Which is a vital step to perform before ventilating during rescue breathing?

Before initiating rescue breathing, opening the airway is crucial to ensure that air can properly flow into the lungs. This step is essential because any blockage, such as the tongue or foreign objects, can hinder effective ventilation. By positioning the patient correctly—typically using the head-tilt, chin-lift maneuver—you create a clear passageway for air to enter the lungs.

While assessing responsiveness and ensuring the availability of oxygen are important parts of the overall assessment and response process in emergencies, those actions occur at different stages. Preparing AED settings is relevant but not directly related to the immediate action of performing rescue breathing. Thus, the vital step of opening the airway ensures that the rescuer can provide effective breaths, significantly improving the chances of oxygenating the patient adequately.