The effects of intrapleural pressure on respiratory insufficiency.

Newborns with congenital diaphragmatic hernia generally survive operative repair of the hernia but develop progressive respiratory insufficiency that proves fatal. One cause for the progressive respiratory insufficiency may be the overexpansion of the contralateral lung. It is postulated that the overexpansion occurs due to the empty space created by the lack of expansion of the hypoplastic lung on the side of the hernia. To test this theory, an animal experiment was devised to mimic the postoperative state in patients with diaphragmatic hernia. It was concluded that (1) A decrease in intrapleural pressure below normal in an empty hemithorax causes the opposite lung to overexpand into the empty hemithorax in neonatal Beagle puppies. (2) The overexpansion resulted in progressive respiratory insufficiency. (3) Increasing the intrapleural pressure by insufflation of air into the empty hemithorax stopped the overexpansion of the contralateral lung. (4) By not allowing the contralateral lung to overexpand, progressive respiratory insufficiency was prevented. (5) This may be a useful technique in neonates with congenital diaphragmatic hernia.