A 9-year-old has suddenly collapsed. After confirming that the scene is safe, a single rescuer determines that the child is in cardiac arrest, shouts for nearby help, and activates the emergency response system by using his mobile device. He immediately begins performing high quality CPR. Two additional rescuers immediately arrive to assist in the resuscitation attempt.Two rescuers begin high-quality CPR while the third rescuer leaves to get the AED. What action supports 2-rescuer CPR?