The following is an excerpt from the brand new book, THE BREATHING CURE: Develop New Habits for a Healthier, Happier, and Longer Life Hardcover by Patrick McKeown. Available to purchase here.
In texts about the anatomy and physiology of breathing, the respiratory tract is described as the path for air to travel from the nose to the lungs. The mouth doesn’t get a mention for one simple reason: despite common habits and preconceptions, our bodies are designed for nasal breathing. It has been said that breathing through the mouth is like eating through the nose.
I was a habitual mouth-breather throughout my childhood and into my early twenties. For all that time, I completely bypassed my nose.
Little did I know that the development of the lower half of the face and jaw is largely influenced by whether the mouth is open or closed during the formative years of childhood.
Prolonged mouth breathing even altered the structure of my face, resulting in a smaller nasal airway, high upper palate, underdeveloped jaw, and crooked teeth.
Although mouth breathing is a distortion of an intrinsic bodily function, it is incredibly common. A 2008 study of 370 randomly selected children between three and nine years old, all from Abaeté, Brazil, found that 55% were mouth breathers. In 2010, a Portuguese study examined the incidence of mouth breathing in children aged between six and nine.
The results of 496 parental questionnaires revealed that nearly 57% of the children breathed through their mouths. The frequency of mouth breathing among adults receives less attention, but one 2016 paper of more than 9,000 people from a town in Japan reported that 17% breathed through their mouths.
As we’ll see, mouth breathing doesn’t just disrupt the growth of the face and teeth. It is also a significant factor in a variety of problems, ranging from obstructive sleep apnea to high blood pressure, a reduced quality of life and fatigue.
What’s So Great About Breathing Through the Nose?
Nasal breathing performs at least 30 functions on behalf of the body. One of the most important of these is oxygenating the blood, organs, and cells.
Because the nostrils are significantly smaller than the mouth, nose breathing while awake creates about 50% more resistance to airflow than mouth breathing.
This results in a 10% to 20% greater oxygen uptake in the blood. Breathing through the nose filters and warms the air before it enters the lungs, and the resistance created by nasal breathing makes the breathing slower and deeper, engaging the diaphragm and calming the mind.
Contrary to the advice of many sports coaches, it is not a good idea to breathe in through the nose and out through the mouth. In one study where subjects were instructed to breathe that way, nasal stuffiness increased by 200%. What’s more, congestion persisted for 10 minutes after the challenge ended.
Even during only exhaling, mouth breathing causes the loss of heat and water. To be precise, 42% more water is lost when exhaling through the mouth than through the nose.
This loss of moisture and warmth causes inflammation, stuffiness, and dehydration—which makes breathing more difficult. Once your nose is blocked, you can find yourself needing to breathe through your mouth, and so mouth breathing can become a habit.
It is best to breathe both in and out through the nose.
This not only facilitates oxygenation, it also helps prevent nasal congestion. When your nose is clear, breathing is easier during both rest and exercise.
It may sound contradictory that nasal breathing helps clear your nose. After all, most people breathe through their mouth because their nose is blocked.
However, when your nose is blocked, the counterintuitive act of breathing through the nostrils helps keep the airways clear, prevents dehydration, and improves breathing volume.
When you inhale or exhale through the nose, breathing is slower due to the extra resistance created by the smaller airway.
This resistance to exhaling in nasal breathing helps maintain lung volume. Even after maximum exhalation, there is always some air left in the lungs. This air is called residual volume.
When the nose is blocked, forcing mouth breathing, total lung capacity and residual volume both decrease significantly.
To understand why this residual volume is important, think about inflating a balloon. The most difficult part is blowing the initial volume of air to get the balloon going.
However, if you allow an inflated balloon to deflate just partway, it is much easier to reinflate it than when you let all of the air escape.
In the same way, if your lungs were completely emptied of air after every exhalation, breathing would require more effort, the lungs would collapse, and strenuous activity would be impossible.
Every time you exhale through your mouth, you may breathe out more air than necessary. That means that every inhalation takes extra effort. Breathing becomes much harder work than it needs to be.
During nasal breathing, several things happen differently than they do during mouth breathing:
When breathing through the nose, the lungs can extract oxygen from the air during both exhalation and inhalation. Although the oxygen supply to the air sacs in the lungs is renewed during the inhalation, oxygen diffuses continuously into the blood, because the small size of the nostrils helps create a flow of air back into the lungs even during nasal exhalation.
The slower nasal exhalation gives the lungs more time to extract the oxygen. When this optimal blood gas exchange occurs, carbon dioxide (CO2) is processed properly, and blood pH remains balanced.
Air inhaled through the nose passes through the nasal mucosa. This stimulates reflex nerves that control regular breathing. (One reason mouth breathing can lead to snoring, sleep apnea, and irregular breathing patterns is that it bypasses this nasal mucosa.)
The air passes through the nose, which houses the olfactory bulbs. Those are connected to the hypothalamus, the part of the brain linked to many automatic functions such as heartbeat, blood pressure, appetite, thirst, and homeostasis.
In nasal breathing, the sinuses produce nitric oxide (NO), which is necessary for regulating inflammation in the airways and in the body’s defense against airborne pathogens, viruses, and bacteria.
Patrick McKeown is an internationally renowned breathing coach, author and speaker. He is creator of Oxygen Advantage®, founder of Buteyko Clinic International and a fellow of the Royal Society of Biology in the UK. Published works include research in the Journal of Clinical Medicine, and books including The Breathing Cure.
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