Types of breathing age-related changes. Age features of the respiratory system in newborns and children

Fetal respiration. In intrauterine life, the fetus receives 0 2 and removes CO 2 exclusively through the placental circulation. However, the large thickness of the placental membrane (10-15 times thicker than the pulmonary membrane) does not allow equalizing the partial stresses of gases on both sides of it. The fetus develops rhythmic respiratory movements a frequency of 38-70 per minute. These breathing movements are reduced to a slight expansion chest, which is replaced by a longer decline and an even longer pause. At the same time, the lungs do not straighten out, remain collapsed, the alveoli and bronchi are filled with fluid, which is secreted by alveolocytes. In the interpleural fissure, only a slight negative pressure arises as a result of the discharge of the outer (parietal) pleura and an increase in its volume. The respiratory movements of the fetus occur with a closed glottis, and therefore amniotic fluid does not enter the respiratory tract.

The significance of the fetal respiratory movements: 1) they increase the speed of blood flow through the vessels and its flow to the heart, and this improves the blood supply to the fetus; 2) the respiratory movements of the fetus contribute to the development of the lungs and respiratory muscles, i.e. those structures that the body will need after its birth.

Features of transport of gases by blood. The oxygen tension (P0 2) in the oxygenated blood of the umbilical vein is low (30-50 mm Hg), the content of oxyhemoglobin (65-80%) and oxygen (10-150 ml / l of blood) is reduced, and therefore it is still less in the vessels of the heart, brain and other organs. However, fetal hemoglobin (HbF), which has a high affinity for 0 2 , functions in the fetus, which improves the supply of oxygen to cells due to the dissociation of oxyhemoglobin at more low values partial pressure of gas in tissues. By the end of pregnancy, the content of HbF decreases to 40%. Voltage carbon dioxide(PC0 2) in arterial blood fetus (35-45 mm Hg. Art.) low due to hyperventilation of pregnant women. The enzyme carbonic anhydrase is absent in erythrocytes, as a result of which up to 42% of carbon dioxide, which can combine with bicarbonates, is excluded from transport and gas exchange. Most of the physical dissolved CO 2 is transported through the placental membrane. By the end of pregnancy, the content of CO 2 in the blood of the fetus increases to 600 ml / l. Despite these features of gas transport, fetal tissues have an adequate supply of oxygen due to the following factors: tissue blood flow is approximately 2 times greater than in adults; anaerobic oxidative processes prevail over aerobic ones; energy costs of the fetus are minimal.

Breath of a newborn. From the moment the baby is born, even before the clamping of the umbilical cord, pulmonary breathing begins. The lungs fully expand after the first 2-3 respiratory movements.

The reasons for the first breath are:

• 1) excess accumulation CO 2 and H + and depletion of 0 2 blood after the cessation of placental circulation, which stimulates the central chemoreceptors;
• 2) a change in the conditions of existence, a particularly powerful factor is the irritation of skin receptors (mechano- and thermoceptors) and increasing afferent impulses from vestibular, muscle and tendon receptors;
• 3) the pressure difference in the interpleural gap and in the airways, which at the first breath can reach 70 mm of water column (10-15 times more than during subsequent quiet breathing).

In addition, as a result of irritation of the receptors located in the nostrils, the amniotic fluid (diver's reflex) stops inhibition respiratory center. Excitation of the inspiratory muscles (diaphragm) occurs, which causes an increase in volume chest cavity and decreased intrapleural pressure. The inspiratory volume is greater than the expiratory volume, which leads to the formation of an alveolar air reserve (functional residual capacity). Exhalation in the first days of life is carried out actively with the participation of the expiratory muscles (expiratory muscles).

Significant elasticity is overcome during the first breath lung tissue due to the surface tension of collapsed alveoli. During the first breath, energy is expended 10-15 times more than in subsequent breaths. To stretch the lungs of not yet breathing children, the pressure air flow should be about 3 times greater than in children who switched to spontaneous breathing.

Facilitates the first breath superficially active substance- surfactant, which in the form of a thin film covers the inner surface of the alveoli. The surfactant reduces surface tension forces and the work required for ventilation of the lungs, and also maintains the alveoli in a straightened state, preventing them from sticking together. This substance begins to be synthesized on the 6th month of intrauterine life. When the alveoli are filled with air, it spreads over the surface of the alveoli with a monomolecular layer. Non-viable newborns who died from alveolar adhesions were found to lack surfactant.

