Acute lower respiratory tract infection (LRTI) is common in children and in up to 15% of hospitalized cases subsequent referral to a paediatric intensive care unit is necessary. Respiratory syncytial virus, parainfluenza viruses, rhinoviruses and newly emerging viruses like human metapneumovirus, human bocavirus and coronaviruses are commonly isolated pathogens from these patients. Developmental aspects of respiratory anatomy and mechanics are of great importance in the pathophysiology of LRTI and explain why children with the condition are more susceptible to respiratory insufficiency compared to adults. Studies on histopathological changes in viral LRTI have identified both direct viral induced cellular damage and immunopathology as playing roles in the development of severe respiratory distress. Molecular diagnostic tools, most importantly real time polymerase chain reaction, have shown that mixed viral infections are common. Clinical relevance is, however, uncertain. Host factors like age, co-morbidity and possibly genetic factors are probably more important in modulating disease severity. Treatment is limited to supportive measures. Consensus regarding the optimal mode of invasive ventilatory support is lacking. A shift from invasive ventilatory support to non-invasive ventilation is occurring. Ribavirin, corticosteroids, immunoglobulines and bronchodilators are ineffective in treating viral LRTI. Antibiotics are prescribed commonly, but their effect has not been demonstrated in prospective randomised trials and a bacterial pathogen is only found in half the cases. Surfactant and small interfering RNAs may be promising treatment options in the future. Prospective studies however are needed to demonstrate their effect.
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