Asthma is described in the book of guidelines for the diagnosis and management of asthma as follows:
- Asthma is a lung disease with periodic symptoms, nocturnal attacks, seasonal variations and symptoms produced by allergen exposure and exertion.
Asthma is defined by the following characteristics:
1) airway obstruction which is reversible (but not completely in some individuals), either spontaneously or by treatment;
2) inflammation of the airway mucosa by the infiltration of eosinophils, mast cells and T-lymphocytes; and 3) increased airway responsiveness to a variety of stimuli (National Asthma Education Programme Expert Panel Report).
The common factor in asthma is the abnormal hyperreactivity of the airways, which respond to a variety of stimuli. The production of mucus and the contraction of the bronchial smooth muscles causes constriction of the airways, and prevents the normal passive process of expiration. The continued process may produce chronic airway obstruction.
- Pathophysiology:
The development of airway obstruction is responsible for the clinical manifestation of asthma. Allergy has a significant role in the pathophysiology of asthma. Allergic inflammation in the lungs is enhanced by exposure to allergens by direct activation of T-lymphocytes, and release of inflammatory mediators, epithelial disruption and mucosal oedema. Airway inflammation is believed to be the primary mechanism responsible for airway hyperresponsiveness in asthma.
Asthmatic individuals develop clinical symptoms such as chronic cough, wheezing and dyspnea after exposure to allergens, environmental irritants, viral infections, cold air or exercise.
Management of asthma can be summarized as diagnosis and avoidance of the trigger, control of inflammation in the lungs by proper anti-inflammatory treatment, frequent monitoring of the degree of inflammation, and control of the symptoms.