Features of lung tissue in young children. Anatomical and physiological features of the respiratory system in children

The formation of the respiratory system in a child begins at 3-4 weeks of intrauterine existence. By the 6th week of embryonic development, the child develops branching of the respiratory organs of the second order. At the same time, the formation of the lungs begins. By the 12th week of the intrauterine period, areas of lung tissue appear in the fetus. Anatomical and physiological features - AFO of the respiratory organs in children undergo changes as the baby grows. The correct development of the nervous system, which is involved in the process of breathing, is of decisive importance..

upper respiratory tract

In newborn babies, the bones of the skull are not sufficiently developed, due to which the nasal passages and the entire nasopharynx are small and narrow. The mucous membrane of the nasopharynx is tender and permeated with blood vessels. She is more vulnerable than an adult. Nasal appendages are most often absent, they begin to develop only by 3-4 years.

As the baby grows, the nasopharynx also increases in size. By the age of 8, the baby has a lower nasal passage. In children, the paranasal sinuses are located differently than in adults, due to which the infection can quickly spread into the cranial cavity.

In children, a strong proliferation of lymphoid tissue is observed in the nasopharynx. It reaches its peak by the age of 4, and from the age of 14 it begins to reverse development. Tonsils are a kind of filters, protecting the body from the penetration of microbes. But if the child is often sick for a long time, then the lymphoid tissue itself becomes a source of infection.

Children often suffer from respiratory diseases, which is due to the structure of the respiratory organs and insufficient development of immunity.

Larynx

In small children, the larynx is narrow, funnel-shaped. Only later does it become cylindrical. The cartilage is soft, the glottis is narrowed, and the vocal cords themselves are short. By the age of 12 boys have longer vocal cords than girls. This is the reason for the change in the timbre of the voice of the boys.

Trachea

The structure of the trachea also differs in children. During the first year of life, it is narrow, funnel-shaped. By the age of 15, the upper part of the trachea reaches the 4th cervical vertebra. By this time, the length of the trachea also doubles, it is 7 cm. In children, it is very soft, therefore, with inflammation of the nasopharynx, it is often compressed, which is manifested by stenosis.

Bronchi

The right bronchus is, as it were, a continuation of the trachea, and the left bronchus moves away at an angle. That is why, if foreign objects accidentally enter the nasopharynx, they often end up in the right bronchus.

Children are susceptible to bronchitis. Any cold can result in inflammation of the bronchi, a strong cough, high fever and a violation of the general condition of the baby.

Lungs

The lungs of children undergo changes as they grow up. The mass and size of these respiratory organs increase, and differentiation occurs in their structure. In children, there is little elastic tissue in the lungs, but the intermediate tissue is well developed and contains a large number of vessels and capillaries.

The lung tissue is full-blooded, it contains less air than in adults. By the age of 7, the formation of the acinus ends, and until the age of 12, the growth of the formed tissue simply continues. By the age of 15, the alveoli increase by 3 times.

Also, with age, the mass of lung tissue increases in children, more elastic elements appear in it. Compared with the neonatal period, the mass of the respiratory organ increases by the age of 7 by approximately 8 times.

The amount of blood that flows through the capillaries of the lungs is higher than in adults, which improves gas exchange in the lung tissue.

Rib cage

The formation of the chest in children occurs as they grow and ends only closer to 18 years. According to the age of the child, the volume of the chest increases.

In infants, the sternum is cylindrical in shape, while in adults, the rib cage becomes oval. In children, the ribs are also located in a special way, due to their structure, the child can painlessly switch from diaphragmatic to chest breathing.

Features of breathing in a child

In children, the respiratory rate is increased, while the respiratory movements are the more frequent, the smaller the child. From the age of 8, boys breathe more often than girls, but starting from adolescence, girls begin to breathe more often and this state of affairs persists throughout the entire time.

To assess the condition of the lungs in children, it is necessary to consider the following parameters:

• The total volume of respiratory movements.
• The volume of air inhaled per minute.
• Vital capacity of the respiratory organs.

The depth of breathing in children increases as they grow older. The relative volume of breathing in children is twice as high as in adults. Vital capacity increases after physical exertion or sports exercises. The more physical activity, the more noticeable the change in the nature of breathing.

In a calm state, the child uses only part of the vital capacity of the lungs.

Vital capacity increases as the diameter of the chest grows. The amount of air that the lungs can ventilate in one minute is called the respiratory limit. This value also increases as the child grows.

Of great importance for the assessment of pulmonary function is gas exchange. The content of carbon dioxide in the exhaled air of schoolchildren is 3.7%, while in adults this value is 4.1%.

