What is the best course of action if a responder suspects a cardiac arrest?

Starting chest compressions immediately is the best course of action when a responder suspects a cardiac arrest because time is critical in such situations. Cardiac arrest leads to the cessation of effective blood circulation, which can result in brain death and other organ failures within minutes. Chest compressions help maintain blood flow to vital organs, particularly the brain and heart, until professional medical help arrives or an automated external defibrillator (AED) can be used.

Initiating chest compressions promptly increases the chances of survival and improves outcomes for the patient. This is part of the "chain of survival" concept, which emphasizes the importance of early recognition and intervention in cases of cardiac arrest. Other options, such as administering oxygen without assessment or performing abdominal thrusts, are not appropriate responses in this scenario, as they do not address the immediate need for circulation and can lead to further complications. Waiting for the patient to gain consciousness is also not viable, as it may result in irreversible damage due to lack of oxygenated blood flow.