Your baby stopped breathing, requiring some form of stimulation or resuscitation to recover
Your child is breathing too fast: above 50 times per minute in babies and infants and above 40 times per minute in toddlers
There are abnormal breath sounds, like an audible sound on taking in a breath (stridor) or an audible whistling noise when breathing out (wheezing).
There are any of the following signs indicating that breathing has become hard work and that your little one may eventually tire: your baby struggles to finish the usual volume of a feed; the presence of chest wall indrawing (the soft tissues above the collar bones, between the ribs or below the ribcage sinks into the chest during breathing); use of the neck and/or abdominal muscles to breathe
There is a blue hue to lips, tongue or nails (very late sign - call the ambulance rather, as there is an urgent need for oxygen)