Chest IN & tummy OUT
In normal young children
, both the chest and tummy expand when breathing in.
With paradoxical breathing, the tummy expands when breathing in, but the chest gets sucked inward (downward). Paradoxical breathing can be normal in babies & toddlers because their chest cages are still "soft". After age 2-3 years, normal toddlers (without airway restriction) usually don't have paradoxical breathing.