CMIC Group (Japan)

<bold>Background:</bold> Emphysema and overinflation are associated with airflow limitation, but their regional distribution within the lungs is less understood. <bold>Objective:</bold> To examine the association between regional emphysema (LAA-950%), overinflation (expiratory/inspiratory volume ratio) and gas trapping (DPM gas trapping) with FEV₁/FVC. <bold>Methods:</bold> Post-bronchodilator spirometry and HRCT (inspiratory and expiratory) scans were collected in TRAIT, a prospective 3-year observational study. Quantitative HRCT metrics were derived by VIDA software in the upper and lower lobes, and their relationship with FEV₁/FVC was tested using ANCOVA (adjusting for age, height and sex). The strength of these associations was expressed as η². <bold>Results:</bold> Subjects with a smoking history included: ACO (n=85; mean age=70 years; FEV₁, 70% predicted; FEV₁/FVC, 0.58) or COPD (n=104; mean age=71 years; FEV₁, 69% predicted; FEV₁/FVC, 0.55). Upper lobar volumes were slightly greater (≤6%) than lower lobar volumes. More gas-trapping, overinflation and a trend for more emphysema were seen in the upper lobes, but a stronger association between these measures and FEV₁/FVC was seen in the lower lobes (<bold>Table</bold>). <bold>Conclusions:</bold> In this cross-sectional analysis, more structural damage was observed in the upper lobes, but damage in the lower lobes was more strongly associated with airflow limitation, regardless of lobar volume. <fig><object-id>erj;66/suppl_69/OA4434/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig>