Computed tomographic measures of airway morphology in smokers and never-smoking normals

• Published in: Journal of applied physiology (1985) Vol. 116; no. 6; pp. 668 - 673
• Main Authors: Washko, G R, Diaz, A A, Kim, V, Barr, R G, Dransfield, M T, Schroeder, J, Reilly, J J, Ramsdell, J W, McKenzie, A, Van Beek, E J R, Lynch, D A, Butler, J P, Han, M K
• Format: Journal Article
• Language: English
• Published: United States American Physiological Society 15.03.2014
• Subjects: Aged; Airway management; Airway Remodeling; Case-Control Studies; Chronic obstructive pulmonary disease; Female; Forced Expiratory Volume; Humans; Lung - diagnostic imaging; Lung - physiopathology; Lungs; Male; Middle Aged; Morphology; Predictive Value of Tests; Pulmonary Disease, Chronic Obstructive - diagnostic imaging; Pulmonary Disease, Chronic Obstructive - etiology; Pulmonary Disease, Chronic Obstructive - physiopathology; Severity of Illness Index; Smoking; Smoking - adverse effects; Spirometry; Tomography; Tomography, X-Ray Computed; Vital Capacity; computed tomographic scan; lumen; wall area; chronic obstructive pulmonary disease
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00004.2013

Bronchial wall area percent (WA% = 100 × wall area/total bronchial cross sectional area) is a standard computed tomographic (CT) measure of central airway morphology utilized in smokers with chronic obstructive pulmonary disease (COPD). Although it provides significant clinical correlations, the range of reported WA% is narrow. This suggests limited macroscopic change in response to smoking or that remodeling proportionally affects the airway wall and lumen dimensions such that their ratio is preserved. The objective of this study is to assess central airway wall area (WA), lumen area (Ai), and total bronchial area (Ao) from CT scans of 5,179 smokers and 92 never smoking normal subjects. In smokers, WA, Ai, and Ao were positively correlated with forced expiratory volume in 1 s (FEV1) expressed as a percent of predicted (FEV1%), and the WA% was negatively correlated with FEV1% (P < 0.0001 for all comparisons). Importantly, smokers with lower FEV1% tended to have airways of smaller cross-sectional area with lower WA. The increases in the WA% across GOLD stages of chronic obstructive pulmonary disease (COPD) can therefore not be due to increases in WA. The data suggest two possible origins for the WA% increases: 1) central airway remodeling resulting in overall reductions in airway caliber in excess of the decreased WA or 2) those with COPD had smaller native airways before they began smoking. In both cases, these observations provide an explanation for the limited range of values of WA% across stages of COPD.