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Obligate nasal breathing describes a physiological necessity to breathe through the nose (or other forms of external nares, depending on the species) as opposed to breathing through the mouth.


Definition

The term may be misleading, as it implies that the organism has no choice but to breathe through its nose; however, it is also used to describe cases where effective breathing through the mouth is possible but not preferred. Alternatively, the term has been defined by some as the ability to breathe through the nose while swallowing. While this ability is a common trait of obligate nasal breathers, clearly this definition does not require that nasal breathing in any way be obligatory to the animal. Even in obligate nasal breathers such as horses, rabbits, and rodents, there is a potentially patent path for air to travel from the mouth to the lungs which can be used for endotracheal intubation. It has been suggested that obligate nasal breathing is an adaptation especially useful in prey species, as it allows an animal to feed while preserving their ability to detect predators by scent.


Animals

Horses are considered obligate nasal breathers. The respiratory system of the horse prevents horses from breathing orally. The
epiglottis The epiglottis is a leaf-shaped flap in the throat that prevents food and water from entering the trachea and the lungs. It stays open during breathing, allowing air into the larynx. During swallowing, it closes to prevent aspiration of food int ...
rests above the soft palate while the animal is not swallowing, forming an airtight seal. Oral breathing can only occur with significant anatomical abnormalities or pathological conditions. For example, denervation of the pharyngeal branch of the
vagus nerve The vagus nerve, also known as the tenth cranial nerve, cranial nerve X, or simply CN X, is a cranial nerve that interfaces with the parasympathetic control of the heart, lungs, and digestive tract. It comprises two nerves—the left and right ...
results in dorsal displacement of the
soft palate The soft palate (also known as the velum, palatal velum, or muscular palate) is, in mammals, the soft tissue constituting the back of the roof of the mouth. The soft palate is part of the palate of the mouth; the other part is the hard palate. ...
(DDSP), and it has been suggested that this leads to a clinical syndrome which may include oral breathing. However, significant respiratory dysfunction including airway obstruction is observed with DDSP, and the animal cannot function normally in this state. Rabbits, cats, and rodents are also obligate nasal breathers. Like horses, the normal anatomical position of the epiglottis causes it to be engaged over the caudal rim of the soft palate, sealing the oral pharynx from the lower airways. Air entering the mouth will not fully make it to the lungs. Even so, rabbits with advanced upper airway disease will attempt to breathe through their mouths. Many other mammals, such as dogs and adult humans, have the ability to breathe indefinitely through either the oral or nasal cavity.


Humans

According to Jason Turowski, MD of the
Cleveland Clinic Cleveland Clinic is a nonprofit American academic medical center based in Cleveland, Ohio. Owned and operated by the Cleveland Clinic Foundation, an Ohio nonprofit corporation established in 1921, it runs a 170-acre (69 ha) campus in Cleveland ...
, "we are designed to breathe through our noses from birth — it’s the way humans have evolved." This is because it is the job of the nose to filter out all of the particles that enter the body, as well as to humidify the air we breathe, add moisture to it, and warm it to body temperature. In addition, nasal breathing produces
nitric oxide Nitric oxide (nitrogen oxide or nitrogen monoxide) is a colorless gas with the formula . It is one of the principal oxides of nitrogen. Nitric oxide is a free radical: it has an unpaired electron, which is sometimes denoted by a dot in its ...
within the body while
mouth breathing Mouth breathing, medically known as chronic oral ventilation, is long-term breathing through the mouth. It often is caused by an obstruction to breathing through the nose, the innate breathing organ in the human body. Chronic mouth breathing ma ...
does not. Mouth breathing also leads to dry mouth, throat infections, a reduced sense of taste, and other chronic conditions. Nasal breathing is a research interest in
Orthodontics Orthodontics is a dentistry specialty that addresses the diagnosis, prevention, management, and correction of mal-positioned teeth and jaws, and misaligned bite patterns. It may also address the modification of facial growth, known as dentofacial ...
(and the related field of Myofunctional Therapy) and for biological anthropologists.


