Toddlers and Sleep Apnea info I found helpful:
The list of symptoms for OSA is long. The most telling signs are snoring and difficulty breathing while asleep, often characterized by pauses in breathing. (In a sleep lab, a pause is ten seconds or more without breathing.)
Don't jump to the conclusion that your child has sleep apnea if he snores, though; 1 to 3 percent of children have sleep apnea, while 7 to 12 percent of children snore, according to Gary E. Freed, D.O., a professor of pediatrics and director of the Pediatric Sleep Laboratory at Emory University School of Medicine in Atlanta. Likewise, it's possible to have sleep apnea without snoring.
You should be suspicious if your child breathes through his mouth most of the time (both at night and during the day), often coughs or chokes at night, is a restless sleeper, or sweats profusely when he's asleep.
Combined with any of the above symptoms, repeated night-wakings can be a sign of sleep apnea. Because children with sleep apnea have trouble breathing, they may stir more often, waking up to get the air they need.
If you think your toddler might have sleep apnea, look to his daytime behavior for more clues. Children with apnea are often sleep deprived, making them more prone to irritability, crankiness, and frustration. Your child may fall asleep at inappropriate times because he's so tired.
A child with sleep apnea is also more likely to have tonsil- or adenoid-related health problems. Your child may be growing more slowly than he should if he's not sleeping long enough to benefit from the growth hormones that are released at night. He may also not be growing properly if he works so hard to breathe at night that he's burning up his calories. "It's like running a marathon every night," explains Freed.