Improved pulmonary function after surgical reduction of congenital diaphragmatic hernia in lambs

Modern trends are toward delayed surgical reduction of congenital diaphragmatic hernia. This study was conducted to verify the hypothesis that the "ease" of ventilation found in the authors' postoperative experience in infants with congenital diaphragmatic hernia (CDH) is associated with postsurgical improvement in pulmonary mechanics.

Very severe CDH was surgically induced in utero at 90 days' gestation in 31 lambs. At birth pulmonary mechanics (PeDS-Lab) was measured in these preterm lambs with (n = 24) and without (n = 7) early surgical reduction, and in eight non-CDH controls over the same period; functional residual capacity (FRC) also was obtained from 14 of the 31 CDH lambs (seven reduced animals and seven unreduced ones). Management excluded aspiration from the thorax and insertion of chest drains.

After 30 minutes of life CDH animals with early surgical reduction demonstrated significantly greater improvement in lung volume, pulmonary mechanics, and oxygenation than those without reduction: FRC, 235% versus 19%; compliance, 57% versus 14%; minute ventilation, 71% versus 30%; and PO2, 143% versus -15%. Over the same period, in preterm controls without CDH, only the compliance varied significantly, demonstrating a 32% increase.

Based on the mechanics of breathing in these lambs, the authors speculate that neonates with CDH could benefit from early surgical repair because of improvement in pulmonary function, provided extra care is taken to prevent pulmonary overdistension.