Every day, over seven thousand liters of air pass through our lungs, consisting mainly of nitrogen (78.08%) and oxygen (20.8%), the total concentration of the remaining four gases: carbon dioxide, argon, neon and helium is just over one percent. Despite the fact that the inhaled air contains almost four times less oxygen than nitrogen, the main purpose of breathing is to provide the body with oxygen. Oxygen is needed to oxidize the nutrients that enter the body — proteins, fats and carbohydrates, providing energy release. Also, the breathing process is necessary to remove carbon dioxide from the body, which is formed during the oxidation of substances. The percentage of nitrogen in exhaled air (compared to inhaled air) practically does not change, the oxygen content decreases from 20.8% to 16%, and the carbon dioxide content increases from 0.03% to 4%. In addition, the exhaled air contains water vapor, so with rapid breathing, for example, during intense physical exertion, dehydration develops quickly.

• A person can adapt to the reduced oxygen content in the air, but if the concentration drops below 13%, irreversible changes quickly begin in the cells.;
• The oxygen content in the air of 30% or higher threatens the development of oxygen poisoning associated with the formation of aggressive free radical oxygen species that damage tissues and lead to cell death.;
• Every minute we inhale a volume of oxygen approximately equal to a glass (250 ml), and over 300 liters of this gas are “pumped” through the lungs per day — and this is only in a calm state. With intense physical exertion, oxygen demand can increase to 2.5 liters per minute.
• If there is no ventilation in a room with a volume of six cubic meters, oxygen will be enough for 12 hours of restful stay, with active physical activity – for three to five hours. Further stay in such a room becomes impossible not because of oxygen deficiency, but due to an excess of carbon dioxide up to 2.5% and above, leading to acidification of the body’s environment and depression of the respiratory center.

The breathing process is divided into two stages: external and tissue respiration. External breathing, in turn, includes several stages:

1. Air enters the lungs through the respiratory tract: nasopharynx, trachea, bronchi and alveoli — in which gas exchange occurs. Human alveoli, on average, can hold about six liters of air, including 800-900 ml of oxygen. If all the oxygen contained in the alveoli enters the bloodstream, it will be possible not to breathe for four minutes. However, normal breathing usually leaves an unused reserve in case of sudden oxygen deficiency.
2. Pulmonary gas exchange in the alveolar sacs, which have a very thin wall surrounded by tiny vessels called capillaries. Here, oxygen from the air entering the lungs during inhalation enters the blood, and carbon dioxide, brought to the lungs with the flow of venous blood, enters the alveoli.;
3. Oxygen from the blood is “captured” by red blood cells and binds to the protein hemoglobin — only in this “bound” form can it be absorbed by cells. 4-4.5 liters of blood (the average volume in humans) can “bind” from 750 to 900 ml of oxygen, but usually three to five percent of the protein remains free.
4. Oxygenated blood rushes from the lungs to the heart and, due to its contractions, is “pushed” into blood vessels and capillaries, which directly bring blood to the cells of the body. Oxygen penetrates through the capillary wall and the cell membrane into the cell, where the process of tissue respiration takes place.

Tissue or cellular respiration refers to the processes of oxidation of carbohydrates, fatty acids and amino acids in cells, resulting in the formation of carbon dioxide and water. This releases energy, which is stored in the form of ATP molecules. The resulting carbon dioxide is released from the cell, bound by hemoglobin, and delivered to the alveoli of the lungs, where it enters the alveoli and is removed from the lungs during exhalation.

The respiratory center is a cluster of cells (mainly in the medulla oblongata) responsible for generating and maintaining the rhythm of breathing, its depth and frequency. First of all, its neurons react to the content of carbon dioxide, oxygen in the blood, and fluctuations in the acid-base balance (pH environment). The respiratory center is also affected by signals from various areas of the brain, for example, from the cortical centers responsible for speech and singing; from the hypothalamus, under the influence of hypothalamic impulses, the respiratory rate changes with emotional outbursts, pain; from receptors located in muscles, vascular walls, etc. Sneezing and coughing are the respiratory center’s response to irritation of receptors in the respiratory tract due to ingestion of dust, irritants, and foreign bodies. Thus, the respiratory center helps to adapt breathing to the changing needs of the body during physical exertion, conversation, emotional experiences, changes in body temperature, oxygen and carbon dioxide concentrations in the inhaled air, etc. The breathing process can be regulated consciously, however, when our “arbitrariness” leads to certain chemical disorders, the unconscious mechanisms “intercept” control — a reflexive deep breath occurs.

