B

After intubation of a child with suspected congenital diaphragmatic hernia—suggested by respiratory distress, mediastinal shift, and scaphoid abdomen—the immediate priority is gastric decompression with a nasogastric tube to prevent further inflation of intrathoracic stomach and worsening cardiorespiratory compromise [Unal 1980 PMID 6109487; Paut 1996 PMID 8773870].