Final answer:
The second nurse should rotate in as compressor and resume chest compressions.
Step-by-step explanation:
When a second nurse arrives after the first nurse has delivered 30 chest compressions, the second nurse should rotate in as the compressor and resume performing chest compressions. This is important to maintain the circulation of blood within the patient's body and continue delivering the necessary pressure on the sternum to manually push blood into the pulmonary and systemic circuits. At this stage, the emphasis is on performing high-quality chest compressions rather than providing artificial respiration.