Which of the following actions is essential to perform if someone is experiencing a secondary cardiac arrest?

When someone is experiencing a secondary cardiac arrest, the immediate step that must be taken is to perform CPR. Secondary cardiac arrest can occur due to factors such as respiratory failure, drowning, or trauma, where oxygen levels are compromised and lead to a sudden cardiac event. Administering CPR is critical in these situations as it helps to maintain blood flow to vital organs, particularly the brain and the heart.

CPR consists of chest compressions and rescue breaths, which together support the circulation of oxygenated blood during the critical minutes before advanced medical help arrives. The technique aims to restore effective heart function and can significantly improve the chances of survival and recovery for the victim.

The other actions listed, such as attempting to revive with water, applying cold compresses, or encouraging deep breathing, are not effective for treating cardiac arrest and do not provide the necessary support to the victim's circulatory system during such an emergency. In contrast, starting CPR promptly provides essential life-saving assistance that can bridge the gap until emergency medical services arrive.