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Why breathing should be strictly nasal
When seeing people on Western city streets and in other public places, one may notice that up to 20-40% of them breathe through their mouths while walking or even while quietly standing or sitting. This phenomenon is even more common among children. What are the known negative effects of mouth breathing?
Reduced oxygenation and carbon dioxide stores
Scientific literature on respiration often mentions a physiological parameter known as dead space volume. It is about 150-200 ml in an average adult: inside the throat, nose and bronchi. This space preserves additional carbon dioxide for the organism, since inhalations take CO2 enriched air from dead space back into the lungs. When the mouth is open, the dead space volume becomes smaller due to a continuous exchange of air. That does not happen with nasal breathing. In addition, nasal breathing provides more resistance to respiratory muscles during breathing as compared to mouth breathing (the mouth-breathing route is shorter and has a larger cross sectional area). During nasal breathing we can either breathe more resulting in more mechanical work for the respiratory muscles or breathe slightly less while generating less mechanical work. What is the practical result? Due to an in-built tendency to optimize physiological processes, the human organism is more likely, as during nose-breathing, to breathe less and tolerate higher aCO2, than to exert more demands on constantly working respiratory muscles.
In the abstract of a physiological study "An assessment of nasal functions in control of breathing" (Tanaka et al, 1988) the Japanese researchers wrote:
"Breathing pattern and steady-state CO2 ventilatory response during mouth breathing were compared with those during nose breathing in nine healthy adults...We found the following. 1) Dead space and airway resistance were significantly greater during nose than during mouth breathing. ...These results fit our observation that end-tidal PCO2 was significantly higher during nose than during mouth breathing. It is suggested that a loss of nasal functions, such as during nasal obstruction, may result in lowering of CO2, fostering apneic spells during sleep."
This article, which studied a group of healthy volunteers, gives average end-tidal CO2 43.7 mm Hg for nasal breathing and only 40.6 mm Hg for mouth breathing. Practically, in terms of CP (Control Pause) that means 45 s and 37 s at sea level. Hence, mouth breathing reduces oxygenation of the whole body.
"Autoinhalation of nasal NO (nitric oxide, the hormone that is naturally produced in nasal passages of humans) increases oxygenation and reduces pulmonary artery pressure in humans." This was the conclusion of Swedish doctors and researchers from Department of Anaesthesiology and Intensive Care of the Karolinska Hospital in Stockholm. This study was published in European Respiratory Journal (2002 May; 19(5): p.859-864. Törnberg DC, Marteus H, Schedin U, Alving K, Lundberg JO, Weitzberg E, Nasal and oral contribution to inhaled and exhaled nitric oxide: a study in tracheotomized patients). Learn more about nitric oxide effects below.
Cleaning, warming and humidification of air in case of nasal breathing
Our nasal passages are created to clean, humidify and warm the incoming flow of air due to the thin layer of protective mucus. This layer of mucus can trap almost all (97-99%) dust particles, bacteria, viruses and other airborne objects. This is what long, narrow, and intricate nasal airways are for.
When the mouth is used for inhalation, this air route is shorter, wider and almost straight. Now the same airborne objects can easily get into the alveoli and the blood, creating stress, first of all, for the immune system (detection, marking, isolation, and deactivation of intruders) and then for organs of elimination (kidneys, liver, skin, and GI patches). Some pathogens can even multiply in the lungs causing more severe problems.
If you are an asthmatic and an endurance athlete, you should train mostly, or even better, only using your nose. For really important competitions mouth-breathing can be used if you have no problems with your asthma. What is important for training is to have an aerobic training effect. That is possible while breathing through the nose, as these western results indicate.
