Nasal and oral breathing both serve the purpose of respiration, but they differ in their physiological process. Nasal breathing involves inhaling and exhaling through the nose. In mouth breathing, on the other hand, air is passed through the oral cavity into the wider respiratory tract.
What is nasal and mouth breathing?
Nasal and mouth breathing both serve the purpose of respiration, but they differ in their physiological process. Nasal breathing is physiological breathing. This means that a healthy person breathes in and out through the nose when at rest. When there is an increased demand for oxygen and thus also for breathing air, e.g. during physical activity, mouth breathing can also be physiological. Causes of permanent and thus pathological mouth breathing include polyps, colds, malocclusion of teeth and jaws, allergies, or an incorrect resting position of the tongue. During nasal breathing, the respiratory air is drawn in through the nostrils and directed into the nasal passages. It slides along the nasal conchae and then passes through the pharynx into the trachea, bronchi and finally into the lungs. There, gas exchange takes place. The exhaled air, which contains carbon dioxide, passes through the bronchi and trachea, down the throat and into the nasal passages, and is then exhaled through the nostrils. Nasal breathing normally occurs with the mouth closed. At physical rest, breathing does not occur simultaneously through both nostrils. More or less air flows through the nostrils alternately, giving the nostril with the reduced airflow time to regenerate the mucosa. This process is also known as the nasal cycle. In mouth breathing, the breathing air is drawn in through the mouth. The air is thus directly in the oral cavity, completely omitting the path via the nasal passages and turbinates. The remaining path of the respiratory air coincides with the path during nasal breathing. From the oral cavity, the air passes through the pharynx and lower airways to the lungs.
Function and task
The physiological form of breathing in humans is nasal breathing. There are several reasons for this. The nasal cavities and turbinates are lined with nasal mucosa. The nasal mucosa is crisscrossed by many vessels and covered with a layer of cilia. The cilia beat toward the throat about 500 times per minute. Inhaled foreign bodies and pathogens stick to the mucous layer of the mucosa and are then transported by the cilia towards the pharynx. There they are swallowed with the saliva and rendered harmless by the stomach acid. This prevents the foreign substances from entering the lungs and, in the worst case, causing an infection there. Due to the many vessels, the mucous membrane is very well supplied with blood and therefore warm. Cold air coming in through the nose is warmed by the mucous membrane. This protects the lungs and bronchi from excessively cold air. In addition, the mucous membranes ensure that the air breathed is moistened with every breath. Nasal breathing also stimulates the olfactory nerve. So-called olfactory cells are embedded in the mucous membrane. When we breathe in through the nose, odor molecules reach the mucous membrane, enabling us to perceive a wide variety of odors. Another advantage of nasal breathing is that nitric oxide, which is produced in the sinuses, reaches the lungs together with the air we breathe when we inhale. Nitric oxide can destroy viruses, parasites and degenerate cells in the airways and lungs. In addition, it apparently plays a role in pain perception, sleeping and learning. Nitric oxide also causes increased oxygen to be released from hemoglobin in the lungs. The same is true for carbon dioxide. A high carbon dioxide content promotes the uptake of oxygen in the lungs. This is called the Bohr effect. The nasal cavity and the paranasal sinuses belong to the so-called respiratory dead space. This is where increased carbon dioxide accumulates. When inhaled through the nose, this is transported into the lungs. Since the air bypasses the nasal cavities during mouth breathing, less carbon dioxide also reaches the lungs, making it more difficult for the lungs to absorb oxygen. Nasal breathing results in 10-15% higher blood oxygen saturation compared to mouth breathing. In addition, nasal breathing appears to activate more of the parasympathetic nervous system. The parasympathetic nervous system is part of the autonomic nervous system. It controls most of the internal organs. It dampens the heartbeat and is responsible for rest and sleep.It is therefore also called the resting nerve. The counterpart of the parasympathetic nervous system is the sympathetic nervous system, the fight-or-flight nerve. It activates the body and leads to a stimulation of the cardiovascular system. Studies have shown significantly higher sympathetic activity during mouth breathing.
Diseases and ailments
Nasal obstruction can have several causes. In adults, enlargement of the inferior turbinate is present in many cases. A crooked nasal septum can also cause nasal obstruction. Less common causes are polyps, tumors or injuries. If children can no longer breathe properly through the nose, a foreign body should always be considered. Certain medications, such as some antidepressants, hypertensives and contraceptives, can also result in nasal airway obstruction. The same applies to long-term use of decongestant nasal drops or nasal sprays. The drops initially cause the nasal mucosa to swell, but as soon as the effect wears off, there is reactively more filling of the vessels and thus even more swelling than before use. The most common reason for obstructed nasal breathing is rhinitis, i.e. a common cold. This can be bacterial, viral or allergic in origin. Acute or chronic inflammation of the sinuses can also make nasal breathing so difficult that additional mouth breathing is required. Predominant mouth breathing can lead to aerophagia. Aerophagy is the term used to describe excess air in the stomach and intestines. The result is bloating, abdominal pain, and increased belching.
