chapter  7
Asthma
ByFelix S. F. Ram, Elissa M. McDonald
Pages 27

Key characteristics that define asthma are bronchial hyper-responsiveness, reversible airway obstruction and inflammation. Early definitions of asthma included the presence of airways obstruction that could reverse spontaneously or with treatment, and also the increased narrowing of the airways to stimuli (e.g. histamine, cold air, exercise, viral upper respiratory infection, cigarette smoke or respiratory allergens) causing bronchial hyper-responsiveness. Management of asthma has been enhanced by the recognition that the airways sub-mucosa of patients with asthma are chronically inflamed with a typical inflammatory infiltrate, and that inflammatory processes are important in causing the main characteristics of asthma of airways obstruction and bronchial hyper-responsiveness. As a result of inflammation, the airways are hyper-responsive and they narrow easily in response to a wide range of stimuli. This may result in coughing, wheezing, chest tightness and shortness of breath, with symptoms often worse at night. Narrowing of the airways is usually reversible with appropriate pharmacological intervention, but in patients with chronic inflammatory conditions it leads to irreversible airflow obstruction (BTS, 2008; Cressy and DeBoisblanc, 1998; EPR-3, 2007; Foggs, 2008; Levy et al., 2009). Characteristic pathology of asthmatic airways displays lung hyperinflation, smooth muscle hypertrophy, mucosal edema, lamina thickening, epithelial cell sloughing, cilia disruption and mucus hyper-secretion. Its pathology is further characterized by the presence of increased numbers of eosinophils, neutrophils, lymphocytes and plasma cells in the bronchial tissues, bronchial secretions and mucus.