Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto, 606-8507, Japan.
Respir Res. 2019 Apr 18;20(1):77. doi: 10.1186/s12931-019-1047-5.
Decreased airway lumen size and increased lung volume are major structural changes in chronic obstructive pulmonary disease (COPD). However, even though the outer wall of the airways is connected with lung parenchyma and the mechanical properties of the parenchyma affect the behaviour of the airways, little is known about the interactions between airway and lung sizes on lung function and symptoms. The present study examined these effects by establishing a novel computed tomography (CT) index, namely, airway volume percent (AWV%), which was defined as a percentage ratio of the airway tree to lung volume.
Inspiratory chest CT, pulmonary function, and COPD Assessment Tests (CAT) were analysed in 147 stable males with COPD. The whole airway tree was automatically segmented, and the percentage ratio of the airway tree volume in the right upper and middle-lower lobes to right lung volume was calculated as the AWV% for right lung. Low attenuation volume % (LAV%), total airway count (TAC), luminal area (Ai), and wall area percent (WA%) were also measured.
AWV% decreased as the Global Initiative for Chronic Obstructive Lung Disease (GOLD) spirometric grade increased (p < 0.0001). AWV% was lower in symptomatic (CAT score ≥ 10) subjects than in non-symptomatic subjects (p = 0.036). AWV% was more closely correlated with forced expiratory volume in 1 s (FEV) and ratio of residual volume to total lung capacity (RV/TLC) than Ai, Ai to lung volume ratio, and volume of either the lung or the airway tree. Multivariate analyses showed that lower AWV% was associated with lower FEV and higher RV/TLC, independent of LAV%, WA%, and TAC.
A disproportionally small airway tree with a relatively large lung could lead to airflow obstruction and gas trapping in COPD. AWV% is an easily measured CT biomarker that may elucidate the clinical impacts of the airway-lung interaction in COPD.
慢性阻塞性肺疾病（COPD）的主要结构变化是气道管腔尺寸减小和肺容积增加。然而，尽管气道的外壁与肺实质相连，并且实质的机械性能影响气道的行为，但对于气道和肺大小对肺功能和症状的相互作用知之甚少。本研究通过建立一种新的计算机断层扫描（CT）指标，即气道体积百分比（AWV%），来检查这些影响，该指标定义为气道树与肺容积的百分比比值。
对 147 名稳定的男性 COPD 患者进行吸气性胸部 CT、肺功能和 COPD 评估测试（CAT）分析。自动分割整个气道树，并计算右肺上、中、下叶气道树体积与右肺体积的百分比比值作为右肺的 AWV%。还测量了低衰减体积百分比（LAV%）、总气道计数（TAC）、气道内腔面积（Ai）和壁面积百分比（WA%）。
AWV%随着全球倡议慢性阻塞性肺疾病（GOLD）肺功能分级的增加而降低（p<0.0001）。在有症状（CAT 评分≥10）的患者中，AWV%低于无症状患者（p=0.036）。AWV%与用力呼气量 1 秒（FEV）和残气量与肺总量的比值（RV/TLC）的相关性较 Ai、Ai 与肺容积的比值以及肺或气道树的容积更密切。多变量分析表明，较低的 AWV%与较低的 FEV 和较高的 RV/TLC 相关，独立于 LAV%、WA%和 TAC。
相对较大的肺伴有不成比例小的气道树可能导致 COPD 中的气流阻塞和气体潴留。AWV%是一种易于测量的 CT 生物标志物，可能阐明 COPD 中气道-肺相互作用的临床影响。
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