If you see an entrance wound on a casualty's chest and no other injuries, what is the first action to take?

The first action to take when you observe an entrance wound on a casualty's chest is to seal the chest wound and check for other wounds on their back. This step is critical because an open chest wound can lead to a pneumothorax, where air can enter the chest cavity and potentially compromise the casualty's breathing. Sealing the wound helps to prevent air from entering and allows the lungs to function more effectively.

Additionally, checking for wounds on the back ensures a thorough assessment. Sometimes, exit wounds are present on the opposite side of the body, and failing to address these could lead to further complications. By securing the chest and ensuring there are no additional injuries, you are providing immediate life-saving care and preparing the casualty for further treatment.

Other options, such as administering CPR, applying a tourniquet, or transporting the casualty immediately, might not address the immediate threat posed by the chest wound. In the case of an open chest injury, managing the wound effectively takes precedence over these actions.