Central airway and peripheral lung structures in airway disease-dominant COPD

Naoya Tanabe; Kaoruko Shimizu; Kunihiko Terada; Susumu Sato; Masaru Suzuki; Hiroshi Shima; Akira Oguma; Tsuyoshi Oguma; Satoshi Konno; Masaharu Nishimura; Toyohiro Hirai

doi:10.1183/23120541.00672-2020

Central airway and peripheral lung structures in airway disease-dominant COPD

ERJ Open Res. 2021 Mar 22;7(1):00672-2020. doi: 10.1183/23120541.00672-2020. eCollection 2021 Jan.

Authors

Naoya Tanabe^{1

2}, Kaoruko Shimizu^{3

2}, Kunihiko Terada⁴, Susumu Sato¹, Masaru Suzuki³, Hiroshi Shima¹, Akira Oguma³, Tsuyoshi Oguma¹, Satoshi Konno³, Masaharu Nishimura^{3

5}, Toyohiro Hirai¹

Affiliations

¹ Dept of Respiratory Medicine, Kyoto University Graduate School of Medicine, Kyoto, Japan.
² These authors contributed equally.
³ Dept of Respiratory Medicine, Faculty of Medicine, Hokkaido University, Sapporo, Japan.
⁴ Terada Clinic, Respiratory Medicine and General Practice, Himeji, Japan.
⁵ Hokkaido Institute of Respiratory Diseases, Sapporo, Japan.

Abstract

The concept that the small airway is a primary pathological site for all COPD phenotypes has been challenged by recent findings that the disease starts from the central airways in COPD subgroups and that a smaller central airway tree increases COPD risk. This study aimed to examine whether the computed tomography (CT)-based airway disease-dominant (AD) subtype, defined using the central airway dimension, was less associated with small airway dysfunction (SAD) on CT, compared to the emphysema-dominant (ED) subtype. COPD patients were categorised into mild, AD, ED and mixed groups based on wall area per cent (WA%) of the segmental airways and low attenuation volume per cent in the Kyoto-Himeji (n=189) and Hokkaido COPD cohorts (n=93). The volume per cent of SAD regions (SAD%) was obtained by nonrigidly registering inspiratory and expiratory CT. The AD group had a lower SAD% than the ED group and similar SAD% to the mild group. The AD group had a smaller lumen size of airways proximal to the segmental airways and more frequent asthma history before age 40 years than the ED group. In multivariable analyses, while the AD and ED groups were similarly associated with greater airflow limitation, the ED, but not the AD, group was associated with greater SAD%, whereas the AD, but not the ED, group was associated with a smaller central airway size. The CT-based AD COPD subtype might be associated with a smaller central airway tree and asthma history, but not with peripheral lung pathologies including small airway disease, unlike the ED subtype.