The brain represents just 2% of body weight, yet it uses about 20% of the body's oxygen supply. Without it, the brain can't perform even the most basic functions. The brain relies on glucose to power neurons that control everything from conscious functions like planning and thought to automatic unconscious processes like heart rate and digestion.

Without oxygen, the brain's cells cannot metabolize glucose, and therefore cannot convert glucose into energy.

When your brain is deprived of oxygen, then the ultimate cause of brain death is inadequate energy to power the brain's cells.

•    Between 30-180 seconds of oxygen deprivation, you may lose consciousness.
•    At the one-minute mark brain cells begin dying.
•    At three minutes neurons suffer more extensive damage.
•    At five minutes death becomes imminent.
•    At 10 minutes even if the brain remains alive, a coma and lasting brain damage.
•    At 15 minutes survival becomes nearly impossible.