The rescue actions for cardiac arrest due to drowning differ from those for sudden cardiac arrest primarily because the underlying causes and immediate needs are different. For cardiac arrest caused by drowning, the main issue is lack of oxygen due to water filling the lungs, leading to severe hypoxia. The priority is to provide rescue breaths to supply oxygen and help expel water from the lungs, followed by chest compressions. This differs from sudden cardiac arrest, where the heart stops suddenly but blood is usually still oxygenated initially, so immediate chest compressions and defibrillation with an AED are the primary focus. Specifically:

• In drowning-related cardiac arrest, rescuers should start with rescue breaths (typically 5 initial rescue breaths), then alternate rescue breaths and chest compressions (e.g., 30 compressions and 2 breaths).
• In sudden cardiac arrest, rescuers focus immediately on high-quality chest compressions and rapid AED use, with rescue breaths if trained, but compressions are often prioritized.
• An AED can be used in both cases but typically after starting CPR in drowning cases.
• Rescue breaths are vital in drowning cases due to the respiratory cause, whereas in sudden cardiac arrest, oxygenated blood is usually still available making compressions and defibrillation most urgent.

These differences emphasize the need in drowning to restore breathing as well as circulation, while sudden cardiac arrest primarily requires restoring circulation by compressions and shock if needed.