The way we breathe is strongly linked to the way we feel. When relaxed, we breathe slowly, and when anxious we breathe more quickly.
When we inhale we take in oxygen (O2), creating a waste product carbon dioxide (CO2) when we breathe out. With relaxed breathing, the levels of O2 and CO2 we produce are balanced, allowing us to function efficiently. Exercise too leads to an increase in breathing rate to take in more O2 to fuel the muscles, thereby producing more CO2 being expelled, and the O2/CO2 levels are balanced. However, when we are anxious our breathing rate increases and this same process applies but our bodies are not working any harder ie we are not necessarily exercising and not using up any extra O2 and thus the CO2 level in blood concentration drops, creating a state of alkalosis. This is why we feel light-headed, tingly, clammy and sweaty.