What is NOT a sign of a chest injury?

Coughing up blood, severe pain, and difficulty breathing are all indicators that suggest the presence of a chest injury. These signs can point to serious conditions such as rib fractures, pneumothorax, or internal bleeding, which could arise from trauma or injury to the thoracic area.

In contrast, a fever is not typically a direct sign of acute chest injuries. While a fever may indicate infection or inflammation in the body, it is not specific to chest trauma. This differentiates it from the other signs, which are directly related to physical damage or distress in the chest region. Thus, the presence of a fever does not necessarily imply a chest injury, making it the correct choice for this question.