Final answer:
A pneumothorax can cause a problem with preload by restricting blood flow to the heart.
Step-by-step explanation:
A pneumothorax is a condition where air accumulates in the pleural space, causing the lung to collapse. This can affect preload, which refers to the amount of blood in the heart before it is pumped out. When a pneumothorax occurs, the collapsed lung puts pressure on the major blood vessels in the chest, restricting blood flow to the heart. As a result, the heart receives less blood, leading to a decrease in preload.