الفهرس 
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Abstract
Acute viral bronchiolitis is the most common lower respiratory tract condition and most common reason for admission to hospital in infants. It is a cause of substantial morbidity and health care costs in young infants.
Acute bronchiolitis is a far reaching illness. Virtually all children have been infected with RSV by the age of 2 years, and nearly half of those will experience two infections of those infected, 40% will develop a lower respiratory tract infection.
Bronchiolitis is an inflammation of the bronchioles and most cases are viral in origin. RSV is the most common underlying viral infection and has been isolated from 50% to 75% of children younger than 2 years of age hospitalized with bronchiolitis. Other important viral causes include adenovirus, influenza virus, parainfluenza virus, human metapneumovirus, and rhinovirus. Mycoplasma pneumoniaemay occasionally be associated with bronchiolitis.
Early symptoms of acute bronchiolitis include rhinitis (inflammation of nasal mucosa) and coughing, with the development of lower respiratory tract symptoms one or two days later.Some children have a low grade pyrexia early in the illness but this is frequently absent when the infant eventually presents at hospital.This prodromal stage is then followed by the onset of tachpnea, difficulty with breathing, chest retractions and audible expiratory wheezing with rhonchi and/or crackles heard on auscultation. Agitation and poor feeding as a result of nasal obstruction and hypoxia are common, and the cough may cause vomiting with the risk of aspiration.Preterm infants may present with an episode of apnea.
The diagnosis of acute viral bronchiolitis is based on theclinical findings, including the child’s symptoms, age and the presence of an RSV epidemic in the community. Thiscan easily be confirmed by the identification of the virusin nasopharyngeal aspirates using immunofluorescent antibody tests or enzyme-linked immunoabsorbant assays(ELISA). A negative test for RSV does not exclude the diagnosis. Any infant admitted with a diagnosis of RSVbronchiolitis should have oxygen saturation monitoringto detect hypoxaemia.
A chest X-ray (CXR) is not routinely indicated but should be considered if the diagnosis is in doubt or if there is a suspicion of secondary bacterial infection (deterioration in clinical condition; high, prolonged fever; neutrophilia; or evidence of septicaemia). In uncomplicated bronchiolitis, the CXR demonstrates hyperinflation, areas of peribronchial thickening, patchy atelectasis or consolidation, typically in the right upper lobe.
The white cell count may be normal or raised. Blood electrolyte estimation should be performed in severe cases where infants have been unable to feed because of severe respiratory distress. For the majority of infants, blood tests are not helpful.
The predominant pathological features in acute bronchiolitis are inflammation of the respiratory and terminal bronchioles, the process includes edema, necrosis of epithelial cells, production of mucus and possibly some degree of bronchospasm.
There is a high degree of practice variability with respect to therapeutic measures for bronchiolitis. Many therapies that have proven effective in other disease entities, such as asthma and cystic fibrosis, have been used, although it is important to recognize differences in pathophysiology that may lead to different clinical responses. Recent literature has focused on systematically analyzing the available data regarding common therapies to determine whether it supports their routine use. Overall, it seems that supportive care which is concentrating on the major effects of the condition, namelyinadequate feeding , respiratory distress and apneas, should be the cornerstone of management and that most pharmacologic measures offer limited, if any, benefit in the treatment of bronchiolitis.