A chronic inflammatory disease of the airways which leads to muscle spasm, mucus plugging, and oedema. It results
in recurrent wheezing, cough, breathlessness, and chest tightness.

Acute attacks may be precipitated by upper respiratory tract infections (e.g. flu) and exposure to irritant substances (e.g. dust, exercise, and cold).


  • Not known but associated with allergies, inherited and environmental factors

Clinical features

  • No fever (if fever present, refer to pneumonia)
  • Difficulty in breathing (usually recurrent attacks) with chest tightness, with or without use of accessory muscles.  Patients may not appear very distressed despite a severe attack
  • Wheezing, rhonchi
  • Cough – usually dry, may be intermittent, persistent, or acute, especially at night
  • Severe forms: failure to complete sentences, darkening of lips, oral mucosa and extremities (cyanosis)

Differential diagnosis

  • Heart failure
  • Other causes of chronic cough
  • Bronchiolitis
  • Bronchiectasis


  • Diagnosis is mainly by clinical features

Specialised investigations

  • Peak flow rate: the peak flow rate increases to about 200 ml
    following administration of a bronchodilator
  • Spirometry (an increase in Forced Expiratory Volume
    (FEV) of >12% after bronchodilation)
  • Sputum: for eosinophilia

If evidence of bacterial infection

  • Chest X-ray
  • Blood: complete blood count

General principles of management

  • Inhalation route is always preferred as it delivers the medicines directly to the airways; the dose required is
    smaller, the side-effects are reduced

    • E.g. nebuliser solutions for acute severe asthma are given over 5-10 minutes, usually driven by oxygen in hospital
    • In children having acute attacks, use spacers to administer inhaler puffs
  • Oral route may be used if inhalation is not possible but systemic side-effects occur more frequently, onset of
    action is slower and dose required is higher
  • Parenteral route is used only in very severe cases when nebulisation is not adequate