What critical factor must be observed while performing rescue breathing?

Establishing an airway is crucial when performing rescue breathing because it ensures that the oxygen can effectively reach the lungs of the diver in distress. Without a clear airway, any attempt to deliver breaths will be ineffective, as air cannot flow into the lungs. This step involves positioning the head appropriately to open the airway, which may include tilting the head back or using a chin lift maneuver.

In rescue scenarios, if the airway is obstructed – whether by water, vomit, or a lack of proper positioning – the effectiveness of rescue breathing is significantly diminished. Therefore, securing an unobstructed airway is the first priority in successful ventilation efforts, ensuring that the individual receives the necessary oxygen to sustain life until further help can be administered or the victim can be revived. This foundational step is critical in emergency response and life-saving techniques in diving and similar rescue situations.