Harry the swimmer is an oxygen loader who is going about it the wrong way

Harry has forgotten that It's the CO2 level, and not the O2 level, that causes a person to have the urge to breathe. In other words, once the CO2 level in the blood is high enough, the brain will trigger a breathing response, causing the person to try to gasp for air. Harry is jeopardizing his time and life because Hyperventilation itself reduces the carbon dioxide concentration of the blood to below its normal level, raising the bloods ph value, initiating constriction of the blood vessels which supply the brain, and preventing the transport of certain electrolytes necessary for the function of the nervous system.

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thanks bioman!