A3,480-g male infant, born to a gravida 4, para 2 mother, was delivered via primary cesarean section because of a footling breech presentation. The delivery was 18 days after the estimated date of confinement. The infant's Apgar scores at one and ten minutes were 4 and 8, respectively.
Eight hours after delivery, a respiratory rate (RR) of approximately 100/min developed, but he was not cyanotic. A chest roentgenogram (Fig 1) showed a left superior mediastinal mass. A barium esophagram showed no esophageal impingement or displacement. Arterial blood gas levels were normal.
At 72 hours of age, because of persistent tachypnea and the mediastinal mass, the infant was transferred to Yale-New Haven (Conn) Hospital for evaluation of his condition. Physical examination revealed an RR of 80/min during crying, 40 to 50/min after crying. Heart rate was 138 beats per minute. On auscultation, no cardiac murmurs were heard, and the lungs