"A" is for AIRWAY. If the victim is unconscious and is unresponsive, you need to make sure that his airway is clear of any obstructions. If you determine that the victim is not breathing, then something may be blocking his air passage. The tongue is the most common airway obstruction in an unconscious person.

With the victim lying flat on his back, place your hand on his forehead and your other hand under the tip of the chin (Figure 1). Gently tilt the victim's head backward. In this position the weight of the tongue will force it to shift away from the back of the throat, opening the airway (Figure 2).

If the person is still not breathing on his own after the airway has been cleared, you will have to assist him breathing