Final answer:
Cardiac arrest in children is most commonly due to respiratory failure, stemming from severe respiratory issues that lead to a lack of oxygen in the blood.
Step-by-step explanation:
Cardiac arrest in children is most commonly due to respiratory failure. Unlike adults, where cardiac arrest is often the result of a heart attack or other heart-related issues, in children, the primary cause is typically a severe respiratory problem that leads to a lack of oxygen in the blood, which in turn causes the heart to stop. Conditions such as respiratory infections, asthma, and obstruction of the airway can lead to respiratory failure in children. It is important to note that cardiac arrest in children can also be caused by congenital heart defects, but these are generally less common than respiratory causes.