Choi Sanghun, Hoffman Eric A, Wenzel Sally E, Castro Mario, Fain Sean B, Jarjour Nizar N, Schiebler Mark L, Chen Kun, Lin Ching-Long
Department of Mechanical and Industrial Engineering, University of Iowa, Iowa City, Iowa; IIHR-Hydroscience and Engineering, University of Iowa, Iowa City, Iowa;
Department of Biomedical Engineering, University of Iowa, Iowa City, Iowa; Department of Radiology, University of Iowa, Iowa City, Iowa; Department of Internal Medicine, University of Iowa, Iowa City, Iowa;
J Appl Physiol (1985). 2015 May 15;118(10):1286-98. doi: 10.1152/japplphysiol.01094.2014. Epub 2015 Mar 26.
Relationships between structural and functional variables in asthmatic lungs at local and global (or lobar) levels remain to be discovered. This study aims to investigate local alterations of structural variables [bifurcation angle, circularity, airway wall thickness (WT), and hydraulic diameter (Dh)] in asthmatic subjects, and their correlations with other imaging and pulmonary function test-based global and lobar metrics, including lung shape, air-trapping, regional volume change, and more. Sixty-one healthy subjects, and 67 nonsevere and 67 severe asthmatic subjects were studied. The structural variables were derived from computed tomography images at total lung capacity (TLC). Air-trapping was measured at functional residual capacity, and regional volume change (derived from image registration) was measured between functional residual capacity and TLC. The tracheal diameter and WT predicted by 61 healthy subjects were used to normalize the Dh and WT. New normalization schemes allowed for the dissociation of luminal narrowing and wall thickening effects. In severe asthmatic subjects, the alteration of bifurcation angle was found to be correlated with a global lung shape at TLC, and circularity was significantly decreased in the right main bronchus. While normalized WT increased especially in the upper lobes of severe asthmatic subjects, normalized Dh decreased in the lower lobes. Among local structural variables, normalized Dh was the most representative variable, because it was significantly correlated with alterations of functional variables, including pulmonary function test's data. In conclusion, understanding multiscale phenomena may help to provide guidance in the search for potential imaging-based phenotypes for the development and outcomes assessment of therapeutic intervention.
哮喘肺脏局部和整体（或肺叶）水平的结构与功能变量之间的关系仍有待探索。本研究旨在调查哮喘患者结构变量[分叉角度、圆形度、气道壁厚度（WT）和水力直径（Dh）]的局部改变，以及它们与其他基于成像和肺功能测试的整体和肺叶指标的相关性，包括肺形状、气体潴留、区域体积变化等。研究了61名健康受试者、67名非重度哮喘患者和67名重度哮喘患者。结构变量来自全肺容量（TLC）时的计算机断层扫描图像。在功能残气量时测量气体潴留，在功能残气量和TLC之间测量区域体积变化（通过图像配准得出）。用61名健康受试者预测的气管直径和WT对Dh和WT进行标准化。新的标准化方案能够区分管腔狭窄和管壁增厚的影响。在重度哮喘患者中，发现分叉角度的改变与TLC时的整体肺形状相关，右主支气管的圆形度显著降低。虽然标准化WT在重度哮喘患者的上叶尤其增加，但标准化Dh在下叶降低。在局部结构变量中，标准化Dh是最具代表性的变量，因为它与功能变量的改变显著相关，包括肺功能测试数据。总之，理解多尺度现象可能有助于为寻找基于成像的潜在表型以用于治疗干预的开发和结果评估提供指导。
