Lack of oxygen in the brain for 5 to 10 minutes results in permanent brain damage.
Doctors typically refer to two distinct forms of oxygen deprivation: anoxic brain injuries occur when the brain is deprived of oxygen due to sudden cardiac arrest, choking, strangulation, and other sudden injuries. Hypoxic brain injuries occur when the brain receives less oxygen than it needs but is not completely deprived of oxygen. Because the effects of the two injuries are similar, many brain experts use the terms interchangeably.
A few seconds of oxygen deprivation won't cause lasting harm, so a child who holds his breath in frustration, a combatant choked unconscious during a Jiu-Jitsu, and a diver who needs a few extra seconds to come up for air is unlikely to experience brain damage. The precise timeline of anoxic brain injuries depends on several personal idiosyncrasies, including overall brain and cardiovascular health, as well as the level of blood oxygenation at the time of injury.
Generally speaking, injuries begin at the one-minute mark, steadily worsening thereafter:
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, and lasting brain damage becomes more likely.
At five minutes, death becomes imminent.
At 10 minutes, even if the brain remains alive, a coma and lasting brain damage are almost inevitable.
At 15 minutes, survival becomes nearly impossible.