[Persistent pulmonary hypertension of the newborn]

Persistent pulmonary hypertension of the newborn (PPHN) is a cardiopulmonary disorder characterized by systemic arterial hypoxemia secondary to elevated pulmonary vascular resistance with resultant shunting of pulmonary blood flow to the systemic circulation. This disorder can be classified into four forms dependent on the etiology of the pulmonary hypertension: (1) Hypoplastic lung associated with congenital diaphragmatic hernia and oligohydramnions. (2) Primary PPHN (without known causative factor), such as preterm PPHN. (3) Secondary PPHN (with known causative factor), such as meconium aspiration syndrome, birth asphyxia or respiratory distress syndrome. (4) Relative PPHN associated with heart failure of hydrops fetalis or ischemic myocardial dysfunction. Inhalation of nitric oxide, which previously known as endothelial-derived-relaxation-factor, has been studied intensively as therapy for PPHN.