Several muscle groups are involved in inhaling and exhaling, which are divided into main (diaphragm, external and internal intercostal muscles) and auxiliary (abdominal muscles, neck and shoulder girdle muscles, large and small pectoral muscles). When inhaling, impulses from the neurons of the respiratory center are directed to the diaphragm, leading to its flattening, and to the intercostal muscles, forcing them to “lift” the ribs. The volume of the chest increases, the lungs expand, the pressure in them becomes lower than atmospheric — the air flow rushes here. If you need to take a deeper breath, the pectoral muscles, neck muscles and shoulder girdle are “connected”. When exhaling, the dome of the diaphragm “returns” to the chest, reducing its volume, the lungs contract, the pressure in them increases — the air rushes out. This is a mechanism of calm “passive” exhalation. If you need to force an exhalation, the internal pectoral muscles and abdominal muscles are “connected” — they help to force the air out. In terms of longitude, inspiration correlates with exhalation in a ratio of 1:1.3 (for an adult in a calm state), there is a gap between inhalation and exhalation called an inspiratory pause — it occurs at the height of inspiration. Many breathing practices are based on holding your breath at this exact moment. The combination of inhalation, pause, and exhalation is called the respiratory cycle. Its total duration can range from three to seven seconds. On average, an adult at rest experiences 15 respiratory cycles per minute lasting three to four seconds each. At the same time, the frequency of cycles, as well as the ratio of the duration of inhalation and exhalation, may vary. So, during speech, the duration of exhalation increases significantly and can exceed the length of inspiration by five or more times, and the number of respiratory cycles is 8-10 per minute.

Depending on which muscles are involved in the act of breathing, there are four types of breathing.:

1. The clavicular (upper thoracic) is provided mainly by the muscles of the shoulder girdle, which require a lot of energy and tire quickly. Only the upper parts of the lungs are involved, so the body receives a minimum amount of oxygen. This ineffective type of breathing is observed in a state of anxiety, when you want to “pull your head into your shoulders.” If it becomes basic, stagnation develops in the lungs, the risk of developing bronchitis, pneumonia, etc. increases.
2. Rib (thoracic) breathing is provided by expanding the chest to the sides when inhaling and lowering the ribs when exhaling. It is more effective than the clavicular, however, due to the fact that mainly the middle sections of the lungs are involved, stagnation gradually develops in the lower ones.
3. Abdominal (diaphragmatic) breathing is provided by the contraction and relaxation of the diaphragm, while the volume of the chest increases not from the sides, but from top to bottom. Breathing mainly involves the lower parts of the lungs, which contain maximum oxygen, and the vibrations of the diaphragm “massage” the spleen, liver and adjacent intestines, improving their blood supply. However, the middle and upper parts of the lungs are almost not involved.
4. Chest-abdominal (mixed) breathing involves both the diaphragm and pectoral muscles, as a result of which all parts of the lungs are involved, therefore it is considered the most effective. Mixed breathing prevails in children, and in adulthood it develops as a result of conscious efforts (for example, by singers, speakers, and also during the development of many breathing practices).

Proper breathing is a necessary condition for maintaining health, preventing many diseases, maintaining a balance of energy and a stable emotional state. What kind of breathing is considered correct?

1. Nasal breathing.  It is in the nasal cavity that the air is cleaned of dust and mechanical impurities — they are trapped by the cilia covering the mucous membrane. The nasal passages also contain mucus rich in immunoglobulin A, immune cells — this is the first protective barrier against dangerous microbes. In addition, the air that has passed through the nasal passages does not irritate the lungs, as it warms and humidifies in the nasal cavity. When we breathe through our mouths, this does not happen. We can train ourselves to breathe through our nose consciously: having acquired this habit, we soon begin to breathe through our nose without thinking, even during sleep.
2. Mixed breathing. To master it, you need to exhale and wait for the moment when you want to inhale. Then slowly inhale through your nose. At first, there is a feeling that the air “enters the stomach” — at the same time, it inflates slightly. Next, the volume of the chest increases; at the very end, the shoulders rise, and the stomach begins to retract. On exhaling, the abdomen continues to retract, then the chest falls off, and the shoulders drop. Before the next breath, it is important to pause, since with abdominal breathing, significantly more oxygen enters the bloodstream than with other types, so dizziness may develop from unaccustomed breathing.
3. Breathing exercises. In order to master the technique of mixed breathing, it is advisable to master each type of breathing separately, and breathing exercises aimed at training each type will help. Abdominal breathing: lie on your back, bend your knees, and place your palms on your navel. During the breathing process, the palms should go down and up with the stomach. Chest breathing: sit up straight, place your palms on the area of the lower ribs under the chest, make sure that the chest expands and falls during breathing. Clavicular breathing: in a sitting position, place the palms of your hands on your chest parallel to the sternum, with the tips of your fingers in the collarbone area. Make sure that the collarbones fall and fall when breathing.
4. Breathing practices, yoga. Regulating breathing is an important part of most health and mindfulness practices. So, in yoga, many breathing exercises are associated with holding your breath: it is believed that short-term stress caused by oxygen deficiency has a beneficial effect on the functioning of the brain and vital organs. However, it is necessary for a beginner to do this kind of exercise in the presence of an experienced instructor. It is important that breathing practices increase awareness: a person begins to be aware of how and when he breathes and how this affects his condition.
5. Clean air: even the most correct breathing will not benefit if the air we breathe contains dust, excess carbon dioxide, tobacco smoke and other harmful impurities. That is why it is so important to ventilate the premises regularly, do wet cleaning, avoid active and passive smoking, and try to do without aggressive household chemicals. It is also important that there are no copiers in living rooms, especially in the bedroom or kitchen, as their cartridges emit microparticles that quickly penetrate the lungs. The bonuses that help improve air quality are live plants, as well as special installations for purifying and humidifying the air.

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