What symptom would warrant immediate intervention for a child with congenital diaphragmatic hernia?

Sudden difficulty breathing is a critical symptom that necessitates immediate intervention for a child with congenital diaphragmatic hernia. This condition can lead to significant respiratory distress due to the herniation of abdominal contents into the thoracic cavity, which can compress the lungs and impede normal respiratory function. If a child experiences sudden difficulty in breathing, it indicates a potentially life-threatening situation that may require urgent medical evaluation and interventions such as supplemental oxygen, mechanical ventilation, or other emergency treatments to stabilize the child's respiratory status.

In contrast, persistent coughing might indicate a respiratory issue but does not necessarily create an acute scenario requiring immediate action. Increased appetite and sleeping too much are less concerning symptoms in the context of congenital diaphragmatic hernia and do not signal a critical emergency. Thus, sudden difficulty in breathing stands out as the most urgent and dangerous symptom requiring swift medical response.