Unsuspected pulmonary vascular abnormalities associated with diaphragmatic hernia.

The pulmonary vasculature of 12 newborn infants who died with unilateral diaphragmatic hernias was studied. Four developed severe ventilatory insufficiency after birth and promptly died. Their lungs were both hypoplastic and airless dur to compression by displaced abdominal viscera and mediastinal shift. Corrective surgery permitted lung expansion and adequate ventilation for one to two hours in five infants. Subsequently, ventilatory insufficiency supervened and they died. Postoperative blood gases revealed a right-to-left ductus arteriosus shunt in one infant. Ten of the infants with hernias had a significantly greater mass of muscle in pulmonary arteries than did matched controls. This may partially explain the fetal-type circulatory infants.