RespiratoryTier 2Topic

Effects of inflammation of the airways and associated diseases

Remodelling

Chronic airway inflammation drives structural "remodelling" - a distinct, partially irreversible process from the acute inflammatory/bronchoconstrictive component of asthma/COPD
Remodelling explains why long-standing asthma can develop a component of fixed airflow obstruction, not fully reversible with bronchodilators, unlike early/mild disease

Mechanism

Chronic inflammation (eosinophilic in typical asthma, neutrophilic in COPD/severe asthma) -> epithelial injury and repair cycles -> subepithelial fibrosis, smooth muscle hypertrophy/hyperplasia, mucous gland hyperplasia, angiogenesis
Result: thickened airway wall, reduced luminal calibre independent of bronchoconstriction, and an irreversible component to airflow limitation

Testing

Spirometry showing incomplete reversibility with bronchodilator/steroid trial in a patient with a long asthma history suggests remodelling has occurred
Distinguished from COPD by history/pattern, but can coexist (asthma-COPD overlap)

Management

Earlier, more aggressive control of inflammation (inhaled corticosteroids) is thought to reduce the degree of remodelling over time - a rationale for early anti-inflammatory treatment in asthma rather than reliever-only management

Associations

Asthma, COPD, asthma-COPD overlap, fixed airflow obstruction

Key point

Remodelling is a key reason why "outgrowing" asthma is less complete in patients with a history of poorly controlled disease - a rationale for treating to prevent, not just relieve, inflammation

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