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A Novel Air Trapping Segment Score Identifies Opposing Effects of Obesity and Eosinophilia on Air Trapping in Asthma
Journal article   Open access   Peer reviewed

A Novel Air Trapping Segment Score Identifies Opposing Effects of Obesity and Eosinophilia on Air Trapping in Asthma

Clarus Leung, Monica Tang, Brendan K Huang, Sean B Fain, Eric A Hoffman, Jiwoong Choi, Eleanor M Dunican, David T Mauger, Loren C Denlinger, Nizar N Jarjour, …
American journal of respiratory and critical care medicine, Vol.209(10), pp.1196-1207
05/2024
DOI: 10.1164/rccm.202305-0802OC
PMCID: PMC11146546
PMID: 38113166
url
https://doi.org/10.1164/rccm.202305-0802OCView
Published (Version of record) Open Access

Abstract

Density thresholds in computed tomography (CT) lung scans quantify air trapping (AT) at the whole lung level but are not informative for AT in specific bronchopulmonary segments. To apply a segment-based measure of AT in asthma to investigate the clinical determinants of AT in asthma. In each of 19 bronchopulmonary segments in CT lung scans from 199 asthma patients, AT was categorized as present if lung attenuation was < -856 Hounsfield units at expiration in ≥ 15% of lung area. The resulting AT segment score (0-19) was related to patient outcomes. AT varied at the lung segment level and tended to persist at the patient and lung segment level over 3 years. Patients with widespread AT (>10 segments) had more severe asthma (p<0.05). The mean (± SD) AT segment score in patients with a BMI > 30 was lower than in patients with a BMI < 30 (3.5 ± 4.6 vs. 5.5 ± 6.3, p=0.008), and the frequency of AT in lower lobe segments in obese patients was less than in upper and middle lobe segments (35 vs. 46%, p=0.001). The AT segment score in patients with sputum eosinophil % > 2 was higher than in patients without sputum eosinophilia (7.0 ± 6.1 vs. 3.3 ± 4.9, p<0.0001). Lung segments with AT more frequently had airway mucus plugging than lung segments without AT (48 vs. 18%, p≤0.0001). In patients with asthma, air trapping is more severe in those with airway eosinophilia and mucus plugging whereas those who are obese have less severe trapping because their lower lobe segments are spared.
Asthma Computed Tomography Obesity Air trapping Eosinophil

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