Bronchiolitis

Bronchiolitis is inflammation of the bronchioles, the smallest air passages of the lungs. It usually occurs in children less than two years of age and presents with coughing, wheezing, and shortness of breath. This inflammation is usually caused by viruses. Treatment is typically supportive but may involve the use of nebulized epinephrine or hypertonic saline.

Signs and symptoms
In a typical case, an infant under two years of age develops cough, wheeze, and shortness of breath over one or two days. 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.

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

Diagnosis
The diagnosis is typically made by clinical examination. Chest X-ray is sometimes useful to exclude pneumonia, but not indicated in routine cases.

Testing for the specific viral cause can be done but has little effect on management and thus is not routinely recommended. In a systematic review, RSV testing by direct immunofluorescence testing on nasopharyngeal aspirate had a sensitivity of 61% and specificity of 89%. Identification of those who are RSV-positive can help 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).

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.

Rarely, bronchiolitis obliterans occurs, that is, when bronchitis presents with concomitant non-reversible obstruction due to the bronchioles (small airway branches) becoming compressed and narrowed by fibrosis (scar tissue) and/or inflammation. This form of bronchiolitis is life-threatening and has various causes.

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 major 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

Management
Therapy for bronchiolitis is primarily supportive. Nebulized epinephrine may decrease the need for hospitalization while nebulized hypertonic saline appears to be effective in improving clinical outcomes and shortening the duration of hospital stay. All other medications do not have evidence to support there use.

Non effective
Ribavirin is an antiviral drug which does not appear to be effective for bronchiolitis. 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. DNAse has not been found to be effective.

Complications
Middle ear bacterial infection

Development of asthma later (bronchial hyperactivity)

Epidemiology
90% of the patients are aged between 1 and 9 months old. Bronchiolitis is the most common cause of hospitalization up to the first year of life. It is epidemic in winters.