What other things can cause the chest x-ray appearance of hyper expansion/air trapping. ?

Hyper expansion: COPD, asthma, cystic fibrosis and other cystic lung diseases, some infections(RSV), and spurious chest X-ray finding due to large inspiratory excursion.

Depends on age: Causes of air trapping in children different than adults. Less than year of age respiratory syncytial virus (RSV) and other viruses. Congenital emphysema, cystic lung & aspiration occur in infants. Acute .Asthma affects young childen, adolescents, and adults.Cystic fibrosis usually seen in children, adolescents & adults with improvements in therapy living much longer. COPD mainly adult