Congenital Pulmonary Hypoplasia

A congenital or acquired syndrome with underdevelopment of one or both lungs.

Congenital pulmonary hypoplasia (CPH) is considered autosomal recessive inherited. However, it more often may be secondary to other intrauterine anomalies.

The hypoplastic lung has all the normal anatomical components, but fails to develop to normal size. CPH is extremely rare. More commonly, pulmonary hypoplasia occurs secondary to other anomalies, such as intrauterine compression of the developing lungs (diaphragmatic hernia, tumor, pleural effusion, skeletal anomalies, tracheobronchial stenoses), oligohydramnios, and impaired fetal breathing movements secondary to phrenic nerve agenesis or neuromuscular diseases. The compressive lesions may lead to unilateral hypoplasia, while systemic causes and CPH most often result in bilateral hypoplasia, which is generally lethal shortly after birth. Respiratory distress usually manifests within the first 5 minutes after birth, which reflects on the Apgar scores. Mechanical ventilation with highest oxygen concentrations and ventilator pressures is required to initially maintain reasonable arterial saturations. Nevertheless, most infants deteriorate further and die of respiratory failure (on average 9 hours after birth). Only a few infants survive and are discharged home from the hospital. Small clear lungs, pneumothoraces, and bilaterally raised diaphragms are considered diagnostic radiologic features for CPH. Most often, the ratio of lung weight to body weight is decreased, although secondary (ventilator-induced) lung changes may result in increased lung weight.

Unilateral hypoplasia may cause recurrent pneumonia and/or hypoxemia. Patients may require pulmonary lobectomy or pneumonectomy and are at risk for pulmonary barotrauma, pneumothorax, pneumomediastinum, or interstitial emphysema on either side. Persistent pulmonary hypertension of the newborn may be present and lead to right-to-left shunting through a persistent ductus arteriosus or patent foramen ovale with hypoxemia. Treatment with nitric oxide has been used successfully in some patients. It is obvious that these patients are at extremely high risk and should not be brought to the operating room until they have been stabilized, which probably is possible only in patients with milder forms of this disease.