The pressure in the interpleural fissure of the newborn during exhalation is atmospheric pressure, decreases during inhalation and becomes negative (in adults, it is negative both during inhalation and exhalation).

According to the generalized data, in newborns the number of respiratory movements per minute is 40-60, the minute breathing volume is 600-700 ml, which is 170-200 ml / min / kg.

With the onset of pulmonary respiration due to the expansion of the lungs, the acceleration of blood flow and the reduction of the vascular bed in the system pulmonary circulation blood circulation through the small circle changes. An open arterial (botallian) duct in the first days, and sometimes weeks, can maintain hypoxia by directing part of the blood from pulmonary artery into the aorta, bypassing the lesser circle.

Features of frequency, depth, rhythm and type of breathing in children. Breathing in children is frequent and shallow. This is due to the fact that the work spent on breathing, in comparison with adults, is greater, since, firstly, diaphragmatic breathing, since the edges are horizontal, perpendicular spinal column which limits chest excursion. This type of breathing remains the leading one in children up to 3-7 years of age. It requires overcoming the resistance of the organs abdominal cavity(Children have a relatively large liver and frequent swelling intestines); secondly, in children, the elasticity of the lung tissue is high (low extensibility of the lungs due to the small number of elastic fibers) and significant bronchial resistance due to the narrowness of the upper respiratory tract. In addition, the alveoli are smaller, poorly differentiated, and limited in number (air/tissue surface area is only 3 m2 versus 75 m2 in adults).

Respiratory frequency in children of different ages is presented in Table. 6.1.

Respiratory rate in children of different ages

Table 6.1

The respiratory rate in children changes significantly during the day, and also significantly more than in adults, it changes under the influence of various influences (mental arousal, physical activity, increased body temperature and environment). This is due to the mild excitability of the respiratory center in children.

Up to 8 years, the respiratory rate in boys is slightly higher than in girls. By puberty, the respiratory rate in girls becomes greater, and this ratio is maintained for life.

Breathing rhythm. In newborns and infants breathing irregular. Deep breathing is replaced by shallow. Pauses between inhalation and exhalation are uneven. The duration of inhalation and exhalation in children is shorter than in adults: inhalation is 0.5-0.6 s (in adults 0.98-2.82 s), and exhalation is 0.7-1 s (in adults 1.62 -5.75 s). Already from the moment of birth, the same ratio between inhalation and exhalation is established as in adults: inhalation is shorter than exhalation.

Breath types. In a newborn, until the second half of the first year of life, the diaphragmatic type of breathing predominates, mainly due to the contraction of the muscles of the diaphragm. Thoracic breathing is difficult, as the chest is pyramidal, the upper ribs, the handle of the sternum, the collarbone and the entire shoulder girdle are high, the ribs lie almost horizontally, and the respiratory muscles of the chest are weak. From the moment when the child begins to walk and increasingly takes vertical position, breathing becomes chest-abdominal. From 3-7 years old due to the development of the muscles of the shoulder girdle chest type breathing begins to prevail over the diaphragmatic. Sexual differences in the type of breathing begin to be revealed from the age of 7-8 and end by the age of 14-17. By this time, the chest type of breathing is formed in the girls, and the abdominal type of breathing in the boys.

Lung volumes in children. In a newborn child, lung volume increases slightly during inspiration. The tidal volume is only 15-20 ml. During this period, the body is provided with O, due to an increase in the frequency of respiration. With age, along with a decrease in the respiratory rate, the tidal volume increases (Table 6.2). Minute respiratory volume (MOD) also increases with age (Table 6.3), amounting to 630-650 ml / min in newborns, and 6100-6200 ml / min in adults. At the same time, the relative volume of respiration (the ratio of MOD to body weight) in children is approximately 2 times greater than in adults (in newborns, the relative volume of respiration is about 192, in adults - 96 ml / min / kg). This is due to the high level of metabolism and consumption of 0 2 in children compared with adults. So, the need for oxygen is (in ml / min / kg of body weight): in newborns - 8-8.5; at 1-2 years old - 7.5-8.5; at 6-7 years old - 8-8.5; at 10-11 years old -6.2-6.4; at 13-15 years old - 5.2-5.5 and in adults - 4.5.

