Pathophysiology

There are three components to the airway limitation in asthma:

• bronchoconstriction - contraction of bronchial smooth muscle. This is the acute phase of an asthma attack, and time of onset is in minutes
• mucosal oedema; and
• increased secretion of tenacious mucous are features of the late phase which is mediated by mast cells and macrophages. These release chemotactic factors which attract further immune system cells and compound the inflammatory reaction

In fatal cases of asthma autopsy may reveal various chronic pathological features in the bronchial wall:

• eosinophilic infiltration
• an increase in number of goblet cells
• viscid mucus due to inflammatory protein leak, containing eosinophils, plugging bronchi
• thickening of the epithelial basement membrane
• there may be hypertrophy of bronchial muscle

The lungs themselves may be overinflated but otherwise normal.

These features may be found to a minor degree in patients with apparently well-controlled asthma.