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.

Methods

• 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.

Results

• 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.