BRONCHOPULMONARY DYSPLASIA (BPD)

DEF: Chronic lung disease characterized by persistent tachypnea, dyspnea, hypoxemia, and hypercarbia in neonates surviving hyaline membrane disease.
ETIOL: BPD occurs in neonates with a history of pulmonary immaturity and acute lung injury who have been treated with ventilatory support. The premature lung is believed to be particularly susceptible oxygen (O2) toxicity and iatrogenic barotrauma, resulting in persistent respiratory insufficiency. Whether infection (e.g., Ureaplasma), oxidant injury, or barotrauma is the primary insult, the inflammatory process likely exacerbates the prolonged lung damage characteristic of BPD.
CLIN: Most neonates with acute lung disease recover completely within the first week of life. The diagnosis of BPD is suspected when an affected neonate (typically premature) fails to recover as anticipated and instead may have a gradual increase in O2 and ventilatory requirements during the first month of life.
STUDIES: No specific tests exist to confirm the diagnosis of BPD. However, chest radiographic findings of strandlike densities in both lung fields alternating with areas of normal or increased lucency are consistent with BPD. Other disorders to rule out include cystic fibrosis (sweat chloride test), a1-antitrypsin deficiency (a1-antitrypsin levels), patent ductus arteriosus (PDA) (murmur, echocardiography), and viral pneumonia (viral cultures).
TX: Ideally, management of acute lung disease in premature infants should be aimed at preventing BPD by limiting exposure to mechanical ventilation and O2 therapy (if possible), judicious fluid administration, prompt management of PDA, and attention to optimal nutrition. Once diagnosed with BPD, neonates benefit from chronic administration of O2 with maintenance of PaO2 greater than 60 mm Hg or an O2 saturation greater than 90%; this chronic O2 therapy reduces the risk of developing pulmonary hypertension and cor pulmonale, severe complications of BPD. Additional O2 may be required during sleep and feedings. Congestive heart failure can frequently complicate the treatment of BPD. The development of pulmonary and systemic edema often requires chronic parenteral fluid restriction. Enteral fluid is better tolerated. Diuretics may be used with care; thiazide diuretics are preferred because they decrease urinary calcium excretion and may help prevent osteopenia of prematurity. Increased airway resistance and bronchial hyperreactivity may be treated with theophylline or b-adrenergic agents. Antiinflammatory therapy may also reduce O2 requirements and shorten the period of ventilator support. The tachypnea and heightened respiratory effort associated with BPD require that these infants receive increased caloric intake to achieve adequate growth. Caloric intake should be adjusted to enable a sustained weight gain of at least 10 g/kg/day. Infants with BPD have an increased susceptibility for developing severe pneumonia; therefore, respiratory infections should be prevented by avoiding exposure of the infant to patients, hospital personnel, and family members with respiratory symptoms. When viral respiratory infections occur in infants with BPD, O2, bronchodilator, and diuretic use are often increased for at least 1 week. If respiratory failure develops and ventilator therapy is required, mortality is high and recovery prolonged. In comparison with premature infants lacking BPD, survivors of BPD may have an increased incidence of neurodevelopmental abnormalities, visual and hearing deficits, and rehospitalization for respiratory illness in the first year of life. Because lung growth continues for the first few years of life, pulmonary function improves over that time, with most survivors achieving normal exercise tolerance by school age; evidence of increased airway reactivity can persist into adult life in a high percentage of patients.