Final answer:
In the case of a pediatric patient with a pneumothorax, air accumulates in the pleural cavity, which surrounds the lungs within the thoracic cavity. This can lead to the lung collapsing and require immediate medical care.
Step-by-step explanation:
If a pediatric patient has a pneumothorax, there is an accumulation of air in the pleural cavity. This is the space surrounding each lung, located within the thoracic cavity. The pleural cavity normally contains a small amount of lubricating fluid to allow the lungs to move smoothly during respiration. However, when there's a pneumothorax, air enters this space and can cause the lung to collapse, resulting in breathing difficulties. The accumulation of air in the pleural cavity is not normal and requires prompt medical attention.