BPD: old and new problems.

Bronchopulmonary dysplasia (BPD) is still one of the main long term complication of preterm birth, and it is the most common chronic respiratory disease in infants. Due to advances in perinatal care and neonatal respiratory therapy the clinical characteristics and the natural history of infants affected by BPD have widely changed in the last decades. The sever presentation of the old form of BPD has been replaced by a milder clinical form, without or with mild respiratory distress syndrome in the first days of life, that responds rapidly to surfactant therapy and instead requires prolonged ventilator support because of poor respiratory effort. "Old" and "new" BPD, are also histologically different, being two morphologic outcomes of variable combinations of factors injuring lungs of differing maturity. New BPD is characterized by diffusely reduced alveolar development, with airway injury, inflammation and fibrosis that are usually milder than in old form. Such "new" form of BPD is interpreted as a developmental disorder. The development of BPD is a multifactorial process with pathogenesis being linked to immature lung tissue, barotrauma and volutrauma resulting from mechanical ventilation, oxidant injury, and proinflammatory mediators.and inflammatory regulation may also have a role in the development of the new form. There is growing evidence that BPD results from an imbalance between proinflammatory and anti-inflammatory mechanisms, with a persistent imbalance that favors proinflammatory mechanisms. Reduction of the incidence and severity of BPD may be possible through a reduction of the amount of injury induced by respiratory support interventions.