Radiographic lung volumes predict progression to COPD in smokers with preserved spirometry in SPIROMICS

We examined whether CT-derived lung volumes representing air trapping could predict adverse respiratory outcomes and more rapid decline in spirometry to overt COPD using mixed-effect linear modelling. Among these subjects with normal forced expiratory volume in 1 s (FEV1) to forced vital capacity (FVC) ratio, CT-measured residual volume (RVCT) to total lung capacity (TLCCT) ratio varied widely, from 21% to 59%. Over 2.5±0.7 years of follow-up, subjects with higher RVCT/TLCCT had a greater differential rate of decline in FEV1/FVC; those in the upper RVCT/TLCCT tertile had a 0.66% (95% CI 0.06%–1.27%) faster rate of decline per year compared with those in the lower tertile (p=0.015) regardless of demographics, baseline spirometry, respiratory symptoms score, smoking status (former versus current) or smoking burden (pack–years). Accordingly, subjects with higher RVCT/TLCCT were more likely to develop spirometric COPD (OR 5.7 (95% CI 2.4–13.2) in upper versus lower RVCT/TLCCT tertile; p<0.001). Other CT indices of air trapping showed similar patterns of association with lung function decline; however, when all CT indices of air trapping, emphysema, and airway disease were included in the same model, only RVCT/TLCCT retained its significance. Increased air trapping based on radiographic lung volumes predicts accelerated spirometry decline and progression to COPD in smokers without obstruction.
Source: European Respiratory Journal - Category: Respiratory Medicine Authors: Tags: Original Articles: COPD Source Type: research