Methods for studying the respiratory system of children

To assess the condition of the respiratory organs of the child, the doctor collects an anamnesis. The medical card of a small patient is carefully studied, and complaints are clarified. Next, the doctor examines the patient, listens to the lower respiratory tract with a stethoscope and taps them with his fingers, paying attention to the type of sound made. Then the examination takes place according to the following algorithm:

• The mother finds out how the pregnancy proceeded, and whether there were any complications during childbirth. In addition, it is important what the baby was sick with shortly before the onset of problems with the respiratory tract.
• They examine the baby, paying attention to the nature of breathing, the type of cough and the presence of discharge from the nose. They look at the color of the skin, their cyanosis indicates oxygen deficiency. An important sign is shortness of breath, its occurrence indicates a number of pathologies.
• The doctor asks the parents if the child has short-term pauses in breathing during sleep. If such a condition is characteristic, then this may indicate problems of a neurological nature.
• An x-ray is prescribed to clarify the diagnosis, if pneumonia and other pathologies of the lungs are suspected. X-rays can be performed even for young children, if there are indications for this procedure. To reduce the level of exposure, it is recommended to conduct examinations of children on digital devices.
• Examination with a bronchoscope. It is carried out with bronchitis and suspicion of a foreign body entering the bronchi. With the help of a bronchoscope, a foreign body is removed from the respiratory organs.
• Computed tomography is performed when cancer is suspected. This method, although expensive, is the most accurate.

In young children, bronchoscopy is performed under general anesthesia. This excludes injuries to the respiratory organs during the examination.

The anatomical and physiological features of the respiratory system in children differ from those of adults. The respiratory organs in children continue to grow until about 18 years of age. Their size, vital capacity and weight increase.

Oxygen reserves in the body are very limited, and they are enough for 5-6 minutes. Providing the body with oxygen is carried out in the process of respiration. Depending on the function performed, there are 2 main parts of the lung: conductive part to bring air into and out of the alveoli respiratory part, where gas exchange takes place between air and blood. The conductive part includes the larynx, trachea, bronchi, i.e. the bronchial tree, and the actual respiratory part includes the acini, consisting of the afferent bronchioles, alveolar passages and alveoli. External respiration refers to the exchange of gases between atmospheric air and the blood of the capillaries of the lungs. It is carried out by simple diffusion of gases through the alveolar-capillary membrane due to the difference in oxygen pressure in the inhaled (atmospheric) air and venous blood flowing through the pulmonary artery into the lungs from the right ventricle (Table 2).

table 2

Partial pressure of gases in inhaled and alveolar air, arterial and venous blood (mm Hg)

Index	Inhaled air	Alveolar air	arterial blood	Deoxygenated blood
RO 2
RSO 2
RN 2
RN 2 ABOUT
General pressure

The difference in oxygen pressure in the alveolar air and venous blood flowing through the pulmonary capillaries is 50 mm Hg. Art. This ensures the passage of oxygen into the blood through the alveolar-capillary membrane. The difference in carbon dioxide pressure causes its transition from venous blood to alveolar air. The efficiency of the function of the external respiration system is determined by three processes: ventilation of the alveolar space, adequate ventilation of the lungs by capillary blood flow (perfusion), diffusion of gases through the alveolar-capillary membrane. Compared with adults, children, especially the first year of life, have pronounced differences in external respiration. This is due to the fact that in the postnatal period there is a further development of the respiratory sections of the lungs (acini), where gas exchange occurs. In addition, children have numerous anastomoses between the bronchial and pulmonary arteries and capillaries, which is one of the reasons for blood shunting, bypassing the alveolar spaces.

Currently, the function of external respiration is evaluated according to the following groups of indicators.

Pulmonary ventilation- frequency (f), depth (Vt), minute volume of breathing (V), rhythm, volume of alveolar ventilation, distribution of inhaled air.

lung volumes- vital capacity (VC, Vc), total lung capacity, inspiratory reserve volume (IRV, IRV), expiratory reserve volume (ERV, ERV), functional residual capacity (FRC), residual volume (VR).

Breath mechanics- maximum lung ventilation (MVL, Vmax), or respiratory limit, respiratory reserve, forced vital capacity (FEV) and its relation to VC (Tiffno index), bronchial resistance, inspiratory and expiratory volumetric velocity during calm and forced breathing.

Pulmonary gas exchange- the value of oxygen consumption and carbon dioxide release in 1 min, the composition of the alveolar air, the oxygen utilization factor.

Gas composition of arterial blood- partial pressure of oxygen (PO 2) and carbon dioxide (PCO 2), the content of oxyhemoglobin in the blood and arteriovenous difference in hemoglobin and oxyhemoglobin.

The depth of breathing, or tidal volume (TO, or Vt, in ml), in children, both in absolute and relative numbers, is much less than in an adult (Table 3).

Table 3

Tidal volume in children depending on age

Age	Tidal volume in children, ml
			According to N. A. Shalkov
	Abs. number	Per 1 kg of body weight	Abs. number	Per 1 kg of body weight
Newborn
adults

