06/19/2012 05:53 pm ET Updated Jun 19, 2012

Clinically Dead: What Does Hosni Mubarak's Formerly Reported Condition Mean?

Former Egyptian ruler Hosni Mubarak is unconscious and on a respirator, according to Reuters, after previously being declared "clinically dead" by his doctors.

But what exactly does it mean to be "clinically dead?"

Clinical death occurs when the heart stops beating, thereby stopping the flow of blood to the brain, heart and body, according to the Sudden Cardiac Arrest Foundation.

Clinical death is actually the same as sudden cardiac arrest; a person will keep on being "clinically dead" unless he or she is able to be revived with CPR or a defibrillator. A person who is clinically dead can still be kept alive with a respirator, or another kind of life support.

Discovery reports that "actual" death occurs minutes after "clinical death," when the brain cells die because they are not receiving any oxygen. At this point, damage is permanent and irreversible.

Recently, ABC News reported on research from British scientists suggesting that people may still have consciousness even though they are clinically dead. The study included 63 people who had had a heart attack and were considered clinically dead, but were later revived. Four of those people said that they remembered having clear memories during the time of clinical death.

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