A large number of studies has recently stressed the very high prevalence of viral respiratory infections in the first year of life as the main cause of lower airway disease. The majority of infants present with symptoms of acute respiratory infection, one third with lower airway infection and approximately one third of these with wheeze. Many studies detect rhinovirus as the most common cause of wheezing in infants, whereas only 10% has been associated with respiratory syncytial virus.
Clinically, we define acute viral bronchiolitis as a syndrome of expiratory wheezing, fine inspiratory crackles, retractions, severe tachypnoea. In pathophysiology, three variations are known: complete airway obstruction; incomplete airway obstruction and peribronchial alveolar infiltration. Air trapping is a main characteristic of true bronchiolitis with complete obstruction.
Diagnosis is mostly clinical, due to a difficult and expensive viral identification. The most frequent complications are atelectasis, respiratory failure, severe pneumonia, apnoea (very young or premature babies), prolonged or recurrent wheezing episodes after the acute phase of bronchiolitis. In the literature, the risk factors for severe bronchiolitis are well known: age less than 4 months, prematurity, immunodeficiencies, chronic lung or heart disease.
Treatment of acute bronchiolitis depends on the severity of illness, hypoxia or very young age of infant.
In mild cases we suggest no special medications, only supportive measures. In moderate and severe cases, hospital admission is a frequent option. Medical treatment includes: oxygen, systemic corticosteroids (controversial in the literature), fluids, decongestants (therapy for upper airway obstruction of utmost value).