This is due to two reasons. One of them, of course, is the small mass of the lungs in children, which increases with age, and during the first 5 years, mainly due to the neoplasm of the alveoli. Another, no less important reason explaining the shallow breathing of young children is the structural features of the chest (anterior-posterior size is approximately equal to the lateral size, the ribs depart from the spine at almost a right angle, which limits the excursion of the chest and changes in lung volume). The latter changes due mainly to the movement of the diaphragm. An increase in tidal volume at rest may indicate respiratory failure, and a decrease in it may indicate a restrictive form of respiratory failure or chest rigidity. At the same time, the need for oxygen in children is much higher than in adults, which depends on a more intensive metabolism. So, in children of the first year of life, the need for oxygen per 1 kg of body weight is approximately 7.5-8 ml/min, by the age of 2 it slightly increases (8.5 ml/min), by the age of 6 it reaches its maximum value (9 .2 ml / min), and then gradually decreases (at 7 years - 7.9 ml / min, 9 years - 6.8 ml / min, 10 years - 6.3 ml / min, 14 years - 5.2 ml /min). In an adult, it is only 4.5 ml / min per 1 kg of body weight. The superficial nature of breathing, its irregularity is compensated by a higher respiratory rate (f). So, in a newborn - 40-60 breaths per 1 min, in a one-year-old - 30-35, in a 5-year-old - 25, in a 10-year-old - 20, in an adult - 16-18 breaths in 1 min. The respiratory rate reflects the body's compensatory capabilities, but in combination with a small tachypnea volume, it indicates respiratory failure. Due to the greater respiratory rate, per 1 kg of body weight, the minute volume of respiration is significantly higher in children, especially at an early age, than in adults. In children under 3 years of age, the minute volume of breathing is almost 1.5 times greater than in an 11-year-old child, and more than 2 times than in an adult (Table 4).

Table 4

Minute respiratory volume in children

Indicators	Novorozh money	3 months	6 months	1 year	3 years	6 years	11 years	14 years	adults
MOD, cm
MOD per 1 kg of body weight

Observations of healthy people and children with pneumonia have shown that at low temperatures (0 ... 5 ° C) there is a decrease in breathing while maintaining its depth, which is, apparently, the most economical and efficient breathing to provide the body with oxygen. It is interesting to note that a warm hygienic bath causes a 2-fold increase in lung ventilation, and this increase occurs mainly due to an increase in the depth of breathing. From here it becomes quite clear the proposal of A. A. Kisel (an outstanding Soviet pediatrician), which he made back in the 20s of the last century and which became widespread in pediatrics, to widely use the treatment of pneumonia with cold fresh air.

Vital capacity of the lungs(VC, Vc), i.e., the amount of air (in milliliters) that is maximally exhaled after maximum inspiration (determined by a spirometer), is significantly lower in children than in adults (Table 5).

Table 5

Vital capacity of the lungs

Age	VC, ml	Volumes, ml
		respiratory	reserve exhalation	reserve breath
4 years
6 years
Adult

If we compare the vital capacity of the lungs with the volume of breathing in a calm position, it turns out that children in a calm position use only about 12.5% ​​of the VC.

Inspiratory reserve volume(RVD, IRV) - the maximum volume of air (in milliliters) that can be additionally inhaled after a quiet breath.

For its assessment, the ratio of ROVD to VC (Vc) is of great importance. In children aged 6 to 15 years, EVR/VC ranges from 55 to 59%. A decrease in this indicator is observed with restrictive (restrictive) lesions, especially with a decrease in the elasticity of the lung tissue.

expiratory reserve volume(ROvyd, ERV) - the maximum volume of air (in milliliters) that can be exhaled after a quiet breath. As with inspiratory reserve volume, ERV (ERV) is measured in relation to VC (Vc). In children aged 6 to 15 years, ER/VC is 24-29% (increases with age).

Vital capacity of the lungs decreases with diffuse lesions of the lungs, accompanied by a decrease in the elastic extensibility of the lung tissue, with an increase in bronchial resistance or a decrease in the respiratory surface.

forced vital capacity(FVC, FEV), or forced expiratory volume (FEV, l / s), is the amount of air that can be exhaled during forced exhalation after a maximum inspiration.

Tiffno index(FEV in percent) - the ratio of FEV to VC (FEV%), normally for 1 s FEV is at least 70% of the actual VC.

Maximum ventilation(MVL, Vmax), or breathing limit, is the maximum amount of air (in milliliters) that can be ventilated in 1 minute. Usually this indicator is examined within 10 s, since signs of hyperventilation (dizziness, vomiting, fainting) may occur. MVL in children is significantly less than in adults (Table 6).

Table 6

Maximum ventilation in children

Age, years	Average data, l/min	Age, years	Average data, l/min

So, in a child of 6 years, the breathing limit is almost 2 times less than in an adult. If the respiratory limit is known, then it is not difficult to calculate the value of the respiratory reserve (the value of the minute volume of respiration is subtracted from the limit). A smaller value of vital capacity and rapid breathing significantly reduce the respiratory reserve (Table 7).

Table 7

Respiratory reserve in children

Age, years	Respiratory reserve, l/min	Age, years	Respiratory reserve, l/min

The effectiveness of external respiration is judged by the difference in the content of oxygen and carbon dioxide in the inhaled and exhaled air. So, this difference in children of the first year of life is only 2-2.5%, while in adults it reaches 4-4.5%. Exhaled air in young children contains less carbon dioxide - 2.5%, in adults - 4%. Thus, young children absorb less oxygen for each breath and emit less carbon dioxide, although gas exchange in children is more significant than in adults (in terms of 1 kg of body weight).

Of great importance in judging the compensatory capabilities of the external respiration system is the oxygen utilization factor (KIO 2) - the amount of oxygen absorbed (PO 2) from 1 liter of ventilated air.

