When does hypoxia start at low oxygen in humans?

Hypoxia, by definition, is when the brain is deprived oxygen. Low oxygen to humans can be for many reasons. Hypoxia can start as low oxygen in humans by the improper blood oxygenating. Such things as a heart attack, choking, asthma, stroke, are affected by the brain not receiving the proper oxygen to function at its fullest capacity. It is low blood oxygen since the blood is responsible for transporting the oxygen to the brain.

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