Final answer:
Perform defibrillation would take the highest priority if the patient became apneic and pulseless but the rhythm remained the same.
Step-by-step explanation:
If the patient became apneic and pulseless but the rhythm remained the same, the highest priority would be to perform defibrillation. Defibrillation is an emergency treatment that delivers an electric shock to the heart to restore its normal rhythm. This procedure is essential in cases of cardiac arrest, as it can help restart the heart and restore blood flow.