KIO 2 \u003d PO 2 (ml / min) / MOD (l / min).

In children under 5 years old, KIO 2 is 31-33 ml / l, and at the age of 6-15 years - 40 ml / l, in adults - 40 ml / l. KIO 2 depends on the conditions of oxygen diffusion, the volume of alveolar ventilation, on the coordination of pulmonary ventilation and blood circulation in the pulmonary circulation.

The transport of oxygen from the lungs to the tissues is carried out by the blood, mainly in the form of a chemical compound with hemoglobin - oxyhemoglobin, and to a lesser extent - in a dissolved state. One gram of hemoglobin binds 1.34 ml of oxygen, therefore, the volume of bound oxygen depends on the amount of hemoglobin. Since in newborns during the first days of life the hemoglobin content is higher than in adults, their oxygen-binding capacity of blood is also higher. This allows the newborn to survive the critical period - the period of the formation of pulmonary respiration. This is also facilitated by a higher content of fetal hemoglobin (HbF), which has a greater affinity for oxygen than adult hemoglobin (HbA). After the establishment of pulmonary respiration, the content of HbF in the child's blood decreases rapidly. However, with hypoxia and anemia, the amount of HbF may increase again. It is, as it were, a compensatory device that protects the body (especially vital organs) from hypoxia.

The ability to bind oxygen to hemoglobin is also determined by temperature, blood pH and carbon dioxide content. With an increase in temperature, a decrease in pH, and an increase in PCO 2, the binding curve shifts to the right.

The solubility of oxygen in 100 ml of blood at RO 2 equal to 100 mm Hg. Art., is only 0.3 ml. The solubility of oxygen in the blood increases significantly with increasing pressure. An increase in oxygen pressure to 3 atm ensures the dissolution of 6% oxygen, which is sufficient to maintain tissue respiration at rest without the participation of oxyhemoglobin. This technique (oxybarotherapy) is currently used in the clinic.

Capillary blood oxygen diffuses into tissues also due to the oxygen pressure gradient in the blood and cells (in arterial blood, oxygen pressure is 90 mm Hg, in cell mitochondria it is only 1 mm Hg).

Features of tissue respiration are studied much worse than other stages of respiration. However, it can be assumed that the intensity of tissue respiration in children is higher than in adults. This is indirectly confirmed by the higher activity of blood enzymes in newborns compared to adults. One of the essential features of metabolism in young children is an increase in the proportion of the anaerobic phase of metabolism compared to that in adults.

The partial pressure of carbon dioxide in tissues is higher than in blood plasma, due to the continuity of the processes of oxidation and release of carbon dioxide, so H 2 CO 3 easily enters the blood from tissues. In the blood, H 2 CO 3 is in the form of free carbonic acid associated with erythrocyte proteins, and in the form of bicarbonates. At a blood pH of 7.4, the ratio of free carbonic acid and bound in the form of sodium bicarbonate (NаНСО 3) is always 1:20. The reaction of binding carbon dioxide in the blood with the formation of H 2 CO 3, bicarbonate and, conversely, the release of carbon dioxide from compounds in the capillaries of the lungs is catalyzed by the enzyme carbonic anhydrase, the action of which is determined by the pH of the medium. In an acidic environment (i.e., in cells, venous blood), carbonic anhydrase promotes the binding of carbon dioxide, and in an alkaline environment (in the lungs), on the contrary, it decomposes and releases it from compounds.

The activity of carbonic anhydrase in premature infants is 10%, and in full-term infants - 30% of the activity in adults. Its activity slowly increases and only by the end of the first year of life reaches the norms of an adult. This explains the fact that in various diseases (especially pulmonary), children are more likely to experience hypercapnia (accumulation of carbon dioxide in the blood).

Thus, the process of breathing in children has a number of features. They are largely determined by the anatomical structure of the respiratory system. In addition, young children have lower respiratory efficiency. All the above anatomical and functional features of the respiratory system create the preconditions for a milder respiratory failure, which leads to respiratory failure in children.

The respiratory organs in children are not only absolutely smaller, but, in addition, they also differ in some incompleteness of the anatomical and histological structure.

The child's nose is relatively small, its cavities are underdeveloped, the nasal passages are narrow; the lower nasal passage in the first months of life is completely absent or rudimentary developed. The mucous membrane is tender, rich in blood vessels, the submucosa is poor in cavernous tissue in the first years of life; at 8-9 years old, the cavernous tissue is already quite developed, and it is especially abundant during puberty.

The paranasal cavities in young children are very poorly developed or even completely absent. The frontal sinus appears only in the 2nd year of life, by the age of 6 it reaches the size of a pea and is finally formed only by the age of 15. The maxillary cavity, although already present in newborns, is very small and only from the age of 2 begins to noticeably increase in volume; approximately the same must be said of sinus ethmoidalis. Sinus sphenoidalis in young children is very small; up to 3 years of age, its contents are easily emptied into the nasal cavity; from the age of 6, this cavity begins to increase rapidly. Due to the poor development of the accessory nasal cavities in young children, inflammatory processes with the nasal mucosa very rarely spread to these cavities.

The nasolacrimal canal is short, its outer opening is located close to the corner of the eyelids, the valves are underdeveloped, which greatly facilitates the infection from the nose into the conjunctival sac.

