Abstract
Fraction of exhaled nitric oxide (FeNO) provides information about chronic inflammation in asthma. However, its relationship with structural changes in the airways is unknown. We aimed to evaluate the correlation between computer-based airway changes and FeNO in patients with asthma. The wall area (WA) and airway inner luminal area (Ai) of the third- to sixth-generation bronchi were measured using three-dimensional computed tomography in asthmatic patients. Each value was corrected by body surface area (BSA). Relationships between FeNO and WA/BSA and Ai/BSA were evaluated. Forty-one clinically stable patients with asthma were evaluated. FeNO was significantly correlated with WA/BSA of the third-, fourth-, fifth- and sixth-generation bronchi (Spearman correlation coefficient (ρ) = 0.326, p = 0.041; ρ = 0.356, p = 0.025; ρ = 0.496, p = 0.002; and ρ = 0.529, p < 0.001, respectively). The correlation with sixth-generation bronchi was significantly greater than with the third-generation bronchi (p = 0.047). Partial rank correlation analysis indicated FeNO was significantly correlated with WA/BSA of the sixth-generation bronchi, independent from confounding factors of Ai/BSA, age, duration of asthma, dose of inhaled corticosteroid, blood eosinophil percentage, and blood IgE (ρ = 0.360, p = 0.034). In contrast, there was no correlation between FeNO and Ai/BSA. FeNO correlates with bronchial wall thickening in asthma patients. Measurement of FeNO may be useful to detect airway remodeling in asthma.
Highlights
Asthma is an airway inflammatory disease characterized by airway narrowing and wall thickening[1]
fraction of exhaled nitric oxide (FeNO) was correlated with the thickness of wall area throughout the third- to sixth-generation bronchi in asthma patients, and the correlation was strongest in the area of the sixth-generation bronchi
Partial rank correlation analysis demonstrated a significant correlation between FeNO level and the wall area of sixth-generation bronchi, independent of clinical factors that might affect FeNO expression and/or morphological airway changes
Summary
Asthma is an airway inflammatory disease characterized by airway narrowing and wall thickening[1]. Spirometry and peak expiratory flow measurements are widely used for the diagnosis and management of asthma[1] These physiological function tests evaluate the severity of airflow limitation caused by airway narrowing, but cannot directly evaluate bronchial wall thickening, which is an important pathogenic feature in asthma[2, 3]. Bronchial wall thickening in airway remodeling is attributed to the infiltration of inflammatory cells, thickening of the basement membrane, epithelial hyperplasia, and smooth muscle hypertrophy[4,5,6,7] These findings are mainly based on postmortem studies because of the difficulty in sampling bronchial tissues in clinical practice. Some previous studies using transbronchial biopsy reported similar pathologic changes in the airways of asthmatic patients, which correlated with bronchial hyperresponsiveness and disease severity[8,9,10,11]. How and whether structural changes in the airways in asthma correlate with FeNO is unknown
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