Vital lung capacity in children different ages(V.A. Doskin et al., 1997)

Table 6.2

The vital capacity of the lungs is determined in children from the age of 4-5, since the active and conscious participation of the child himself is required (Table 6.2). In a newborn, the so-called vital capacity of a cry is determined. It is believed that with a strong cry, the volume of exhaled air is equal to VC. In the first minutes after birth, it is 56-110 ml.

Age indicators of minute volume of breathing (V.A. Doskin et al., 1997)

Table 6.3

Increase absolute indicators of all respiratory volumes is associated with the development of the lungs in ontogenesis, an increase in the number and volume of alveoli up to 7-8 years of age, a decrease in aerodynamic resistance to breathing due to an increase in the lumen of the respiratory tract, a decrease in elastic resistance to breathing due to an increase in the proportion of elastic fibers in the lungs relative to collagen ones, an increase in strength respiratory muscles. Therefore, the energy cost of breathing is reduced (Table 6.3).

The meaning of breathing. Structure and functions respiratory system.

Age features respiratory system.

1. The meaning of breathing. The structure and functions of the respiratory system

The respiratory system consists of the following organs: nasal cavity, nasopharynx, larynx, trachea, bronchi and lungs.

The main function of the respiratory system is associated with the intake of oxygen into the body and the release of carbon dioxide. Respiration is the process of providing the cells of the body with oxygen necessary for the oxidative processes of energy metabolism, which are the essence of tissue respiration. The respiratory system itself provides the so-called external respiration and gas exchange between the lungs and blood, which occurs in the alveoli of the lungs. Blood acts as a transport system for gases.

In addition to the described function, the respiratory system is associated with:

the function of protecting the body from the ingress of dust and microorganisms (mucus secreted by goblet cells of the ciliated epithelium and the ciliated epithelium of the respiratory tract itself, relieving us of protective mucus along with dust and microorganisms);

protective reflexes of sneezing and coughing;

function of approaching the temperature of the inhaled air to the temperature internal environment body (abundant blood supply to the mucous membrane of the upper respiratory tract);

function of humidification of the inhaled air;

the function of removing metabolic products (carbon dioxide, water vapor, etc.);

function of distinguishing odors (olfactory receptors).

I would especially like to note the importance of nasal breathing. When breathing through the nose, the cells of a special neuroepithelium associated with the brain are irritated. Irritation of these cells contributes to the development of the child's brain (therefore nasal breathing is so important for children and such obstacles as polyps and adenoids need to be removed), affects our performance, mood, and behavior. To be convinced of this, it is enough to remember your feelings during a runny nose. For symmetrical stimulation of the neuroepithelium of the right and left half of the nasal cavity, it is also necessary to avoid curvature of the nasal septum, which easily occurs in children due to mechanical trauma to the nose.

2. Age features of the respiratory system

The mucous membranes of the respiratory tract in children are thin, tender, dry (little mucus is secreted), richly supplied with blood, and contain many lymphatic vessels. They are easily injured, the protective function is less pronounced than in adults. Therefore, children often develop inflammation of the respiratory tract, which makes nasal breathing difficult. This is accompanied by oxygen starvation, because. oxygenation of the blood begins already in the nasal cavity. Breathing through the mouth creates even more favorable conditions for infection to enter the body. The most common route of infection transmission in children's groups is airborne. In children's institutions, it is especially important to monitor the sanitary and hygienic condition of the premises (wet cleaning, ventilation, air purity), as well as to monitor compliance with the regulations for the daily mandatory stay of children in the fresh air.

The upper respiratory tract in children is narrower than in adults, and if they are also closed by adenoids, polyps, excess mucus when inflammatory processes, then the child's body suffers from a lack of oxygen (especially the brain), the pronunciation of sounds is disturbed, and perhaps even a violation of mental development (see above the functions of the neuroepithelium of the nasal cavity). An adenoid type of face is formed - an open mouth, puffiness and a dull facial expression.

The lungs of a child are abundantly supplied with lymphatic vessels, which makes frequent inflammatory processes possible. Lung development ends by age 7, followed by lung growth.

The functionality of the lungs is largely determined by the shape of the chest. Until about 6 years of age, it has a cone-shaped shape with an almost horizontal arrangement of ribs, which makes it difficult to ventilate the lungs. Breathing is superficial. The small volume of the chest, and, consequently, the lungs also does not contribute to gas exchange. However, intensive growth requires sufficient oxygen supply to the cells. This is possible due to the high blood flow velocity and respiratory rate.

