ELi5: Why is it often recommended to breathe in through your nose and out through your mouth?
In: Biology
The short answer is it is a form of controlled breathing when people are anxious or in distress. A lot of people experience shortness of breath or will hyperventilate when they feel anxious. By having the person focus on how they breathe with simple instructions they can allow the anxiety to pass.
The other use is when people are on oxygen through a nasal cannula. COPD patients are often on oxygen chronically and feel short of breath often. Coaching them to breathe in through the nose and put through the mouth has a dual purpose. In through the nose because that’s where the oxygen is coming in. Out through the mouth (thru pursed lips) to cause back pressure on the lungs to keep them inflated on exhalation. This is really only important to people with lung disease however. Really it comes down to directing people’s focus off what is causing anxiety to work them through it.
the nose adds moisture to the air, the nose warms it up, and you don’t look like a caveman. the term “mouth breather” is a thing.
The nose and sinuses are specifically evolved to increase air temperature also to moisten and filter the air before it enters the lungs. This is important for the health and comfort of your lungs. That explains the breathing in part. But why out your mouth?
Well, because the sinuses are gory to trap all the filter stuff… also because they are narrow, breathing out in a sudden relaxation of the diaphragm results in blowing that mucus out and making your nose runny. It also forces pressure on the lungs by backing up the air slightly at the nose and increased pressure from a relaxed diaphragm. (Your breathe muscle).
So, by exhaling thru the mouth you can let air quickly leave the lungs without runny noses or increased pressure. This helps the body relax without instinct reflexes of increased lung pressure.
In thru the filter straw, out thru a drain.
Breathing nasally in general has already been covered, but it’s also important for a different reason during exercise. Nasal inhalation during exercise helps you control the speed and depth of your breathing, in order to avoid hyperventilating or not getting enough oxygen during aerobic activities like sprinting or biking.
Also, if you have exercise-induced asthma, nasal breathing can reduce your risk of setting off a flare-up by warming and moistening the air before it hits your lungs, which limits the irritation caused by huffing and puffing dry air through the mouth.
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