Chronic inflammatory disorder of episodic difficulty in breathing due to a hyperactivity of the lungs in response to one or more stimuli.
Affects up to 20% of population.
Due to overreaction of linings of the trachea and bronchi to a stimulus.
Triggers – allergens (eg pollens, dust mite, bacteria); cold dry air; exercise (EIA – exercise induced asthma); psychological (eg stress, anxiety); infections (eg respiratory tract infection); drugs (eg aspirin, beta-adrenoreceptor antagonists); chemicals (eg isocyanates)
3 factors narrow airways:
1) Mucosal swelling and inflammation (from mast cell and basophil degranulation release of prostaglandins, histamine and other inflammatory mediators)
2) Increased mucous formation
3) Bronchial muscle contraction
Initially presents in a number of ways – varies from a persistent cough to recurrent episode of difficulty breathing (dyspnoea) – also associated with wheezing (high pitched noise from turbulent airflow through a narrowed airway).
Differential diagnosis – pulmonary oedema, COPD, airway obstruction, pneumothorax, pulmonary embolism, bronchiectasis
Prognosis – most childhood cases are grown out of in adolescence
Undertreatment and inappropriate therapy are considered major contributors to asthma morbidity and mortality .
Behaviour – stop smoking; avoid allergens; patient education
Avoid beta-blockers and NSAID’s (can make asthma worse)