how soon will brain damage occur without oxygen and/or medical intervention?

Brain damage from lack of oxygen can begin very quickly. Generally, loss of consciousness may occur between 30 seconds to 3 minutes without oxygen. Brain cells start dying at about one minute of oxygen deprivation. At three minutes, neurons suffer more extensive damage, increasing the likelihood of lasting brain damage. By five minutes, the risk of severe injury becomes high, and death becomes imminent approaching 10 minutes without oxygen. After around 10 minutes, even if the brain remains alive, coma and lasting brain damage are almost inevitable. Survival beyond 15 minutes without oxygen is nearly impossible. The exact timing depends on individual factors like overall health and oxygen levels at the time of deprivation. Specialized training in breath- holding can extend this timeline significantly.