The shape of the chest changes by about 6 years. It becomes barrel-shaped with an oblique arrangement of ribs, which significantly affects the ventilation of the lungs and reduces the frequency of respiratory movements.

The frequency of respiratory movements decreases with age: in newborns - 30-44 breaths. movement in minutes; at 5 years - 26 breaths. movement in minutes; in adolescents - 18 breaths. movement in minutes; in young men - 16 breaths. movement in min. Breathing becomes deeper with age.

For proper development respiratory system requires exercise, sports. At the same time, respiratory muscles develop, voluntary and involuntary regulation of breathing is trained, correct posture is formed, and functionality respiratory system, and, therefore, the oxygenation of cells and tissues, the metabolism in them. All this has a beneficial effect on the growth and development of the child's body.

Age features of the respiratory system

Newborn nasal cavity low and narrow. The superior nasal passage is absent. By 6 months life, the height of the nasal cavity increases. By the age of 10 - 1.5 times, and by the age of 20 - 2 times.

Nasopharynx the newborn is relatively wide, and Eustachian tube short, and therefore diseases of the upper respiratory tract in children are often complicated by inflammation of the middle ear, since the infection easily penetrates into the middle ear through a wide and short Eustachian tube.

Larynx in newborns it is located higher than in adults, as a result of which the child can simultaneously breathe and swallow. The cartilages of the larynx, thin in newborns, become thicker with age. After 2–3 years, the larynx in girls lags behind in growth, it becomes shorter and smaller than in boys, which persists in adults. Sex differences in the larynx are most noticeable in the thyroid cartilage and vocal cords. At the age of 12–14, in boys, at the junction of the plates of the thyroid cartilage, the Adam's apple begins to grow, the vocal cords, the entire larynx becomes wider and longer than in girls. In boys, during this period, there is a breaking of the voice.

Tracheal growth in children is carried out in accordance with the growth of the body. By the age of 10, its length increases by 2 times, by the age of 25 - by 3 times. The mucous membrane of the trachea and nasopharynx of children is tender and rich in blood vessels.

Bronchi in children they are narrow, the mucous membrane contains few mucous glands, richly supplied with blood vessels. Bronchial growth is most vigorous in the first year of life and during puberty.

lung growth carried out due to the branching of small bronchi, the formation of alveoli and an increase in their volume. Up to 3 years of age increased growth lungs and differentiation of their individual elements. Between the ages of 3 and 7 years, the growth rate of the lungs decreases. Alveoli grow especially vigorously after 12 years. Lung capacity increases at this age

10 times compared with the lung capacity of a newborn, and by the end of puberty - 20 times.

Rib cage the child grows parallel to the growth of the body, the ribs take an inclined downward position and begin to take part in breathing. The type of breathing becomes mixed. The reflex regulation of respiration is improved, i.e. the cerebral cortex gradually begins to control the activity of the respiratory center of the medulla oblongata, however, the morphological and functional immaturity of the respiratory organs persists up to 14 years. The formation of sex differences in the structure of the chest and the type of breathing ends by the age of 21. However, the development of the respiratory organs and the improvement of its regulation continues in adults. At the same time, there are significant individual differences depending on whether a person is engaged in physical labor, sports or leads sedentary image life, smokes, drinks alcohol.

Breathing movements. First breath the newborn occurs as a result of a sharp excitation of the center of inspiration after cutting the umbilical cord. In newborns, the muscles of the ribs do not participate in breathing, and it is carried out only due to contractions of the diaphragm (diaphragmatic or abdominal type of breathing). The breathing of a newborn is superficial and frequent (up to 60 per minute), ventilation in the peripheral areas of the lungs is poorly expressed, the minute volume of the lungs is only 1300 ml (in an adult 4–6 l).

In children of the first year of life, the frequency of respiratory movements is 50–60 per minute during wakefulness. In children 1-2 years old - 35-40 per minute; at

2-4 year olds - 25-35 per minute and 4-6 year olds - 23-26 per minute. Schoolchildren

there is a decrease in the respiratory rate to 18-20 per minute.

important for the growth and development of the child nasal breathing, the shutdown of which leads to sleep and digestion disorders and, as a result, to a lag in physical and mental development. Careful care of the nasal cavity of infants is required, and in the event of diseases of the nasopharynx (rhinitis, nasopharyngitis, nasal adenoids), appropriate treatment should be carried out immediately.

