Asthma is a common inflammatory disease of the airways associated with episodes of reversible over-reactivity of the airway smooth muscle. The mucous membranes and muscle layers of the bronchi become thickened and the mucous glands enlarge,reducing airflow in the lower respiratory tract. The walls swell and thicken with inflammatory exudate and an influx of inflammatory cells,especially eosinophils. During an asthmatic attack,spasmodic contraction of bronchial muscle constricts the airway and there is excessive secretion of thick sticky mucus,which further narrows the airway. Inspiration is normal but only partial expiration is achieved,so lungs become hyperinflated and there is severe dyspnoea and wheezing.
Non-specific factors that may precipitate asthma attacks include:
- Cold air.
- Cigarette smoking.
- Air pollution.
- Upper respiratory tract infection
- Emotional stress.
There are two clinical categories of asthma,which generally gives rise to identical symptoms and are treated in the same way. Important differences include typical age of onset and the contribution of an element of allergy. Asthma,whatever the aetiology,can usually be well controlled with inhaled anti-inflammatory and bronchodilator agents,enabling people to live a normal life.
- 1)atopic( childhood onset,extrinsic) asthma.
2) Non-atopic( adult onset,intrinsic) asthma.
