# Breathe through your nose The nose filters, warms and moistens the air so that it becomes more suitable for the lungs. It also increases the inhaled air's levels of nitric oxide, which your smooth muscles need, and regulates air flow. When you breath by the mouth, you tend to overbreath: you exhale too much CO2, which leads to hypocapnia, a lack of CO2 in the blood. A 2.5% drop in partial pressure of arterial CO2 reduces bloodflow to the brain by 2%. Furthremore, while red blood cells are almost always saturated with oxygen, their ability to release it is related to acidity and CO2 concentration — this is called the Bohr effect. The more CO2 in your blood, the better the circulation of oxygen. Slowly breathing through the nose can also help to increase your heart rate variability (see [[Slow down your breathing to improve your willpower]]). Finally, mouth breathing has been linked with reduced IQ, learning difficulties, and poor facial structure. --- ## 📚 References - [[@whativelearnedLessBreathBetter2017|LESS Breath: Better Health? | Mouth Breathing vs. Nasal Breathing]]