The pharynx in children is relatively narrow and has a more vertical direction. Waldeyer's ring in newborns is poorly developed; pharyngeal tonsils are invisible when examining the pharynx and become visible only by the end of the 1st year of life; in the following years, on the contrary, accumulations of lymphoid tissue and tonsils are somewhat hypertrophied, reaching maximum expansion most often between 5 and 10 years. In puberty, the tonsils begin to undergo reverse development, and after puberty it is relatively very rare to see their hypertrophy. Adenoid expansions are most pronounced in children with exudative and lymphatic diathesis; they especially often have to observe nasal breathing disorders, chronic catarrhal conditions of the nasopharynx, sleep disturbances.

The larynx in children of the earliest age has a funnel-shaped shape, later - cylindrical; it is located slightly higher than in adults; its lower end in newborns is at the level of the IV cervical vertebra (in adults it is 1-1.5 vertebrae lower). The most vigorous growth of the transverse and anterior-posterior dimensions of the larynx is noted in the 1st year of life and at the age of 14-16 years; with age, the funnel-shaped form of the larynx gradually approaches the cylindrical. The larynx in young children is relatively longer than in adults.

The cartilages of the larynx in children are tender, very pliable, the epiglottis up to 12-13 years old is relatively narrow, and in infants it can be easily seen even with a normal examination of the pharynx.

Sexual differences in the larynx in boys and girls begin to be revealed only after 3 years, when the angle between the plates of the thyroid cartilage in boys becomes more acute. From the age of 10, the features characteristic of the male larynx are already quite clearly identified in boys.

These anatomical and histological features of the larynx explain the mild onset of stenotic phenomena in children, even with relatively mild inflammation. The hoarseness of the voice, often noted in young children after a cry, usually does not depend on inflammation, but on the lethargy of the easily fatiguing muscles of the glottis.

The trachea in newborns is about 4 cm long, by the age of 14-15 it reaches approximately 7 cm, and in adults it is 12 cm. It has a somewhat funnel-shaped shape in children of the first months of life and is located higher than in adults; in newborns, the upper end of the trachea is at the level of the IV cervical vertebra, in adults - at the level of VII. The bifurcation of the trachea in newborns corresponds to III-IV thoracic vertebrae, in children 5 years old - IV-V and 12-year-olds - V - VI vertebrae.

The growth of the trachea is approximately parallel to the growth of the trunk; between the width of the trachea and the circumference of the chest at all ages, almost constant relationships remain. The cross section of the trachea in children of the first months of life resembles an ellipse, in subsequent ages it is a circle.

The mucous membrane of the trachea is tender, rich in blood vessels, and comparatively dry, owing to insufficient secretion of the mucous glands. The muscular layer of the membranous part of the tracheal wall is well developed even in very young children; elastic tissue is in a relatively small amount.

Children's trachea is soft, easily squeezed; under the influence of inflammatory processes, stenotic phenomena easily occur. The trachea is mobile to some extent and can move under the influence of unilateral pressure (exudate, tumors).

Bronchi. The right bronchus is, as it were, a continuation of the trachea, the left bronchus departs at a large angle; this explains the more frequent entry of foreign bodies into the right bronchus. The bronchi are narrow, their cartilage is soft, the muscle and elastic fibers are relatively poorly developed, the mucosa is rich in blood vessels, but relatively dry.

The lungs of a newborn weigh about 50 g, by 6 months their weight doubles, by a year it triples, by 12 years it reaches 10 times its original weight; in adults, the lungs weigh almost 20 times more than at birth. The right lung is usually slightly larger than the left. In young children, pulmonary fissures are often weakly expressed, only in the form of shallow furrows on the surface of the lungs; especially often, the middle lobe of the right lung almost merges with the upper one. A large, or main, oblique fissure separates the lower lobe from the upper and middle lobes to the right, and a small horizontal one passes between the upper and middle lobes. There is only one gap on the left.

From the growth of the mass of the lungs, it is necessary to distinguish the differentiation of individual cellular elements. The main anatomical and histological unit of the lung is the acinus, which, however, has a relatively primitive character in children under 2 years of age. From 2 to 3 years, cartilaginous muscular bronchi develop vigorously; from the age of 6-7 years, the histostructure of the acinus basically coincides with that of an adult; the sacculuses that sometimes come across do not already have a muscular layer. Interstitial (connective) tissue in children is loose, rich in lymphatic and blood vessels. Children's lung is poor in elastic tissue, especially in the circumference of the alveoli.

The epithelium of the alveoli in non-breathing stillborns is cuboidal, in breathing newborns and in older children it is flat.

Differentiation of the children's lung, thus, is characterized by quantitative and qualitative changes: a decrease in respiratory bronchioles, the development of alveoli from the alveolar passages, an increase in the capacity of the alveoli themselves, a gradual reverse development of intrapulmonary connective tissue layers and an increase in elastic elements.

The volume of the lungs of already breathing newborns is about 67 cm 3; by the age of 15, their volume increases 10 times and in adults - 20 times. The overall growth of the lungs is mainly due to an increase in the volume of the alveoli, while the number of the latter remains more or less constant.

