Bronchiolitis

Bronchiolitis is inflammation of the bronchioles, the smallest air passages of the lungs.

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Causes

The term usually refers to acute viral bronchiolitis, a common disease in infancy. This is most commonly caused by respiratory syncytial virus (RSV, also known as human pneumovirus). (J21.0)

Other viruses which may cause this illness include metapneumovirus, influenza, parainfluenza, coronavirus, adenovirus, and rhinovirus.

The American Academy of Pediatrics has published a clinical practice guideline for the Diagnosis and Management of Bronchiolitis, including a review of the evidence and recommendations.

Presentation

In a typical case, an infant under two years of age develops cough, wheeze, and shortness of breath over one or two days. The diagnosis is made by clinical examination. Chest X-ray is sometimes useful to exclude pneumonia, but not indicated in routine cases.

Testing for specific viral cause (e.g. RSV by nasopharyngeal aspirate) is common, but has little effect on management. Identification of RSV-positive patients can be helpful for:

• disease surveillance
• grouping ("cohorting") patients together in hospital wards as to prevent cross infection
• predicting whether the disease course has peaked yet
• reducing the need for other diagnostic procedures (by providing confidence that a cause has been identified).

The infant may be breathless for several days. After the acute illness, it is common for the airways to remain sensitive for several weeks, leading to recurrent cough and wheeze.

There is a possible link with later asthma: possible explanations are that bronchiolitis causes asthma by inducing long term inflammation, or that children who are destined to be asthmatic are more susceptible to develop bronchiolitis.

Treatment

There is no effective specific treatment for bronchiolitis. Therapy is principally supportive. Frequent small feeds are encouraged to maintain hydration as evidenced by good urine output, and sometimes oxygen may be required to maintain blood oxygen levels. Suction of the nasopharynx is often performed to maintain a clear airway. In severe cases the infant may need to be fed via a nasogastric tube or it may even need intravenous fluids. In extreme cases, mechanical ventilation (for example, using CPAP) might be necessary.

Bronchodilator drugs such as salbutamol/albuterol or ipratropium are no longer recommended, but many clinicians offer a trial dose to see if there is any benefit (especially if there is a family history of asthma, since it can be difficult to clinically distinguish bronchiolitis from a viral-induced asthma). Racemic epinephrine is another drug that is sometimes given.

Ribavirin is an antiviral drug which has a controversial role in treating RSV infection. There is no proven benefit but it is used sometimes for infants with pre-existing lung, heart or immune disease. Antibiotics are often given in case of a bacterial infection complicating bronchiolitis, but have no effect on the underlying viral infection.

Corticosteroids have no proven benefit in bronchiolitis treatment and are not advised.

There is some interest in the use of hypertonic saline in bronchiolitis. Initially recommended for use in cystic fibrosis patients, it is speculated to increase hydration of secretions, thus facilitating their removal.

Prevention

In general, prevention of bronchiolitis relies on measures to reduce the spread of the viruses that cause respiratory infections (that is, handwashing, and avoiding exposure to those symptomatic with respiratory infections).

Premature infants, and others with certain majory cardiac and respiratory disorders, can receive passive immunization with Palivizumab (a monoclonal antibody against RSV). This form of passive immunization therapy requires monthly injections every winter. Whether it could benefit infants with lung problems secondary to muscular dystrophies and other vulnerable groups is currently unknown.

See also

• Respiratory syncytial virus