Acute exacerbations of asthma in children can be triggered by exposure to allergens such as dust, pollution, animal hair or smoke, causing a type 1 (IgE-mediated) hypersensitivity reaction. This leads to bronchoconstriction and bronchial oedema.

Classification

Severe acute episode:

• Respiratory distress (use of accessory muscles of respiration, breathlessness resulting in inability to complete sentences, tachypnoea with a respiratory rate ≥ 25/min)
• Heart rate ≥ 110/min
• Peak expiratory flow rate 33-50% of predicted

Life threatening episode:

• Peak exploratory flow rate is <33% predicted
• Oxygen saturations <92%
• Silent chest on auscultation
• Weak or no respiratory effort
• Hypotension
• Exhaustion
• Confusion/altered conscious level

Differentials

Important differentials include:

• Pneumothorax
• Anaphylaxis
• Inhalation of a foreign body