What happens if a cast is applied too tightly?

When a cast is applied too tightly, the primary concern is the potential for circulation issues, which is accurately represented by the selected answer. When the cast compresses the soft tissues beneath it, it can impede blood flow, leading to complications such as swelling, numbness, tingling, or even severe conditions like compartment syndrome. These issues arise because the growing tissues require adequate blood supply, and a constrictive cast can prevent this, causing pain and potentially irreversible damage if not addressed promptly.

The other options do not adequately address the immediate complications associated with a tightly applied cast. A cast breaking is more related to the material's integrity rather than its tightness. Although a cast might loosen over time due to various factors, this is not a direct consequence of being too tight initially. Similarly, while waterlogging may concern cast retention and integrity, it is not relevant to tightness issues and their immediate effects on circulation. The correct understanding focuses primarily on the risk of compromising blood flow and the health of the tissues within the cast.