Pulmonary barotrauma in congenital diaphragmatic hernia: A clinicopathological correlation

Background/Purpose: The high mortality rate in congenital diaphragmatic her nia (CDH) has been ascribed to pulmonary hypoplasia and persistent pulmonar y hypertension of the newborn (PPHN). One of the principal treatment strate gies has been the use of hyperventilation to reverse ductal shunting, but t he wisdom of this approach is being questioned because of parenchymal lung injury from high inflation pressures. The authors hypothesize that the use of hyperventilation to reverse or prevent ductal shunting would result in v entilator-induced lung injury, which would be evident on postmortem examina tion. A retrospective review of clinical and autopsy information was conduc ted. Methods: Clinical and autopsy information gathered for a previously publish ed series of 223 infants with CDH presenting in the first 24 hours of life was reviewed. Autopsy and clinical data were analyzed from 68 of 101 nonsur vivors who died with severe hypoxemia. Results: Sixty-two of 68 cases (91%) had evidence of diffuse alveolar damag e and hyaline membrane formation, which was more evident in the ipsilateral lung. Forty-four (65%) infants had pneumothoraces, and 4 infants had inter stitial fibrosis. Pulmonary hemorrhage was seen in 35 cases (50 maximum pea k inspiratory pressure [mean +/- SD] was 40.4 +/- 7.9 cm H2O and lowest mod ified ventilatory index [respiratory rate X peak airway pressure] was 2323 +/- 836). The degree of pulmonary hypoplasia was evaluated by lung weight w ith the ratio of the observed combined lung weight to the expected lung wei ght based on birth weight and gestational age. The ratio based on birth wei ght was 57% +/- 25%, and the ratio based on gestational age was 60% +/- 26% . Twenty-one infants (35%) had nonpulmonary anomalies. The most significant was a 10% incidence of congenital heart disease. Apart from this, lethal n onpulmonary anomalies were rare. Conclusion: These results suggest that lung injury secondary to mechanical ventilation plays an important role in the mortality rate of patients with CDH, which may become increasingly significant when there is underlying pul monary hypoplasia. J Pediatr Surg 34:1813-1817. Copyright (C) 1999 by W.B. Saunders Company.