"A" is for AIRWAY. It is normal for an infant to take shallow and rapid breaths, so carefully look, listen and feel for breathing. If you cannot detect any signs of breathing, the tongue may be obstructing the infant's airway.
Although the head tilt/chin lift technique is similar to adults and children, when clearing an infant's airway it's important not to tilt the head too far back. An infant's airway is extremely narrow and overextending the neck may actually close off the air passage.
Tilt the head back into what is called the "sniffer's position" - far enough to make the infant look as if he is sniffing (Figure 1).
If the victim is still not breathing on his own, you will have to assist him Breathing