“The major cause of exercise-induced asthma (EIA) is thought to be the drying and cooling of the airways during the 'conditioning' of the inspired air. Nasal breathing increases the respiratory system's ability to warm and humidify the inspired air compared to oral breathing and reduces the drying and cooling effects of the increased ventilation during exercise. This will reduce the severity of EIA provoked by a given intensity and duration of exercise. The purpose of the study was to determine the exercise intensity (%VO2 max) at which healthy subjects, free from respiratory disease, could perform while breathing through the nose-only and to compare this with mouth-only and mouth plus nose breathing. Twenty subjects (11 males and 9 females) ranging from 18-55 years acted as subjects in this study. They were all non-smokers and non-asthmatic. At the time of the study, all subjects were involved in regular physical activity and were classified, by a physician, as free from nasal polyps or other nasal obstruction. The percentage decrease in maximal ventilation with nose-only breathing compared to mouth and mouth plus nose breathing was three times the percentage decrease in maximal oxygen consumption. The pattern of nose-only breathing at maximal work showed a small reduction in tidal volume and large reduction in breathing frequency. Nasal breathing resulted in a reduction in FEO2 and an increase in FECO2. While breathing through the nose-only, all subjects could attain a work intensity great enough to produce an aerobic training effect (based on heart rate and percentage of VO2 max)” (abstract, Morton et al, 1995).
As noted by Andrey Novozshilov, the chief physician of the Buteyko Clinic in Moscow,
"Medical professionals are well aware that the mouth-breathing child is soon going to slow down in mental and physiological development in relation to schoolmates. Mouth breathing, in general, from physiological viewpoint, is unacceptable. What happens when we breathe through the nose? On the mucosal surface of the nose microbes and viruses die; air is cleaned, warmed to optimum temperature, humidified till the optimum level and, in this ready form, enters bronchi." Interview with Dr. Andrey Novozshilov; published in the Russian national magazine “Krasota i zdorov'e” (Beauty and health), 2003
A group of American doctors from the Department of Surgery of the University of Chicago even wrote an article with the title "Observations on the ability of the nose to warm and humidify inspired air" (Naclerio RM, Pinto J, Assanasen P, Baroody FM, published in Rhinology 2007 Jun; 45(2): p.102-111.) The abstract of the study suggests,
"The major function of the nose is to warm and humidify air before it reaches to the lungs for gas exchange. Conditioning of inspired air is achieved through evaporation of water from the epithelial surface. The continuous need to condition air leads to a hyperosmolar environment on the surface of the epithelium. As ventilation increases, the hyperosmolar surface moves more distally, covering a larger surface area of the airway, and stimulates epithelial cells to release mediators that lead to inflammation. This inflammation is not identical to allergic inflammation, but causes both short-term and long-term changes in the epithelium. In the short-term, it increases paracellular water transport in an attempt to enhance conditioning, and it stimulates sensory nerves to initiate neural reflexes. It also disrupts channels in the cellular membrane, which might permit greater penetration of foreign proteins, such as allergens, leading to further inflammatory cascades. The long-term inflammation induced over time by the hyperosmolar milieu could worsen the ability of the nose to condition air, requiring more of the conditioning to occur in the lower airway and leading to adverse consequences for the respiratory system."
Autoimmunization effect for nasal breathing
The layer of mucus moves as a carpet from sinuses, bronchi and other surfaces towards the stomach. Hence, these trapped by the mucus objects are drained (or swallowed) into the stomach where digestive enzymes and HCl (low pH) make bacteria and viruses either dead or weak. Further along the digestive conveyor, some of these substances can penetrate into the blood due to intestinal permeability effect. But now these pathogens are either dead or weakened and would not do much harm while providing a good lesson for the immune system. This is exactly how immunization, done by medical personnel, often works with success: medical doctors inject a vaccine with either dead or weakened bacteria or virus to teach and strengthen the immune response to these pathogens. Hence, nasal breathing is a natural mechanism of autoimmunization.
Practically, when some household members are sick with for example, the flu or a cold, the still healthy people can breathe either through the nose, teaching their own immune system how to defeat the pathogenic bacteria or virus, or through the mouth, allowing the same pathogens to access, settle and multiply in various parts of the human body causing the infection.
Utilization of own nitric oxide generated in nasal airways
Normal nasal breathing helps the body to use its own nitric oxide. This substance is produced in, among other places, nasal passages. During normal breathing, we have quiet prolonged exhalations (that do not prevent accumulation of nitric oxide in some areas of nasal passages) and relatively quick inhalations (that allow inhalation of the accumulated nitric oxide). During hyperventilation, exhalations are forceful and quick (as one can observe in many sick people) and inhalations are slow. This reversal of the main stages of breathing decreases the utilization of nitric oxide.
