As mentioned, your body is trying to help you when it goes into this state by supplying as much oxygen as possible.
Problem is, things are kind of kicking into hyperdrive to the point where it is no longer adaptive or conducive to good health. You’re actually not breathing out enough and as such, you are flooding the body with oxygen but expelling all your CO2. That’s a problem because your body needs CO2 in order to extract oxygen from red blood cells.
So, despite breathing an awful lot, your brain is now becoming starved of oxygen and as such, it is going to start shutting down. That’s why we faint!
So, to avoid this problem, you can try rebreathing. That means grabbing a paper bag and breathing into that. This way, you will use up the oxygen that’s in the bag and you’ll instead be recycling the CO2 – preventing the issue we just discussed.