of estimating small airway disease using inspiratory-to-expiratory computed tomography

Respiration Aug 29, 2017

Kirby M et al. – This study evaluated small airway diseases utilizing a novel computed tomography (CT) inspiratory–to–expiratory approach known as disease probability measure (DPM) and its correlation with pulmonary function. It was observed that pulmonary function and symptoms have a significant correlation with CT inspiratory–to–expiratory gas trapping measurements. However, additional investigations are needed to confirm the quantitative and spatial differences between parametric response map (PRM) and DPM classification.


  • Participants from the CanCOLD study were assessed with full–inspiration/full–expiration CT and pulmonary function measurements.
  • Voxel images were classified based on PRM and DPM as emphysema, gas trapping (GasTrap) related to functional small airway disease, or normal.


  • Participants were classified as never–smokers (n = 135), at risk (n = 97), Global Initiative for Chronic Obstructive Lung Disease I (GOLD I; n = 140), and GOLD II chronic obstructive pulmonary disease (n = 96).
  • PRMGasTrap and DPMGasTrap measurements were significantly elevated in GOLD II versus never–smokers and at risk and in GOLD I versus at risk.
  • Based on DPM classification, the gas trapping measurements were markedly higher in GOLD II versus GOLD I.
  • More voxels were classified as gas trapping by DPM than by PRM.
  • Both DPM and PRMGasTrap measurements were significantly associated with forced expiratory volume in 1 second (FEV1), FEV1/forced vital capacity, residual volume/total lung capacity, bronchodilator response, and dyspnea.

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