At the age of 3 to 7 years, in connection with the development of the shoulder girdle, more and more begins to predominate chest type of breathing. During puberty, the chest takes on the shape of an adult, although it remains even smaller in size. The chest in girls takes on a cylindrical shape, and the type of breathing becomes thoracic (the upper ribs are more actively involved in breathing than the lower ones). In boys, it takes on a conical shape with the base facing upwards (the shoulder girdle is wider than the pelvis) and type of breathing becomes abdominal(lower ribs and diaphragm are actively involved in breathing). At this age, the rhythm of breathing increases, the respiratory rate decreases to 20 per minute, and the depth increases, and the minute volume of the lungs is 3500-4000 ml, which is close to that of an adult. By the age of 18, the respiratory rate is set at 16-17 per minute, and the minute volume of breathing corresponds to

adult norm.

Literature

a) basic literature

1. Sapin M.P., Sivoglazov V.I. Human anatomy and physiology (with age-related features child's body): Proc. allowance. M., 1997.

2. Bezrukikh M.M., Sonkin V.D., Farber D.A. Age physiology: (Physiology of child development): Proc. allowance. M., 2002.

3. Lyubimova, Z.V. Age physiology: textbook. for university students: at 2h. Part 1 / Z. V. Lyubimova, K. V. Marinova, A. A. Nikitina. - M.: Vlados, 2004, 2008. - 301 p. - Recommended by the Ministry of Defense of the Russian Federation.

b) additional literature

1. Obreimova, N.I. Fundamentals of anatomy, physiology and hygiene of children and adolescents: Proc. allowance / N.I. Obreimova, A.S. Petrukhin - M.: Academy, 2008. - 368 p.

2. Aleshina, L.I. Methodological guide to laboratory studies in age-related anatomy, physiology and human hygiene / L.I. Aleshina, S.Yu. Lebedchenko, M.V. Muzhichenko, E.I. Novikova, S.A. Suleimanova, M.M. Tobolskaya, N.A. Fedorkina, E.A. Shulgin. - Volgograd.: Change, 2005. - 141 p.

In children, the mucous membranes of the upper respiratory tract and vocal cords are very delicate and easily vulnerable, so they often suffer from a runny nose, inflammation of the larynx, bronchi and lungs. Proper breathing through the nose plays an important role in the prevention of respiratory and vocal apparatus diseases. During nasal breathing, air, before entering the larynx, bronchi and lungs, passes through narrow, winding nasal passages, where it is cleaned of dust, microbes and other harmful impurities, moistened and warmed. This does not happen when breathing through the mouth. In addition, when breathing through the mouth, it is difficult normal rhythm and the depth of breathing and the passage of air into the lungs per unit time decreases. Breathing through the mouth in children most often occurs when chronic runny nose, the appearance of adenoids in the nasopharynx. Nasal obstruction adversely affects general condition child: he turns pale, becomes lethargic, gets tired easily, sleeps poorly, suffers from headaches, physical and mental development its slowing down. Such a child should be urgently shown to the doctor. If the reason is not correct breathing are adenoids, they are removed. After this simple and harmless operation, the child's condition improves significantly, physical and mental development quickly returns to normal. With inflammation of the larynx (laryngitis), the vocal cords located on the inner surface lateral walls of the larynx. Laryngitis has two forms: acute and chronic. Acute laryngitis is accompanied by cough, sore throat, pain when swallowing, talking, hoarseness, sometimes even loss of voice (aphonia). If they are not received in a timely manner necessary measures treatment, acute laryngitis can go to chronic form. To protect the respiratory organs and vocal apparatus from diseases in children great importance has no sharp fluctuations

