Obligate nasal breathing

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.


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.[1] 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.[2]


According to Jason Turowski, MD of the Cleveland Clinic, "we are designed to breathe through our noses from birth — it’s the way humans have evolved."[3] 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.[4][5] In addition, nasal breathing produces nitric oxide within the body while mouth breathing does not.[6][4][7][8] Mouth breathing also leads to having a dry mouth, throat infections, a reduced sense of taste,[5] and other chronic conditions.[7][9][10][11][12] Nasal breathing is a research interest in Orthodontics (and the related field of Myofunctional Therapy)[13] and for biological anthropologists.[14]


Human infants are commonly described as obligate nasal breathers as they breathe through their nose rather than the mouth.[15] Most infants, however, are able to breathe through their mouth if their nose is blocked.[15] There are however certain infants with conditions such as choanal atresia in which deaths have resulted from nasal obstruction.[15] In these cases there are cyclical periods of cyanosis. The infant initially attempts to breathe through the nose, and is unable to; hypercapnia 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.[15]


Studies indicate that nasal breathing offers a greater advantage over mouth breathing during exercise.[8][16]

Covid-19 studiesEdit

As of April 2020, studies and trials are underway that examine the possible benefits of nitric oxide in the treatment of Covid-19.[17][6][18][19] This research is based on the fact that nitric oxide was investigated as an experimental therapy for SARS.[20] Brian Strickland, MD, a fellow in Wilderness Medicine at Massachusetts General Hospital who studies “acute respiratory distress” in high altitudes, is applying this research towards Covid-19.[21][22] He is currently involved in clinical trials which apply the use of inhaled nitric oxide as a treatment for Covid-19.[23] This approach was inspired by the work of Associate Professor of Emergency Medicine at the Harvard Medical School N. Stuart Harris, who has been studying the effects of altitude sickness on mountain climbers, such as those who climb Mount Everest. Harris noticed that the consequences of high level altitude sickness on the human body mirrored Covid -19’s dysfunctional impact on the lungs. His focus on nitric oxide comes from its role in being able to breathe in high altitudes.[21][24] According to WCVB-TV, similar trials are being conducted at Tufts Medical Center.[25] Other studies speculate that replacing mouth breathing (which decimates NO) with nasal breathing (which increases NO)[4][7][8] is a “lifestyle change” that “may also help to reduce SARS-CoV-2 viral load and symptoms of COVID-19 pneumonia by promoting more efficient antiviral defense mechanisms in the respiratory tract.”[9]

Additional people and activitiesEdit

George CatlinEdit

George Catlin was a 19th century American painter, author, and traveler, who specialized in portraits of Native Americans in the Old West. Travelling to the American West five times during the 1830s, he wrote about, and painted portraits that depicted, the life of the Plains Indians.[26] He was also the author of several books, including The Breath of Life[27](later retitled as Shut Your Mouth and Save Your Life) in 1862..[28][29] 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. He also observed that they had perfectly straight teeth.[30] 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.[30] He also observed that mothers repeatedly closed the mouth of their infants while they were sleeping, in order to instill nasal breathing as a habit.[31] He thus wrote the book to document these observations, stating that "there is no person in society but who will find... improvement in health and enjoyment..." from keeping his or her mouth shut.[32]


Yogis such as B. K. S. Iyengar advocate both inhaling and exhaling through the nose in the practice of yoga, rather than inhaling through the nose and exhaling through the mouth.[33][34][35] They tell their students that the "nose is for breathing, the mouth is for eating."[34][36][37][33]


Horses are also considered obligate nasal breathers. The term is more accurate in horses, because their normal anatomy prevents them from breathing orally. The epiglottis 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 results in dorsal displacement of the soft palate (DDSP),[38] and it has been suggested that this leads to a clinical syndrome which may include oral breathing.[39] However, significant respiratory dysfunction including airway obstruction is observed with DDSP, and the animal cannot function normally in this state.

Rabbits 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.[40] Even so, rabbits with advanced upper airway disease will attempt to breathe through their mouths.

