Quantitative airway evaluation using supine and upright computed tomography in patients with non-cystic fibrosis bronchiectasis and nontuberculous mycobacterial pulmonary disease.

INTRODUCTION

Bronchiectasis, closely associated with nontuberculous mycobacterial pulmonary disease (NTM-PD), exhibits unevenly distributed lesions, yet their spatial features remain unclear. We hypothesized that upright CT, which may better depict distal airways due to gravity-induced lung expansion, might more accurately reflect disease severity and its relationship with pulmonary function tests (PFTs).

METHODS

In this prospective study, twenty patients underwent low-dose inspiratory and expiratory CT scans in standing and supine positions. Airways were segmented with Vincent® software and classified as bronchiectatic or non-bronchiectatic. Generation-specific quantitative CT (QCT) parameters, including inspiratory airway total area (ITA), inspiratory airway lumen area (ILA), wall thickness, and wall area percentage (WA%), were measured and correlated with PFTs.

RESULTS

Bronchiectatic lesions were primarily identified in the 8th-10th generation airways (anatomically the 7th-9th generations), the transition from distal bronchi to proximal bronchioles. Standing CT detected more distal airways than supine CT. Mixed-effect models revealed significantly larger ITA and higher WA% in bronchiectatic airways (8th-10th generations) on standing CT. In non-bronchiectatic airways (trachea to 6th generation), ITA and ILA were significantly larger in the standing position, except for the main bronchus ITA. ITA, ILA, and WA% were moderate to strongly correlated with %FVC, %FEV1, and FEF25-75%, reflecting airway obstruction, with stronger correlations in the standing position. ITA in bronchiectatic airways was moderately negatively correlated with diffusing capacity of the lungs for carbon monoxide, indicating potential alveolar disease.

CONCLUSION

Upright CT offers useful structural biomarkers associated with airflow limitation and possible alveolar impairment in bronchiectasis with NTM-PD.

REGISTRATION: University Hospital Medical Information Network (UMIN 000026587). URL: https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000030456.