Prediction of outcome by computer-assisted analysis of lung area on the chest radiograph of infants with congenital diaphragmatic hernia

Abstract

Background/Purpose: Pulmonary hypoplasia is a major cause of mortality and morbidity in infants with congenital diaphragmatic hernia (CDH). Pulmonary hypoplasia is characterized by low volume lungs, and affected infants are likely to have a low lung area on their chest radiograph. The authors assessed whether, in CDH infants, computer-assisted analysis of the chest radiograph lung area gave an accurate indication of lung volume, and if a low lung area was a better predictor of poor outcome (death or oxygen dependency at 28 days) than other test results.Methods: Comparisons were made of the radiographic lung area derived by computer-assisted analysis and lung volume, assessed by measurement of functional residual capacity (FRC) on day 1 before surgical intervention and on the first postoperative day. Compliance was measured, and the maximum and modified ventilation indices and maximum PaCO2 also was noted. Twenty-five CDH infants with a median gestational age of 38 weeks were studied; 18 had FRC measurements preoperatively.Results: Both preoperatively and postoperatively, the lung areas and FRCs correlated significantly (r = 0.51, P < .05; r = 0.76, P < .02, respectively). Eleven infants had a poor outcome (5 infants died without an operation); that group preoperatively differed significantly from those with a good outcome with respect to having a lower compliance (P < .02) and higher maximum ventilation index (P < .01) and maximum modified ventilation index (P < .05). Only postoperatively did infants with a poor outcome versus good outcome have a significantly lower lung area (P < .05); they also had a lower increase in lung area preoperatively to postoperatively (P < .01). Receiver operator characteristic curves were constructed; comparison of the areas under the curves showed that preoperatively, a low compliance and high ventilation index were the best predictors of poor outcome. Postoperatively, a low lung area performed as well as the ventilation indices.Conclusion: Computer-assisted analysis of the lung area on the chest radiograph is useful in predicting outcome in CDH infants postoperatively but not preoperatively.