Final answer:
When an adult arrest is unwitnessed or if EMS arrival is delayed by more than 4 minutes, the rescuer should begin immediate CPR. Early initiation of CPR can greatly improve survival rates and reduce the risk of brain damage. It is important to attempt resuscitation even if the person has been unconscious in water due to the potential effectiveness of CPR in these situations.
Step-by-step explanation:
If an adult arrest is unwitnessed, or EMS arrives more than 4 minutes after the time of arrest, the rescuer should begin immediate cardiopulmonary resuscitation (CPR). According to the American Heart Association guidelines, if you are alone with an unresponsive adult who has no obvious signs of life, it is crucial to provide CPR immediately.
The delay in EMS arrival can significantly impact the victim's survival chances, so performing CPR is the best way to support them until professional help arrives. It's worth noting that starting CPR within minutes can greatly increase the chances of survival and reduce the risk of brain damage.
Additionally, it's important to dispel the myth that it is too late to save someone who is unconscious in the water. If the person is rescued with an intact airway due to the protective laryngospasm which prevents water from entering the lungs, CPR can be highly effective. Rescuers should, therefore, start CPR as soon as possible, even if the cardiac arrest has caused the heart to stop beating. While brain cells start to die after about six minutes without oxygen, early CPR can make a significant difference in outcomes, particularly in cases of cold-water immersion where survival rates are higher.