Airway Remodeling in Severe Asthma

Studies of the airways of patients who die from asthma demonstrate thickened airway walls due to increases in smooth muscle mass, infiltration with inflammatory cells, deposition of connective tissue, vascular changes, and mucous gland hyperplasia, a condition that is termed airway remodeling. Airway remodeling may be a feature of milder and even asymptomatic asthma. The remodeling of airways can result in the worsening of airway narrowing, airflow obstruction, and disease progression.

Airway remodeling in asthma patients has been studied in vivo by performing endobronchial biopsies, the samples from which can then be evaluated for structural and inflammatory changes. Multidetector CT (MDCT) scan studies have recently been used to evaluate the extent of airway wall thickening as a noninvasive, highly reproducible method for studying individual airways. Several studies- using MDCT scanning have demonstrated that the airway walls of asthmatic patients are thicker than those of healthy subjects, and that airway wall thickness (WT) is related to the severity of disease and airflow obstruction. This thickening may be partially reversible with inhaled corticosteroid treatment in steroid-naive patients and may increase in the absence of inhaled corticosteroid treatment. The airway lumen area of stable patients with asthma is not narrowed compared with that of healthy control subjects and may even be dilated in those with more severe disease. These studies are often limited by the number of airways studied, small subject numbers, or the use of semi-quantitative techniques, Thus, the purpose of our study was to apply an automated airway analysis software comparing airway wall measurements among patients with severe and mild-to-moderate asthma and healthy subjects, and to correlate this with remodeling measurements of biopsy specimens from matched airway segments.

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Severe Asthma