air and food temperatures. Do not take children out of very hot rooms or after hot bath(baths) in the cold, allowed to drink cold drinks or eat ice cream in a hot state. Strong tension of the vocal apparatus can also lead to inflammation of the larynx. It is necessary to ensure that children do not talk loudly for a long time, do not sing, do not shout or cry, especially in damp, cold and dusty rooms or on walks in adverse weather. Learning poems and singing (with the observance of the voice mode and breathing) contribute to the development and strengthening of the larynx, vocal cords and lungs. So that the vocal cords do not overstrain, recite poetry in a calm, quiet voice, sing without tension; the continuity of the sound should not exceed 4-5 minutes. Children, due to the peculiarities of their respiratory apparatus, cannot significantly change the depth of breathing during physical exertion, but increase their breathing. Already frequent and shallow breathing in children during physical exertion it becomes even more frequent and superficial. This results in lower ventilation efficiency, especially in young children. Teaching children to breathe correctly when walking, running and other activities is one of the tasks of the teacher. One of the conditions for proper breathing is taking care of the development of the chest. For this, the correct position of the body is important. Especially while sitting at a desk, breathing exercises and other physical exercises that develop the muscles that move the chest. Especially useful in this regard are sports such as swimming, rowing, skating, skiing. Usually a person with a well-developed chest will breathe evenly and correctly. It is necessary to teach children to walk and stand in a straight posture, as this contributes to the expansion of the chest, facilitates the activity of the lungs and ensures deeper breathing. When the body is bent, less air enters the body.

In this part we are talking about changing external respiration with age: about changing the type of breathing, about changing the rhythm and frequency of breathing with age, about changing with age the value of respiratory and minute volumes lungs, their vital capacity.

Changes in external respiration with age.

Changing the type of breathing.

Diaphragmatic breathing persists until the second half of the first year of life. As the child grows, the chest descends and the ribs take on an oblique position. At the same time, mixed breathing (chest-abdominal) occurs in infants, and stronger mobility of the chest is observed in its lower sections. In connection with the development of the shoulder girdle (3-7 years), chest breathing begins to predominate. By the age of 7, breathing becomes predominantly chest.

From the age of 8-10, there are gender differences in the type of breathing: in boys, a predominantly diaphragmatic type of breathing is established, and in girls - chest.

Changes in the rhythm and frequency of breathing with age.

In newborns and infants, breathing is irregular. Arrhythmia is expressed in the fact that deep breathing is replaced by shallow breathing, pauses between inhalations and exhalations are uneven. The duration of inhalation and exhalation in children is shorter than in adults: inhalation is 0.5-0.6 sec (in adults - 0.98-2.82 sec), exhalation - 0.7-1 sec (in adults - from 1.62 to 5.75 sec). Some researchers believe that in newborns in the first days of life, inhalation is 25% longer than exhalation. Most support the opinion that from the moment of birth, the same ratio between inhalation and exhalation is established as in adults: inhalation is shorter than exhalation.

The frequency of respiratory movements in children decreases with age. In the fetus, it ranges from 46-64 per minute. A gradual decrease occurs by the age of 14-15, when the respiratory rate approaches its value in an adult.

Due to the mild excitability of the respiratory center, the respiratory rate fluctuates not only within one age group, but also in one subject during the day.

The breathing of newborns and infants in the waking state is very uneven, it is more calm during sleep.

Up to 8 years, the respiratory rate in boys is greater than in girls. By puberty, the respiratory rate in girls becomes greater, and this ratio is maintained throughout life.

The respiratory rate in children is much greater than in adults, it changes under the influence of various influences. It increases with mental excitations, small physical exercises, a slight increase in body temperature and the environment.

Change with age in the respiratory and minute volumes of the lungs, their vital capacity.

The vital capacity of the lungs, respiratory and minute volumes in children gradually increase with age due to the growth and development of the chest and lungs.

In a newborn child, the lungs have little elasticity and are relatively large. During inspiration or volume increases slightly, only 10-15 mm. Providing the child's body with oxygen occurs by increasing the frequency of breathing. The tidal volume of the lungs increases with age, along with a decrease in the respiratory rate.

Change in lung volume with age.

The relative volume of breathing (the ratio of respiratory volume to body weight) in children is greater than in adults; in newborns, it exceeds the value of adults by 2 times. So, in adults, the ratio of the respiratory volume of air to body weight is 6, and in newborns it is about 12. This is due to the high metabolism in children and, consequently, the high need of a growing organism for oxygen. Very varied data are given on the value of minute volume, depending on the method of measurement. With age, the value of the minute volume of the lungs increases. But the relative minute volume of the lungs (the ratio of minute volume of breath to body weight) decreases with age. In newborns and children of the first year of life, it is twice as large as in adults. This is due to the fact that in children with the same relative tidal volume, the respiratory rate is several times greater than in adults. In this regard, pulmonary ventilation per 1 kg of body weight in children is greater. The value of pulmonary ventilation per 1 kg of body weight in newborns is 400 ml, at 5-6 years of age it is 210, at 7 years of age - 160, at 8-10 years of age - 150, at 11-13 years of age - 130-145 , 14-year-olds - 125, and 15-17-year-olds - 110. This ensures a large need for a growing organism in O 2.

