Definition of asthma

Asthma is a chronic inflammatory disorder of the airways in which many cells and cellular elements play a role, in particular, mast cells, eosinophils, T lymphocytes, macrophages, neutrophils, and epithelial cells. In susceptible individuals, this inflammation causes recurrent episodes of wheezing, breathlessness, chest tightness, and coughing, particularly at night or in the early morning. These episodes are usually associated with widespread but variable airflow obstruction that is often reversible either spontaneously or with treatment. The inflammation also causes an associated increase in the existing bronchial hyperresponsiveness to a variety of stimuli.¹⁰

Airflow obstruction (excessive airway narrowing) in asthma is the result of contraction of the airway smooth muscle and swelling of the airway wall due to:

• smooth muscle hypertrophy and hyperplasia
• inflammatory cell infiltration
• oedema
• goblet cell and mucous gland hyperplasia
• mucus hypersecretion
• protein deposition including collagen
• epithelial desquamation.

This inflammatory process can cause permanent changes in the airways. Long-term changes include increased smooth muscle, increase in bronchial blood vessels, thickening of collagen layers and loss of normal distensibility of the airway. 

Potential triggers for the inflammatory process in asthma include allergy, viral respiratory infections, gastro-oesophageal reflux (GORD), irritants such as tobacco smoke, air pollutants and occupational dusts, gases and chemicals, certain drugs, and non-specific stimuli such as cold air exposure and exercise.

Education of people with asthma about the nature of the disease - that it is more than bronchospasm, and is an inflammatory disease - helps them gain a greater understanding of the need for separate types of medication for asthma management:

• bronchodilator (also referred to as reliever) medication
• anti-inflammatory (also referred to as preventer) medication
• long-acting beta₂ agonist (also known as symptom controller) medication usually prescribed in combination with an inhaled corticosteroid (ICS) preventer. Combination medications consist of an ICS and a symptom controller in a single inhaler device.

In addition, education about other measures to improve asthma control is important:

• allergen avoidance/control
• use of a written asthma action plan
• smoking cessation, diet and exercise (including specific management of exercise-induced asthma if required).

Content Created (Thursday, 16 November 2006)