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Bronchiolitis, a viral infection which predominantly affects children under 2 years of age, is due to respiratory syncythial virus (RSV) and several other bacteria and viruses. An inflammatory oedema of the bronchial mucous obstructs the smaller airways, which in turn may cause severe air-trapping, atelectasis and bronchopneumonia. The alveolar-capillary membrane, directly damaged by the infection but also by hypoxic pulmonary vasoconstriction and hypoperfusion, can involve type II pneumocytes or inactivate surfactant, which favours bronchiolar and alveolar collapse and lung permeability to macromolecules. Severe forms, requiring artificial ventilation, can lead to death of patient from hypoxic origin but also from sudden cardio-circulatory failure due to reduction of cardiac output consequent to thorax over-inflation.
Exogenous surfactant has been tested in order to restore the surfactant system, so that, if artificial ventilation with PEEP recruits alveoli, surfactant may stabilise them, maintain their patency and thus restore ventilation of non-ventilated areas.
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