The value of the vital capacity of the lungs increases with age due to the growth of the chest and lungs. In a child of 5-6 years old, it is 700-800 ml, at 14-16 years old it is 2500-2600 ml. From 18 to 25 years old vital capacity lung is maximum, and after 35-40 years decreases. The value of the vital capacity of the lungs varies depending on age, height, type of breathing, gender (girls are 100-200 ml less than boys).

The vital capacity of the lungs is more or less constant, with fluctuations not exceeding 100 ml. It largely depends on the physical development and training of children. The highest value was noted in skiers, rowers, swimmers, runners (up to 6000 ml). The increase in the vital capacity of the lungs occurs due to the growth of the alveoli.

The respiratory surface of the lungs and the amount of blood flowing through the lungs per unit time are relatively larger in children than in adults. Due to the large development of capillaries in the lungs of a child, the surface of contact between blood and alveolar air in children is also relatively larger than in adults. All this contributes to better gas exchange in the lungs of a growing organism, which is necessary to ensure intensive metabolism.

In children, breathing changes in a peculiar way during physical work. During exercise, the frequency of respiratory movements increases and the respiratory volume of the lungs almost does not change. Such breathing is not economical and cannot ensure long-term performance of work.

Pulmonary ventilation in children when performing physical work increases by 2-7 times, and with heavy loads(mid-distance running) almost 20 times.

The maximum oxygen consumption in an adult at rest is 150-300 ml per minute. In children, it is much less and increases with work. When performing physical work in trained children 10-13 years old, the maximum oxygen consumption is 49 ml per 1 kg of body weight per minute, for untrained children - 47.3 ml. The increase in oxygen consumption during work in children from 9 to 18 years old occurs in the same way and after 3 minutes it becomes maximum: in the first minute it reaches 45% of the maximum value, in the second it increases to 75%, and in the third it reaches a maximum.

The dependence of the value of maximum oxygen consumption on training in children is less pronounced than in adults. In adolescents, the maximum in oxygen consumption is reached faster, but since they cannot (like adults) keep their oxygen consumption at the maximum level for a long time, they stop working faster.

At the end of the work in the recovery period, the repayment of the "oxygen debt" in children occurs faster. Restoration is carried out already during operation. In girls and boys aged 14-18, oxygen consumption and carbon dioxide release during recovery period slightly more than in adults. Recovery from junior schoolchildren 8-12 years old when running 50 meters is faster than for older students, and when running 100 meters faster for older ones - 12-16-year-olds.

With age, the ability to recover during work decreases, and oxygen debt increases. The value of oxygen debt per 1 kg of weight in older children is greater than in children younger age.

The absolute value of oxygen consumption in boys of 8-9 years is 2 times less than in boys of 16-18 years. In girls, when performing maximum work, oxygen consumption is less than in boys, especially at 8-9 years old and at 16-18. All this should be taken into account when doing physical labor and sports with children of different ages.

The lungs and airways begin to develop in the 3rd week embryo from the mesodermal mesenchyme. In the future, in the process of growth, the lobar structure of the lungs is formed, after 6 months alveoli are formed. At 6 months, the surface of the alveoli begins to be covered with a protein-lipid lining - surfactant. Its presence is necessary condition normal aeration of the lungs after birth. With a lack of surfactant, after air enters the lungs, the alveoli collapse, which leads to severe disorders breathing without treatment.

The lungs of the fetus as an organ of external respiration do not function. But they are not in a dormant state, the alveoli and bronchi of the fetus are filled with fluid. In the fetus, starting from the 11th week, there are periodic contractions of the inspiratory muscles - the diaphragm and intercostal muscles.

At the end of pregnancy, the respiratory movements of the fetus occupy 30-70% of the total time. The frequency of respiratory movements usually increases at night and in the morning, as well as with an increase in the motor activity of the mother. Breathing movements are necessary for normal development lungs. After they are turned off, the development of the alveoli and the increase in lung mass slows down. In addition, the respiratory movements of the fetus represent a kind of preparation of the respiratory system for breathing after birth.

