“Hyperventilation during a panic attack makes people feel like they don’t have enough oxygen, but actually they have plenty. Their red blood cells, carrying oxygen, remain fully loaded: 100 percent saturated. But all that heavy breathing lowers the concentration of carbon dioxide – the gas we exhale. We actually need a certain amount of carbon dioxide circulating in our blood; if the carbon dioxide is too low, the brain responds by squeezing and shrinking the small blood vessels.”
