Which symptom may indicate a casualty has an open chest wound?

Coughing up blood is a significant symptom that may indicate a casualty has an open chest wound, particularly if air has entered the pleural cavity. This condition can result from a penetrating injury that compromises the chest wall or the lung. When there is an open chest wound, particularly a sucking chest wound, air can enter the pleural space, potentially causing a pneumothorax. If the lung is also damaged, alveoli may rupture, and blood can escape into the airways, leading to the patient coughing up blood, also known as hemoptysis.

Other options, while they can be associated with various medical conditions, do not specifically signal the presence of an open chest wound. Loss of vision can relate to head injuries or eye trauma but does not indicate a chest injury. Headaches might arise from various sources, including dehydration or strain, and excessive sweating could indicate a general state of shock or distress but is not directly indicative of a chest injury. Therefore, coughing up blood is the most relevant and telling symptom in this scenario.