Infants

Human infants are commonly described as obligate nasal breathers as they breathe through their nose rather than the mouth. Most infants, however, are able to breathe through their mouth if their nose is blocked. There are however certain infants with conditions such as choanal atresia in which deaths have resulted from nasal obstruction. In these cases there are cyclical periods of
cyanosis Cyanosis is the change of body tissue color to a bluish-purple hue as a result of having decreased amounts of oxygen bound to the hemoglobin in the red blood cells of the capillary bed. Body tissues that show cyanosis are usually in locations w ...
. The infant initially attempts to breathe through the nose, and is unable to;
hypercapnia Hypercapnia (from the Greek ''hyper'' = "above" or "too much" and ''kapnos'' = "smoke"), also known as hypercarbia and CO2 retention, is a condition of abnormally elevated carbon dioxide (CO2) levels in the blood. Carbon dioxide is a gaseous pro ...
occurs, and many babies instinctively begin to cry. While crying, oral ventilation occurs and cyanosis subsides. There is variation in the length of time until a baby begins oral breathing, and some will never cease attempts at nasal breathing. It has also been suggested that infants may not be able to sustain oral breathing for significant lengths of time, because of the weakness of the muscles required to seal the nasal airway and open the oral airway. One study employing monitored anatomical occlusion concluded that human infants are not obligate nasal breathers: its sample of nineteen infants, ranging in age from 1 day to 7.5 months, reliably transitioned from nose to mouth breathing after nasal occlusion, providing evidence that infants possess the physiological capability to mouth breathe.


Exercise

Some authors argue that nasal breathing offers a greater advantage over mouth breathing during exercise.


Additional people and activities


George Catlin

George Catlin George Catlin (July 26, 1796 – December 23, 1872) was an American adventurer, lawyer, painter, author, and traveler, who specialized in portraits of Native Americans in the Old West. Traveling to the American West five times during the 1830 ...
was a 19th-century American painter, author, and traveler, who specialized in portraits of Native Americans in the
Old West The American frontier, also known as the Old West or the Wild West, encompasses the geography, history, folklore, and culture associated with the forward wave of American expansion in mainland North America that began with European colonial ...
. Travelling to the
American West The Western United States (also called the American West, the Far West, and the West) is the region comprising the westernmost states of the United States. As American settlement in the U.S. expanded westward, the meaning of the term ''the We ...
five times during the 1830s, he wrote about the life of the
Plains Indians Plains Indians or Indigenous peoples of the Great Plains and Canadian Prairies are the Native American tribes and First Nation band governments who have historically lived on the Interior Plains (the Great Plains and Canadian Prairies) of ...
, and painted portraits that depicted them. He was also the author of several books, including ''The Breath of Life'' (later retitled as ''Shut Your Mouth and Save Your Life'') in 1862. It was based on his experiences traveling through the West, where he observed a consistent lifestyle habit among the Native American communities he encountered: a preference for nose breathing over
mouth breathing Mouth breathing, medically known as chronic oral ventilation, is long-term breathing through the mouth. It often is caused by an obstruction to breathing through the nose, the innate breathing organ in the human body. Chronic mouth breathing ma ...
. He also observed that they had perfectly straight teeth. He repeatedly heard that this was because they believed that mouth breathing made an individual weak and caused disease, while nasal breathing made the body strong and prevented disease. He also observed that mothers repeatedly closed the mouth of their infants while they were sleeping, to instill nasal breathing as a habit.


Yoga

Yogis such as B. K. S. Iyengar advocate both inhaling and exhaling through the nose in the practice of
yoga Yoga (; sa, योग, lit=yoke' or 'union ) is a group of physical, mental, and spiritual practices or disciplines which originated in ancient India and aim to control (yoke) and still the mind, recognizing a detached witness-conscio ...
, rather than inhaling through the nose and exhaling through the mouth. They tell their students that the "nose is for breathing, the mouth is for eating."


See also

*
Aerophagia Aerophagia (or aerophagy) is a condition of excessive air swallowing, which goes to the stomach instead of the lungs. Aerophagia may also refer to an unusual condition where the primary symptom is excessive flatus (farting), belching (burping) i ...
* Breath-holding spell *
Hiccup A hiccup (scientific name ''singultus'', from a Latin word meaning "to catch one's breath while sobbing"; also spelled hiccough) is an involuntary contraction ( myoclonic jerk) of the diaphragm that may repeat several times per minute. The hi ...


References


Further reading

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External links


Effects of Mouth Breathing (and role of nasal breathing)
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WebMD WebMD is an American corporation known primarily as an online publisher of news and information pertaining to human health and well-being. The site includes information pertaining to drugs. It is one of the top healthcare websites. It was f ...
(video clip) {{DEFAULTSORT:Obligate Nasal Breathing Nose Orthodontics Respiration Respiratory physiology Respiratory system