The breathing surface of the lungs is relatively larger in children than in adults; the contact surface of the alveolar air with the system of vascular pulmonary capillaries decreases relatively with age. The amount of blood flowing through the lungs per unit time is greater in children than in adults, which creates the most favorable conditions for gas exchange in them.

Children, especially young children, are prone to pulmonary atelectasis and hypostasis, the occurrence of which is favored by the abundance of blood in the lungs and the insufficient development of elastic tissue.

The mediastinum in children is relatively larger than in adults; in its upper part it contains the trachea, large bronchi, thymus and lymph nodes, arteries and large nerve trunks, in its lower part are the heart, blood vessels and nerves.

The lymph nodes. The following groups of lymph nodes in the lungs are distinguished: 1) tracheal, 2) bifurcation, 3) bronchopulmonary (at the entry of the bronchi into the lungs) and 4) nodes of large vessels. These groups of lymph nodes are connected by lymphatic routes with the lungs, mediastinal and supraclavicular nodes (Fig. 48).

Rice. 48. Topography of mediastinal lymph nodes (according to Sukennikov).
1 - lower tracheobronchial;
2 - upper tracheobronchial;
3 - paratracheal;
4 - bronchopulmonary nodes.

Rib cage. Relatively large lungs, heart and mediastinum occupy relatively more space in the child's chest and predetermine some of its features. The chest is always in a state of inhalation, the thin intercostal spaces are smoothed out, and the ribs are quite strongly pressed into the lungs.

The ribs in very young children are almost perpendicular to the spine, and it is almost impossible to increase the capacity of the chest by raising the ribs. This explains the diaphragmatic nature of breathing at this age. In newborns and infants in the first months of life, the anterior-posterior and lateral diameters of the chest are almost equal, and the epigastric angle is very obtuse.

With the age of the child, the cross section of the chest takes an oval or kidney-shaped shape. The frontal diameter increases, the sagittal diameter relatively decreases, and the curvature of the ribs increases significantly; the epigastric angle becomes more acute.

These ratios are characterized by a chest indicator (the percentage ratio between the anterior-posterior and transverse diameters of the chest): in the fetus of the early embryonic period it is 185, in the newborn 90, by the end of the year - 80, by 8 years - 70, after the pubertal period it is again somewhat increases and fluctuates around 72-75.

The angle between the costal arch and the medial section of the chest in a newborn is approximately 60 °, by the end of the 1st year of life - 45 °, at the age of 5 years - 30 °, at 15 years - 20 ° and after the end of puberty - about 15 °.

The position of the sternum also changes with age; its upper edge, lying in a newborn at the level of the VII cervical vertebra, by the age of 6-7 falls to the level of the II-III thoracic vertebrae. The dome of the diaphragm, reaching the upper edge of the IV rib in infants, falls slightly lower with age.

From the foregoing, it can be seen that the chest in children gradually passes from the inspiratory position to the expiratory one, which is the anatomical prerequisite for the development of the thoracic (costal) type of breathing.

The structure and shape of the chest can vary significantly depending on the individual characteristics of the child. The shape of the chest in children is especially easily affected by past diseases (rickets, pleurisy) and various negative environmental influences. Age-related anatomical features of the chest also determine some physiological features of the breathing of children in different periods of childhood.

First breath of a newborn. During intrauterine development in the fetus, gas exchange takes place exclusively due to the placental circulation. At the end of this period, the fetus develops correct intrauterine respiratory movements, indicating the ability of the respiratory center to respond to irritation. From the moment the child is born, gas exchange stops due to the placental circulation and pulmonary respiration begins.

The physiological causative agent of the respiratory center is carbon dioxide, the increased accumulation of which since the termination of placental circulation is the cause of the first deep breath of the newborn; it is possible that the cause of the first breath should be considered not an excess of carbon dioxide in the blood of a newborn, but a lack of oxygen in it.

The first breath, accompanied by the first cry, in most cases appears in the newborn immediately - as soon as the passage of the fetus through the mother's birth canal ends. However, in those cases when a child is born with a sufficient supply of oxygen in the blood or there is a slightly reduced excitability of the respiratory center, it takes several seconds, and sometimes even minutes, until the first breath appears. This brief breath holding is called neonatal apnea.

After the first deep breath, normal and mostly fairly regular breathing is established in healthy children; the unevenness of the respiratory rhythm noted in some cases during the first hours and even days of a child's life usually quickly levels off.

Respiratory rate in newborns, about 40-60 per minute; with age, breathing becomes more rare, gradually approaching the rhythm of an adult. According to our observations, the respiratory rate in children is as follows.

Up to 8 years, boys breathe more often than girls; in the prepubertal period, girls overtake boys in respiratory rate, and in all subsequent years their breathing remains more frequent.

Children are characterized by mild excitability of the respiratory center: mild physical stress and mental arousal, slight increases in body temperature and ambient air almost always cause a significant increase in breathing, and sometimes some disturbance in the correctness of the respiratory rhythm.

For one respiratory movement in newborns, on average, there are 272-3 pulse beats, in children at the end of the 1st year of life and older - 3-4 beats, and, finally, in adults - 4-5 heartbeats. These ratios usually persist with increased heart rate and respiration under the influence of physical and mental stress.

