Bronchiolitis

Cunningham, Steve

Acute viral bronchiolitis is a common viral lower respiratory tract infection in young children. Most typically caused by respiratory syncytial virus in 70% of cases, the condition lasts for 4 to 7 days, with a prolonged cough in many. Children with comorbidity, particularly those born prematurely or with significant congenital heart disease, are at risk of more severe disease. Nasal obstruction progresses over 3 to 4 days to difficulty with feeding and increased work of breathing with hypoxemia. Crackles and/or wheeze may be auscultated. Apnoea may be a presenting sign in those less than 3 months of age. Viral load is highest at peak of symptoms and in those with more severe disease. Approximately 2% to 3% of all children are admitted to hospital with bronchiolitis. The differential diagnosis may include bacterial pneumonia, congenital lesions of the lung or heart, or an interstitial lung disease. There are no effective treatments, and admission is for feeding support (by nasogastric or intravenous fluids) or treatment of hypoxemia. Critical care support is required for some infants experiencing respiratory failure, though mortality rates remain unchanged. Practice within and between countries varies significantly and alignment of practice is a common goal of guidelines. Vaccines for RSV are in advanced development, as are several antiviral therapies for RSV. In most children, acute symptoms improve within 5 to 7 days and cough by 2 weeks. Recurrent wheeze is common following acute bronchiolitis and a good association with a diagnosis of asthma in childhood.