eli5: why do most, if not all, breathing techniques specify ‘out through the mouth’?

Question

i can understand in ‘through the nose’, since dust and other bits can be blocked by the nose hairs and mucus, and apparently the air is more likely to warm up when passing through the nose first, reducing irritation of the throat.

but what difference, if any, does exhaling through the mouth make?

In: 676

Answer 1

Along with what others have said, it can help you exhale more CO2. We do this a lot with our COPD patients where we have them inhale through their nose and exhale through mouth like they’re blowing through a straw. This slows down the rate of exhalation allowing more CO2 to diffuse out of the bloodstream.