Breathing volume. To assess the functional ability of the respiratory system, the volume of one respiratory movement, the minute volume of respiration and the vital capacity of the lungs are usually taken into account.

The volume of each respiratory movement in a newborn in a state of restful sleep is on average 20 cm 3, in a month-old child it rises to approximately 25 cm 3, by the end of the year it reaches 80 cm 3, by 5 years - about 150 cm 3, by 12 years - in on average, about 250 cm 3 and by the age of 14-16 it rises to 300-400 cm 3; however, this value, apparently, can fluctuate within fairly wide individual limits, since the data of various authors differ greatly. When crying, the volume of breathing increases sharply - by 2-3 and even 5 times.

The minute volume of respiration (the volume of one breath multiplied by the respiratory rate) increases rapidly with age and approximately equals 800-900 cm 3 in a newborn, 1400 cm 3 in a child aged 1 month, and about 2600 cm 3 by the end of the 1st year , at the age of 5 years - about 3200 cm 3 and at 12-15 years old - about 5000 cm 3.

The vital capacity of the lungs, i.e., the amount of air exhaled as much as possible after a maximum breath, can only be indicated for children from 5-6 years old, since the research methodology itself requires the active participation of the child; at 5-6 years old, the vital capacity fluctuates around 1150 cm 3, at 9-10 years old - about 1600 cm 3 and at 14-16 years old - 3200 cm 3. Boys have greater lung capacity than girls; The greatest lung capacity occurs with thoraco-abdominal breathing, the smallest - with purely chest.

The type of breathing varies depending on the age and sex of the child; in children of the neonatal period, diaphragmatic breathing predominates with little participation of the costal muscles. In infants, the so-called thoraco-abdominal breathing with a predominance of diaphragmatic is detected; chest excursions are weakly expressed in its upper parts and, conversely, much stronger in the lower parts. With the transition of the child from a constant horizontal position to a vertical position, the type of breathing also changes; it at this age (the beginning of the 2nd year of life) is characterized by a combination of diaphragmatic and chest breathing, and in some cases one prevails, in others the other. At the age of 3-7 years, in connection with the development of the muscles of the shoulder girdle, chest breathing becomes more and more distinct, beginning to definitely dominate diaphragmatic breathing.

The first differences in the type of breathing depending on sex begin to clearly affect at the age of 7-14 years; in the prepubertal and pubertal periods, boys develop mainly the abdominal type, and girls develop the chest type of breathing. Age-related changes in the type of breathing are predetermined by the above anatomical features of the chest of children in different periods of life.

Increasing chest capacity by raising the ribs in infants is almost impossible due to the horizontal position of the ribs; it becomes possible in later periods, when the ribs descend somewhat downward and anteriorly, and when they are raised, an increase in the anterior-posterior and lateral dimensions of the chest occurs.

One of the actions carried out during the examination by a pediatrician is the counting of respiratory movements. This seemingly simple indicator carries important information about the state of health in general and about the functioning of the respiratory and cardiovascular systems in particular.

How to correctly calculate the frequency of respiratory movements (RR) per minute? This is not particularly difficult. However, there are some difficulties in interpreting the data. This is more true for young parents, because, having received a result from a child that is several times higher than their own, they panic. Therefore, in this article, we still propose to figure out what is the norm of NPV in children. The table will help us with this.

Features of the child's respiratory system

The first thing that the expectant mother has been waiting for so long is the first cry of the baby. It is with this sound that his first breath occurs. By the time of birth, the organs that ensure the respiration of the child are not yet fully developed, and only with the growth of the organism itself do they mature (both functionally and morphologically).

The nasal passages (which are the upper respiratory tract) in newborns have their own characteristics:
. They are quite narrow.
. Relatively short.
. Their inner surface is tender, with a huge number of vessels (blood, lymph).

Therefore, even with minor nasal mucosa in a child, it quickly swells, and the small lumen decreases, as a result, breathing becomes difficult, shortness of breath develops: young children cannot yet breathe through their mouths. The younger the child, the more dangerous the consequences can be, and the faster it is necessary to eliminate the pathological condition.

Lung tissue in young children also has its own characteristics. They, unlike adults, have poorly developed lung tissue, and the lungs themselves have a small volume with a huge number of blood vessels.

Rules for counting the respiratory rate

Measuring the respiratory rate does not require any special skills or equipment. All you need is a stopwatch (or a clock with a second hand) and following some simple rules.

The person should be in a calm state and in a comfortable position. If we are talking about children, especially at an early age, then the calculation of respiratory movements is best done in a dream. If this is not possible, the subject should be distracted from the manipulation as much as possible. To do this, it is enough to take hold of the wrist (where the pulse is usually determined) and in the meantime count the respiratory rate. It should be noted that the pulse in children under one year old (about 130-125 beats per minute) should not cause concern - this is the norm.

In infants, it is strongly recommended to count the respiratory rate during sleep, since crying can significantly affect the result and give obviously false numbers. By placing your hand on the anterior abdominal wall (or just visually), you can easily conduct this study.