Many other mammals, such as cats, dogs, and adult humans, have the ability to breathe indefinitely through either the oral or nasal cavity.[41]

See alsoEdit

Further readingEdit

  • Nestor, James (2020). Breath: The New Science of a Lost Art. Riverhead Books. ISBN 978-0735213616.


  1. ^ SIDS and Otitis media – an anatomical perspective, Presented by: Brian Palmer, D.D.S., December 2001.
  2. ^ Negus, VE (1927). "The Function of the Epiglottis". Journal of Anatomy. 62 (Pt 1): 1–8. PMC 1250045. PMID 17104162.
  3. ^ Turowski, Jason (2016-04-29). "Should You Breathe Through Your Mouth or Your Nose?". Cleveland Clinic. Retrieved 2020-06-28.
  4. ^ a b c Glazier, M.D., Eve (2019-11-04). "'Nose breathing has more benefits than mouth breathing". The Times and Democrat. Retrieved 2020-07-09.
  5. ^ a b "Your Nose, the Guardian of Your Lungs". Boston Medical Center. Retrieved 2020-06-29.
  6. ^ a b Cohan, Alexi (2020-07-26). "Nitric oxide, a 'miracle molecule,' could treat or even prevent coronavirus, top doctors say". Boston Herald. Retrieved 2020-07-27.
  7. ^ a b c Dahl, Melissa (2011-01-11). "'Mouth-breathing' gross, harmful to your health". NBC News. Retrieved 2020-06-28.
  8. ^ a b c Berman, Joe (2019-01-29). "Could nasal breathing improve athletic performance?". Washington Post. Retrieved 2020-05-31.
  9. ^ a b Martel, Jan; Ko, Yun-Fei; Young, John D.; Ojcius, David (2020-05-06). "Could nasal nitric oxide help to mitigate the severity of COVID-19?". Microbes and Infection. doi:10.1016/j.micinf.2020.05.002. Retrieved 2020-05-06.
  10. ^ Rao A, ed. (2012). Principles and Practice of Pedodontics (3rd ed.). New Delhi: Jaypee Brothers Medical Pub. pp. 169, 170. ISBN 9789350258910.
  11. ^ Nall, Rachel (September 22, 2017). "What's wrong with breathing through the mouth?". Medical News Today. Retrieved 2020-05-31.
  12. ^ Valcheva, Zornitsa (January 2018). "THE ROLE OF MOUTH BREATHING ON DENTITION DEVELOPMENT AND FORMATION" (PDF). Journal of IMAB. Retrieved 2020-05-31.
  14. ^ Gross, Terry (2020-05-27). "How The 'Lost Art' Of Breathing Can Impact Sleep And Resilience". National Public Radio (NPR)/Fresh Air. Retrieved 2020-06-23.
  15. ^ a b c d Bergeson, P. S.; Shaw, J. C. (2001). "Are Infants Really Obligatory Nasal Breathers?". Clinical Pediatrics. 40 (10): 567–9. doi:10.1177/000992280104001006. PMID 11681824.
  16. ^ Flanell, Michael (2019-06-06). "The Athlete's Secret Ingredient: The Power of Nasal Breathing" (PDF). EC Pulmonology and Respiratory Medicine. 8 (6): 471–475. Retrieved 2020-05-08.
  17. ^ Katsnelson, Alla (2020-05-20). "Multiple clinical trials test whether NO gas can treat and prevent COVID-19". Chemical & Engineering News. Retrieved 2020-07-14.
  18. ^ Gander, Kashmira (2020-04-07). "What Is Nitric Oxide? How the Gas That Gave Us Viagra Could Help Treat Coronavirus Patients". Newsweek. Retrieved 2020-06-25.
  19. ^ "Nitric Oxide Investigated as COVID-19 Treatment". WebMD. Retrieved 10 April 2020.
  20. ^ Åkerström, Sara; Mousavi-Jazi, Mehrdad; Klingström, Jonas; Leijon, Mikael; Lundkvist, Åke; Mirazimi, Ali (1 February 2005). "Nitric Oxide Inhibits the Replication Cycle of Severe Acute Respiratory Syndrome Coronavirus". Journal of Virology. 79 (3): 1966–1969. doi:10.1128/JVI.79.3.1966-1969.2005. PMC 544093. PMID 15650225.