Birth calls drastic changes the state of the respiratory center located in medulla oblongata leading to ventilation. The first breath occurs, as a rule, after 15-70 seconds. after birth.

The main conditions for the occurrence of the first breath are:

1. Increases in the blood of humoral irritants of the respiratory center, CO 2 , H + and lack of O 2;

2. A sharp increase in the flow of sensitive impulses from skin receptors (cold, tactile), proprioreceptors, vestibuloreceptors. These impulses activate the reticular formation of the brainstem, which increases the excitability of the neurons of the respiratory center;

3. Elimination of sources of inhibition of the respiratory center. Irritation of the receptors located in the nostrils with liquid greatly inhibits breathing (diver's reflex). Therefore, immediately after the appearance of the head of the fetus, obstetricians remove mucus and amniotic fluid from the face.

Thus, the occurrence of the first breath is the result of the simultaneous action of a number of factors.

The beginning of lung ventilation is associated with the beginning of the functioning of the pulmonary circulation. The blood flow through the pulmonary capillaries sharply increases. The lung fluid is absorbed from the lungs into the bloodstream, part of the fluid is absorbed into the lymph.

In young children, calm breathing is diaphragmatic. This is due to the structural features of the chest. The ribs are located at a large angle to the spine, so the contraction of the intercostal muscles is less effective in changing the volume of the chest cavity. The energy cost of a child's breath is much higher than that of an adult. The reason is the narrow airways and their high aerodynamic resistance, as well as the low extensibility of the lung tissue.

Another distinctive feature is more intensive ventilation of the lungs in terms of kilogram of body weight in order to satisfy high level oxidative processes and lower permeability of the pulmonary alveoli for O 2 and CO 2. So, in newborns, the respiratory rate is 44 cycles per minute, the tidal volume is 16 ml, and the minute respiratory volume is 720 ml / min. In children of 5-8 years of age, the respiratory rate decreases and reaches 25-22 cycles per minute, the tidal volume is 160-240 ml, and the minute respiratory volume is 3900-5350 ml / min. In adolescents, the respiratory rate ranges from 18 to 17 cycles per minute, tidal volume - from 330 to 450 ml, minute breathing volume - from 6000 to 7700 ml / min. These values ​​are closest to the level of an adult.

With age, the vital capacity of the lungs, the permeability of the pulmonary alveoli for O 2 and CO 2 increase. This is due to an increase in body weight and working muscles, with an increase in the need for energy resources. In addition, breathing becomes more economical, as evidenced by a decrease in respiratory rate and tidal volume.

The greatest morphological and functional changes in the lungs cover the age period up to 7-8 years. At this age, there is an intense differentiation bronchial tree and an increase in the number of alveoli. The growth of lung volumes is also associated with a change in the diameter of the alveoli. In the period from 7 to 12 years, the diameter of the alveoli doubles, by adulthood - three times. The total surface of the alveoli increases 20 times.

Thus, the development respiratory function lung occurs unevenly. The most intensive development is noted at the age of 6-8, 10-13, 15-16 years. In these age periods the growth and expansion of the tracheobronchial tree predominates. In addition, at this time, the process of differentiation of the lung tissue proceeds most intensively, which is completed by 8-12 years. Critical periods for the development of the functional capabilities of the respiratory system are observed at the age of 9-10 and 12-13 years.

The stages of maturation of the regulatory functions of the lungs are divided into three periods: 13-14 years (chemoreceptor), 15-16 years (mechanoreceptor), 17 years and older (central). A close relationship was noted between the formation of the respiratory system and physical development and maturation of other body systems.

Intensive development skeletal muscles at the age of 12-16 affects the nature of the age-related transformations of the respiratory system of a teenager. In particular, in adolescents with high growth rates, there is often a lag in the development of the respiratory organs. Outwardly, this manifests itself in the form of shortness of breath, even when performing small physical activity. These children complain fatigue, have low muscle performance, avoid activities with intense exercise. For them it is recommended gradual increase classes physical education under the supervision of a doctor.

In contrast, in adolescents involved in sports, the annual increase in growth is less, and the functionality of the lungs is higher. But in general, the development of the respiratory organs in the vast majority of children bears the "imprints of civilization." Low physical activity restricts chest movement. Breathing in this case is superficial, and its physiological value is low. Children need to be taught how to deep breathing, which is a necessary condition for maintaining health, expanding the possibility of adapting to physical activity.