Final answer:
The most important intervention for the nurse to include in the 7-year-old boy's plan of care would be assisting the child to lie still during the chest x-ray.
Step-by-step explanation:
The most important intervention for the nurse to include in the 7-year-old boy's plan of care would be assisting the child to lie still during the chest x-ray. Respiratory distress indicates a potential problem with the lungs, and a chest x-ray can help diagnose the cause of the distress. To obtain accurate results, the child needs to lie still during the procedure. This intervention is crucial as it ensures that the x-ray captures clear images of the lungs, aiding in diagnosis and treatment planning.