It causes a decrease in the amount of a gas in the blood (called carbon dioxide, or CO2). This decrease may make you feel lightheaded, have a rapid heartbeat, and be short of breath. It also can lead to numbness or tingling in your hands or feet, anxiety, fainting, and sore chest muscles.

Why does hyperventilation cause you to pass out?

Hyperventilation. A person who is hyperventilating is taking fast breaths. Carbon dioxide (CO2) levels in the blood fall, causing blood vessels to narrow. Blood flow to the brain decreases, making a person faint.

What happens if you pass out from hyperventilation?

A person who is hyperventilating is taking fast breaths. Carbon dioxide (CO2) levels in the blood falls, causing blood vessels to narrow. Blood flow to the brain decreases, making a person faint.