The roles, and some important effects, of this hormone on the body have been discovered very recently (in the last 2 decades) and there are still many questions in relation to this substance. Nitric oxide is found and synthesized in endothelial cells that line the lumen of blood vessels, neurons, and macrophages. As a gas, it is routinely found in nasal passages and measured in exhaled air. The known functions of the NO include:
1.Vasodilation of arteries and arterioles (and hence regulation of blood flow to tissues). In this respect, NO is similar to CO2 acting on the smooth muscles of blood vessels.
2. Regulation of binding and release of O2 to hemoglobin. This NO function is again similar to the CO2 function known as the Bohr effect.
3.Destruction of parasitic organisms, viruses, and malignant cells by inactivating their respiratory chain enzymes in mitochondria.
4. Inhibition of inflammation in blood vessels.
5.Neurotransmission. Learning, memory, sleeping, feeling pain, and some other processes require NO for transmission of neuronal signals. On the other hand, brain cells can probably be killed during a stroke due to excessive production of nitric oxide.
6.Hormonal effects. NO influences secretion from several endocrine glands. It stimulates the release of adrenaline from the adrenal medulla, pancreatic enzymes from the exocrine portion of pancreas, and Gonadotropin-releasing hormone from the hypothalamus.
Abnormal NO production and its availability are now associated with hypertension, heart failure, stroke, obesity, diabetes (both type I and II), atherosclerosis, rheumatism, aging, and dyslipidemias (particularly hypercholesterolemia and hypertriglyceridemia).
Heart patients, who often breathe through the mouth, may notice that their heart problems have a tendency to appear when do so. Apart from all CO2-related effects, they do not normally utilize own NO (nitric oxide) generated in the nasal passages. During the First World War it was noticed that people who worked with explosives had abnormally low blood pressure. Later, the chemical became one of the popular pills to reduce blood pressure, nitro-glycerine. The main effect of this chemical is to produce NO. Hence, if these patients close their mouth, their medication needs can be reduced.
Obviously, during mouth breathing it is not possible to utilize one's own nitric oxide that is synthesized in the sinuses.
The mouth, according to Doctor Buteyko, is designed by Nature for drinking, eating and speaking. At all other times it should be shut. (Teeth flossing and brushing can be other sensible exceptions.)
Read more abstracts about nasal nitric oxide here.
Nasal breathing 24/7 (even during night sleep and exercise)
For many sick people quick health improvement (the initial stage of breathing normalization) is accomplished by one change only: learning how to breathe through the nose 24/7. Just this step alone can make a big difference in health of many people so that the main symptoms are reduced and less medication is required.
Dr. Buteyko, while studying respiration during physical activity, observed that breathing through the nose made a big difference in the after-effects of physical exercise. Moreover, physical activity with oral breathing often led to lower CPs and CO2 later, whereas nasal breathing during walking and other physical activities was beneficial.
Most medical doctors do not know when and how sick people should exercise. It is known that exercise can be useful, but sick people often die or experience heart attacks, exercise-induced asthma attacks, and other exacerbations or acute states of their diseases during or after physical exercise. However, when physical exercise is done with strictly nasal breathing (in and out), physical activity is 100% safe even for severely sick people. (They would not be able to have intensive exercise and will rely on lighter activities, like walking. We are going to learn more about rules and types of beneficial exercise later.)
Since many patients and sick people open their mouth and breathe through the mouth at night, in the 1960s Dr. Buteyko patients invented a technique (mouth taping) that will be described in the learning section of this website.
If a person has blocked nose, there is also a breathing exercise "How to unblock the nose", which is explained later.
For more abstracts about other benefits of nasal breathing (Mouth breathing and morning fatigue; Nasal breathing, sleep apnea, and snoring; Mouth breathing in asthmatics; etc.) click here.
Devastating effects of mouth breathing on health of children (medical abstracts), which do not require any further comments.
For the list of the quoted references click here
(Excerpts from the book "Normal breathing: the key to vital health")