  21. ^ a b Powell, Alvin (2020-05-06). "Applying wisdom from the Himalayas to the ER's COVID battle". The Harvard Gazette. Retrieved 2020-06-25.
  22. ^ "Lessons from the Backcountry in Finding a Potential COVID-19 Treatment". Massachusetts General Hospital. 2020-06-24. Retrieved 2020-06-25.
  23. ^ "Inhaled Nitric Oxide Therapy for Emergency Room COVID-19 Patients". Massachusetts General Hospital. 2020-06-24. Retrieved 2020-06-25.
  24. ^ Meredith, Sam (2020-05-01). "How the gas that gave the world Viagra could help treat coronavirus patients". CNBC. Retrieved 2020-07-05.
  25. ^ Riemer, Emily (2020-06-23). "Tufts researchers test inhaled nitric oxide as COVID-19 treatment". WCVB-TV. Retrieved 2020-07-05.
  26. ^ "Catlin Virtual Exhibition". Smithsonian American Art Museum. Archived from the original on 25 September 2014. Retrieved 28 October 2014.
  27. ^ "The breath of life, or mal-respiration,and its effects upon the enjoyments & life of man". HathiTrust. Retrieved 2020-06-28.
  28. ^ "George Catlin on Mouth Breathing". PubMed. Retrieved 2020-07-02.
  29. ^ Nestor, James (2020). Breath: The New Science of a Lost Art. Riverhead Books. p. 48. ISBN 978-0735213616.
  30. ^ a b Nestor, James (2020). Breath: The New Science of a Lost Art. Riverhead Books. p. 49. ISBN 978-0735213616.
  31. ^ Nestor, James (2020). Breath: The New Science of a Lost Art. Riverhead Books. p. 50. ISBN 978-0735213616.
  32. ^ p. 86, Catlin, George: Keep Your Mouth Shut, eighth edition, 1882, Trubner & Co., London
  33. ^ a b Yoga Journal Editors (2017-04-12). "Q&A: Is Mouth Breathing OK in Yoga?". Yoga Journal. Retrieved 2020-06-26.
  34. ^ a b Payne, Larry. "Yogic Breathing: Tips for Breathing through Your Nose (Most of the Time)". Yoga For Dummies, 3rd Edition. Retrieved 2020-06-26.
  35. ^ Himalayan Institute Core Faculty, Himalayan Institute Core Faculty (2017-07-13). "Yogic Breathing: A Study Guide". Himalayan Institute of Yoga Science and Philosophy. Retrieved 2020-06-26.
  36. ^ Krucoff, Carol (2013). "Yoga Sparks". New Harbinger Publications. Retrieved 2020-05-31.
  37. ^ Jurek, Scott (2012). "Eat and Run". Houghton Mifflin. Retrieved 2020-05-31.
  38. ^ Holcombe, SJ; Derksen, FJ; Stick, JA; Robinson, NE (1998). "Effect of bilateral blockade of the pharyngeal branch of the vagus nerve on soft palate function in horses". American journal of veterinary research. 59 (4): 504–8. PMID 9563638.
  39. ^ Susan J. Holcombe (1998). "Neuromuscular Regulation of the Larynx and Nasopharynx in the Horse" (PDF). Proceedings of the Annual Convention of the AAEP. 44: 26.
  40. ^ Stephen J. Hernandez-Divers (2007). "The Rabbit Respiratory System: Anatomy, Physiology, and Pathology" (PDF). Proceedings of the Association of Exotic Mammal Veterinarians: 61–68.
  41. ^ Radostits, Otto M.; Mayhew, I. G. Joe; Houston, Doreen M., eds. (2000). Veterinary clinical examination and diagnosis. Philadelphia: W. B. Saunders. ISBN 0-7020-2476-7.[page needed]

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