Wheezing is a high-pitched, whistling sound that occurs when smaller airways are narrowed by presence of any of the following:
- Swelling of the mucosal lining.
- Excessive amounts of secretions.
- An inhaled foreign body.
- It is common throughout childhood, except in the immediate neonatal period, when it relatively rare. Approximately one in three children has at least one episode of wheeze before their third birthday.
- Studies have reported a prevalence of wheeze, in preschool children, of between 25% and 38%.
- 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.
- Respiratory tract infections.
- Transient wheezing in infancy.
- 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 Children with Respiratory Difficulties article.
No treatment has been shown to prevent progression of preschool wheeze to school-age asthma. Treatment is therefore only directed towards current symptoms. In all but the most severe cases, episodic symptoms should be treated with episodic treatment. If prophylactic treatment is initiated, it should be discontinued at the end of a strictly defined time period because many respiratory symptoms remit spontaneously in preschool children. Prednisolone is not indicated in preschool children with attacks of wheeze who are well enough to remain at home and is also not indicated for children admitted to hospital with episodic viral wheeze.
- 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.
- The most common cause for non-atopic wheezing is viral infection, especially by respiratory syncytial virus.
- Short-term management with inhaled bronchodilators is sufficient if required.
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.
- Spirometry in children aged over 6 years.
Further investigations may be needed for rarer causes - eg, echocardiogram, MRI/CT scan of the chest.
The prognosis depends on the underlying cause. Several cohort studies have shown that preschool children with wheeze have deficits in lung function at 6 years of age that persisted until early and middle adulthood, suggesting increased susceptibility in the first years of life that might lead to persistent sequelae.However, although almost 50% of children experience wheeze in the first six years of life, only 40% of them will report continued wheezing symptoms after childhood.
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