Relationship between lung function and quantitative computed tomographic parameters of airway remodeling, air trapping, and emphysema in patients with asthma and chronic obstructive pulmonary disease: A single-center study

• Published in: Journal of allergy and clinical immunology Vol. 137; no. 5; pp. 1413 - 1422.e12
• Main Authors: Hartley, Ruth A., Barker, Bethan L., Newby, Chris, Pakkal, Mini, Baldi, Simonetta, Kajekar, Radhika, Kay, Richard, Laurencin, Marie, Marshall, Richard P., Sousa, Ana R., Parmar, Harsukh, Siddiqui, Salman, Gupta, Sumit, Brightling, Chris E.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.05.2016; Elsevier Limited; Mosby
• Subjects: Adult; Aged; Airway Remodeling; Allergy and Immunology; Asthma; Asthma - diagnostic imaging; Asthma - pathology; Asthma - physiopathology; Asthma and Lower Airway Disease; asthma-COPD overlap syndrome; Chronic illnesses; Chronic obstructive pulmonary disease; emphysema; Female; Forced Expiratory Volume; gas trapping; Health risk assessment; Humans; Male; Middle Aged; Patients; Pulmonary Disease, Chronic Obstructive - diagnostic imaging; Pulmonary Disease, Chronic Obstructive - pathology; Pulmonary Disease, Chronic Obstructive - physiopathology; Pulmonary Emphysema - diagnostic imaging; Pulmonary Emphysema - pathology; Pulmonary Emphysema - physiopathology; quantitative computed tomography; small airway disease; Tomography, X-Ray Computed; Perc15; QCT; gas trapping; airway remodeling; ICC; WA; TA; MLDE/I; Asthma; emphysema; BSA; CT; small airway disease; GINA; LA; KCO; quantitative computed tomography; asthma-COPD overlap syndrome; chronic obstructive pulmonary disease; COPD; Intraclass correlation; Hounsfield units below which 15% of the voxels lie; Total area; Computed tomography; MLD E/I; Mean lung density expiratory/inspiratory ratio; Body surface area; Transfer coefficient; Lumen area; Wall area; Global Initiative for Asthma
• ISSN: 0091-6749; 1085-8725; 1097-6825; 1097-6825
• DOI: 10.1016/j.jaci.2016.02.001

There is a paucity of studies comparing asthma and chronic obstructive pulmonary disease (COPD) based on thoracic quantitative computed tomographic (QCT) parameters. We sought to compare QCT parameters of airway remodeling, air trapping, and emphysema between asthmatic patients and patients with COPD and explore their relationship with airflow limitation. Asthmatic patients (n = 171), patients with COPD (n = 81), and healthy subjects (n = 49) recruited from a single center underwent QCT and clinical characterization. Proximal airway percentage wall area (%WA) was significantly increased in asthmatic patients (62.5% [SD, 2.2]) and patients with COPD (62.7% [SD, 2.3]) compared with that in healthy control subjects (60.3% [SD, 2.2], P < .001). Air trapping measured based on mean lung density expiratory/inspiratory ratio was significantly increased in patients with COPD (mean, 0.922 [SD, 0.037]) and asthmatic patients (mean, 0.852 [SD, 0.061]) compared with that in healthy subjects (mean, 0.816 [SD, 0.066], P < .001). Emphysema assessed based on lung density measured by using Hounsfield units below which 15% of the voxels lie (Perc15) was a feature of COPD only (patients with COPD: mean, −964 [SD, 19.62] vs asthmatic patients: mean, −937 [SD, 22.7] and healthy subjects: mean, −937 [SD, 17.1], P < .001). Multiple regression analyses showed that the strongest predictor of lung function impairment in asthmatic patients was %WA, whereas in the COPD and asthma subgrouped with postbronchodilator FEV1 percent predicted value of less than 80%, it was air trapping. Factor analysis of QCT parameters in asthmatic patients and patients with COPD combined determined 3 components, with %WA, air trapping, and Perc15 values being the highest loading factors. Cluster analysis identified 3 clusters with mild, moderate, or severe lung function impairment with corresponding decreased lung density (Perc15 values) and increased air trapping. In asthmatic patients and patients with COPD, lung function impairment is strongly associated with air trapping, with a contribution from proximal airway narrowing in asthmatic patients.