Given that breathing has its own rhythmic cycle, it is necessary to observe the duration of its calculation. Be sure to measure the respiratory rate for a full minute, and not multiply the result obtained in just 15 seconds by four. It is recommended to carry out three counts and calculate the average value.

Norm of respiratory rate in children

The table shows the norms of the frequency of respiratory movements. Data are presented for children of different age groups.

As you can see from the table, the frequency of respiratory movements per minute is higher, the younger the child. Gradually, as they grow older, their number decreases, and by the pubertal period, when the child is 14-15 years old, the respiratory rate becomes equal to this indicator in an adult healthy person. No gender differences are observed.

Breath types

There are three main types of breathing in both adults and children: thoracic, abdominal, and mixed.

The chest type is more characteristic of the female representative. With it, inhalation / exhalation is provided to a greater extent due to the movements of the chest. The disadvantage of this type of respiratory movements is poor ventilation of the lower parts of the lung tissue. Whereas in the abdominal type, when the diaphragm is more involved (and the anterior abdominal wall visually moves during breathing), the upper sections of the lungs experience a lack of ventilation. This type of respiratory movements is more typical for men.

But with a mixed type of breathing, a uniform (equal) expansion of the chest occurs with an increase in the volume of its cavity in all four directions (upper-lower, lateral). This is the most correct one that provides optimal ventilation of the entire lung tissue.

Normally, the respiratory rate in a healthy adult is 16-21 per minute, in newborns - up to 60 per minute. Above, the rate of respiratory rate in children is given in more detail (table with age norms).

Rapid breathing

The first sign of damage to the respiratory system, especially in infectious diseases, is. At the same time, there will certainly be other signs of a cold (cough, runny nose, wheezing, etc.). Quite often, with an increase in body temperature, the respiratory rate increases and the pulse quickens in children.

Holding your breath during sleep

Quite often, in young children (especially infants) in a dream, there are short-term respiratory arrests in duration. This is a physiological feature. But if you notice that such episodes become more frequent, their duration becomes longer, or other symptoms occur, such as blue lips or loss of consciousness, you should immediately call an ambulance to prevent irreversible consequences.

Conclusion

The respiratory organs have a number of features that contribute to their frequent damage and rapid decompensation of the condition. This is primarily due to their immaturity at the time of birth, certain anatomical and physiological features, incomplete differentiation of the structures of the central nervous system and their direct effect on the respiratory center and respiratory organs.
The younger the child, the less lung capacity he has, so, therefore, he will need to make more respiratory movements (inhalation / exhalation) in order to provide the body with the necessary amount of oxygen.

Summing up

It should be remembered that in children of the first months of life, respiratory arrhythmia is quite common. Most often, this is not a pathological condition, but only indicates age-related features.

So, now you know what the rate of NPV in children is. The table of averages should be taken into account, but small deviations should not be panicked. And be sure to check with your doctor before jumping to conclusions!

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 has rhythmic, respiratory movements with a frequency of 38-70 per minute. These breathing movements are reduced to a slight expansion of the chest, which is followed by a longer collapse 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 lower values ​​of gas partial tension in tissues. By the end of pregnancy, the content of HbF decreases to 40%. The tension of carbon dioxide (PC0 2) in the arterial blood of the fetus (35-45 mm Hg. Art.) is 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) excessive accumulation of 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 area of ​​the nostrils, the amniotic fluid (diver's reflex) stops the inhibition of the respiratory center. Excitation of the inspiratory muscles (diaphragm) occurs, which causes an increase in the volume of the chest cavity and a decrease in 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).

During the implementation of the first breath, a significant elasticity of the lung tissue is overcome, due to the surface tension force of the collapsed alveoli. During the first breath, energy is expended 10-15 times more than in subsequent breaths. To stretch the lungs of children who have not yet breathed, the pressure of the air flow must be approximately 3 times greater than in children who have switched to spontaneous breathing.

Facilitates the first breath of a surfactant - a 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 expiration is equal to atmospheric pressure, during inspiration it decreases and becomes negative (in adults it is negative both during inspiration and during expiration).

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 pulmonary circulation, the blood circulation through the pulmonary circulation changes. An open arterial (botallian) duct in the first days, and sometimes weeks, can maintain hypoxia by directing part of the blood from the pulmonary artery to the aorta, bypassing the small 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 expended on breathing, compared with adults, is greater, since, firstly, diaphragmatic breathing predominates, since the ribs are located horizontally, perpendicular to the spinal column, which limits the excursion of the chest. This type of breathing remains the leading one in children up to 3-7 years of age. It requires overcoming the resistance of the abdominal organs (children have a relatively large liver and frequent intestinal swelling); 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 is 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 up an upright position, breathing becomes chest-abdominal. From the age of 3-7, due to the development of the muscles of the shoulder girdle, the thoracic type of breathing begins to predominate 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 of different ages (V.A. Doskin et al., 1997)

Table 6.2

Age	VC, ml	Volume, ml
		respiratory	reserve exhalation	reserve breath
adults	4000-

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

The increase in 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 airways, a decrease in elastic resistance to breathing due to an increase in the proportion of elastic fibers in the lungs relative to collagen by increasing the strength of the respiratory muscles. Therefore, the energy cost of breathing is reduced (Table 6.3).