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 with the majority being aged between three and six months. It presents with coughing, wheezing and shortness of breath which can cause some children difficulty in feeding. This inflammation is usually caused by respiratory syncytial virus (70% of cases) and is much more common in the winter months. Treatment is typically supportive and may involve the use of nebulized epinephrine or hypertonic saline. Bronchiolitis is common with up to one third of children being affected in their first year of life.

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. Crackles and/or wheeze are typical findings on listening to the chest with a stethoscope. 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.

Some signs of severe disease include:
 * poor feeding (less than half of usual fluid intake in preceding 24 hours)
 * lethargy
 * history of apnea
 * respiratory rate >70/min
 * presence of nasal flaring and/or grunting
 * severe chest wall recession
 * cyanosis

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.

Studies have shown there is a link between voluntary caesarean birth and an increased prevalence of bronchiolitis. A recent study by Perth's Telethon Institute for Child Health Research has shown an 11% increase in hospital admissions for children delivered this way. Children born prematurely (less than 35 weeks), with a low birth weight or who suffer from congenital heart disease may have higher rates of Bronchiolitis and are more likely to require hospital admission. There is evidence that breastfeeding provides some protection against bronchiolitis.

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. 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") people together in hospital wards 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).

Infant with bronchiolitis between the age of two and three months have a second infection by bacteria (usually a urinary tract infection) less than 6% of the time.

Prevention
Prevention of bronchiolitis relies strongly 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). In addition to good hygiene an improved immune system is a great tool for prevention. One way to improve the immune system is to feed the infant with breast milk, especially during the first month of life. Immunizations are available for premature infants who meet certain criteria (some cardiac and respiratory disorders) such as Palivizumab (a monoclonal antibody against RSV). Passive immunization therapy requires monthly injections every winter.

Management
Treatment and management of bronchiolitis is usually focused on the symptoms instead of the infection itself since the infection will run its course and complications are typically from the symptoms themselves. Without active treatment half of cases will go away in 13 days and 90% in three weeks.

Inhaled epinephrine
Inhaled epinephrine has been shown to decrease length of hospital admissions and overall length of stay compared to placebo.

Inhaled salbutamol
Nebulized and inhaled salbutamol (levo(1)-salbutamol) has been shown to decrease hospitalization rates.

Inhaled hypertonic saline
Inhaled hypertonic saline (3%) appears to be effective in improving clinical outcomes and shortening the duration of hospital stay.

Other medications
Currently other medications do not yet have evidence to support their use.

Non-effective treatments
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.

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.