You breathe without thinking because your body does it for you automatically. But things can
change your breathing pattern and make you feel short of breath, anxious, or ready to faint. When this happens, it’s called hyperventilation, or overbreathing.
That’s when you inhale much deeper and take much faster breaths than normal. This
deep, quick breathing can
change what’s in your blood. Normally, you breathe in oxygen and breathe out carbon dioxide. But when you hyperventilate, the carbon dioxide levels in your bloodstream
drop too low. You’ll notice it right away because you’ll start to feel sick.