And what about people like David Blaine or Tom Sietas? Sietas held his breath underwater for over 22 minutes (world record). I know they train for it like months and even years, but doesn’t holding your breath = no oxygen to brain?
Permanent brain damage apparently occurs just after 4 minutes of lack of oxygen to the brain, so why are freedivers left generally unscathed after 8 or 10 minutes without air?
In: Biology
Divers can breathe in as much air as possible before diving. That air will supply them with oxygen for a while. Also they can hyperventilate (breathe in and breathe out strongly and rapidly for a while) before diving, so that their blood will become saturated with oxygen, keeping the brain oxygenated even if there’s no more air.
If the brain stops getting its oxygen the person usually loses conscience within mere seconds (like if an airplane depressurizes while at high altitude). Obviously divers don’t want that to happen, so their brain keeps getting oxygen. If a diver has lost conscience they’d quickly drown. The 4-6 minutes survival time means that oxygen supply to the brain has to be restored within that timeframe to avoid death.
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