Epidemiology

• It is common throughout childhood, except in the immediate neonatal period, when it relatively rare.
• 18.9% of 10 year-old children were shown to be wheezing on the Isle of Wight with the average age of onset of 3 years.^[1]
• Other studies have reported a prevalence of wheeze, in preschool children, of between 25% and 38%.^[2]
• One study of preschool children found that the presence of both exercise-induced wheeze and a history of atopic disorders indicated a likelihood of 53.2% developing asthma.^[2]

Causes

• Respiratory tract infections.
• Transient wheezing in infancy.
• Asthma.
• Bronchiolitis.
• Croup.
• Cigarette smoke or other forms of air pollution.
• Gastro-oesophageal reflux.
• Foreign body inhalation.
• Rare causes include tracheo-oesophageal fistula, following bronchopulmonary dysplasia, bronchiectasis, heart failure, congenital heart disease, cystic fibrosis, immunodeficiency, extrinsic compression of airways (eg tumours, vascular rings), tracheobronchomalacia and ciliary dyskinesia.

Presentation and management

Always consider the presence of any red flags indicating the need for urgent assessment and treatment, eg poor feeding, cyanosis, respiratory distress, drowsiness or poor response to treatment. See also separate article Children with Respiratory Difficulties.

• There are two main forms of presentation depending upon onset and age:
  • Acute onset of wheezing in an infant.
  • Recurrent or persistent wheeze.
• Wheezing starting perinatally suggests structural abnormalities.
• Clubbing occurs in chronic lung infection, congenital heart disease and, rarely, in uncomplicated asthma.
• Allergic rhinitis, urticaria and eczema suggest asthma (or an allergic reaction in a child with eczema).
• Nasal polyps are found in allergic conditions or cystic fibrosis.

Transient wheezing in infancy

• Transient early wheezing defines recurrent wheezing in non-atopic infants or toddlers and tends to disappear by the age of 3 years.^[3]
• The most common cause for non-atopic wheezing is viral infection, especially by respiratory syncytial virus.^[3]
• Short-term management with inhaled bronchodilators is sufficient if required.^[3]
• Early sensitisation to indoor allergens, especially to pets, and atopic dermatitis predict subsequent development of asthma after wheezing in infancy.^[4]
• If hospital admission for wheezing occurs in infancy, more than a third of children will suffer from asthma at early school age. The risk is significantly increased with recurrent wheezing in infancy and the development of allergic manifestations (eg blood eosinophilia, atopic dermatitis, elevated total serum immunoglobulin E (IgE)).

Recurrent or persistent wheeze

• Caused by obstruction anywhere from intrathoracic trachea to large bronchioles.
• Wheezing persisting for, or recurring for, more than four weeks is most commonly caused by reactive airways disease (asthma).
• This diagnosis is also suggested by recurring cough and response to bronchodilator therapy.

Investigation of possible causes

• CXR: can demonstrate the presence of a foreign body, structural anomalies, an enlarged heart, masses, and pulmonary infiltrates.
• Sweat chloride test for cystic fibrosis.
• Allergy testing.
• Barium swallow for tracheo-oesophageal fistula and other anomalies.^[5]
• Spirometry in children aged over 6 years.

Further investigations may be needed for rarer causes, eg echocardiogram, MRI/CT scan of the chest.

Prognosis

The prognosis depends on the underlying cause.