How/why does hyperventilation sometimes lead to syncope?

See below: Welcome hypervent can cause alkalosis of the body mess up acid base can cause you to faint.

Hyperventilation: Hyperventilation causes your body to eliminate the amount of carbon dioxide, which is a powerful vasoconstrictor. By causing vasoconstriction you reduce blood flow and oxygen delivery which can lead to fainting or syncope.

Carbon dioxide: This is the main "driver" for us to breathe. Co2 levels in the brain cause the respiratory center to signal breathing. When you hyperventilate you blow off a lot of co2 and the brain senses no need to breathe. Another driver is oxygen but since your o2 levels be high, the brain senses you have enough o2.