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 6 weeks embryonic development The child develops branches of the second order respiratory organs. At the same time, the formation of the lungs begins. By 12 weeks prenatal 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. Crucial It has proper development nervous system, which is involved in the breathing process.

Upper respiratory tract

In newborn babies, the skull bones 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 blood vessels. It is more vulnerable than that of 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 develops a lower nasal passage. In children paranasal sinuses are located differently than in adults, due to which the infection can quickly spread into the cranial cavity.

In children, there is severe growth in the nasopharynx lymphoid tissue. 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 a 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 the immune system.

Larynx

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

Trachea

The structure of the trachea also differs in children. During the first year of life, it is narrow and funnel-shaped. By age 15 top part trachea reaches 4 cervical vertebra. By this time, the length of the trachea doubles, it is 7 cm. In children, it is very soft, so when the nasopharynx is inflamed, it is often compressed, which manifests itself as stenosis.

Bronchi

The right bronchus is like a continuation of the trachea, and the left one moves to the side at an angle. That is why in case of accidental hit foreign objects into the nasopharynx, they often end up in the right bronchus.

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

Lungs

Children's lungs undergo changes as they grow older. The mass and size of these respiratory organs increase, and differentiation in their structure also occurs. 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 and contains less air than in adults. By the age of 7, the formation of the acini ends, and until the age of 12, the growth of the formed tissue simply continues. By the age of 15, the alveoli increase 3 times.

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

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 chest is oval in shape. Children's ribs are located in a special way; due to their structure, a child can painlessly transition from diaphragmatic to chest breathing.

Peculiarities of breathing in a child

Children have an increased respiratory rate, with respiratory movements becoming more frequent the more smaller child. From the age of 8, boys breathe more often than girls, but starting from adolescence, the girls begin to breathe more often and this state of affairs continues throughout the entire time.

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

• Overall volume breathing 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 exercise or sports exercises. The more exercise stress, the more noticeable is the change in breathing pattern.

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 increases. The amount of air that the lungs can ventilate in a minute is called the respiratory limit. This value also increases as the child grows older.

Huge value for assessment pulmonary function has gas exchange. Content 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 child’s respiratory organs, the doctor collects an anamnesis. Carefully studied Medical Card little patient, 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 produced. Then the examination takes place according to the following algorithm:

• The mother is asked how the pregnancy progressed and whether there were any complications during childbirth. In addition, it is important what the baby was sick with shortly before the appearance 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 nasal discharge. Look at the color 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 experiences short-term pauses in breathing during sleep. If this condition is typical, then this may indicate problems of a neurological nature.
• X-rays are prescribed to clarify the diagnosis if pneumonia or other lung pathologies are suspected. X-rays can be performed even on children early age, if there are indications for this procedure. To reduce the level of radiation exposure, it is recommended that children be examined using digital devices.
• Examination using a bronchoscope. It is carried out for bronchitis and suspicion of a foreign body entering the bronchi. Using a bronchoscope, the foreign body is removed from the respiratory organs.
• Computed tomography is performed if there is a suspicion of oncological diseases. This method, although expensive, is the most accurate.

For children younger age bronchoscopy is performed under general anesthesia. This eliminates respiratory injuries during the examination.

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

Oxygen reserves in the body are very limited, and they last for 5-6 minutes. The body is supplied with oxygen through the process of breathing. Depending on the function performed, there are 2 main parts of the lung: conductive part to supply air into the alveoli and remove it out and respiratory part, where gas exchange occurs between air and blood. The conducting part includes the larynx, trachea, bronchi, i.e., the bronchial tree, and the respiratory part itself includes the acini, consisting of afferent bronchioles, alveolar ducts 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 through 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 inspired and alveolar air, arterial and venous blood (mmHg)

Index	Inhaled air	Alveolar air	Arterial blood	Deoxygenated blood
RO 2
RSO 2
RN 2
RN 2 ABOUT
Total 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 transfer 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 effectiveness of the external respiratory system function is determined by three processes: ventilation of the alveolar space, adequate ventilation of the lungs by capillary blood flow (perfusion), and diffusion of gases through the alveolar-capillary membrane. Compared to adults, children, especially the first year of life, have pronounced differences external respiration. This is explained by the fact that in the postnatal period there is further development of the respiratory parts 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, external respiration function is assessed using the following groups of indicators.

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

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

Mechanics of breathing - maximum ventilation lungs (MVL, Vmax), or breathing limit, respiratory reserve, forced vital capacity (FEV) and its relation to vital capacity (Tiffno index), bronchial resistance, volumetric flow rate of inhalation and exhalation during quiet and forced breathing.

Pulmonary gas exchange- the amount of oxygen consumption and carbon dioxide release per minute, the composition of alveolar air, the oxygen utilization rate.

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

The depth of breathing, or tidal volume (DO, or Vt, in ml), in children, both in absolute and relative numbers, is significantly 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. Shalkova
	Abs. number	Per 1 kg body weight	Abs. number	Per 1 kg body weight
Newborn
Adults

This is due to two reasons. One of them, naturally, is the small weight of the lungs in children, which increases with age, and during the first 5 years mainly due to the formation of alveoli. Another, no less important reason that explains the shallow breathing of young children is the structural features of the chest (the anterior-posterior size is approximately equal to the lateral size, the ribs extend from the spine almost at a right angle, which limits the excursion of the chest and changes in lung volume). The latter changes mainly due to the movement of the diaphragm. An increase in tidal volume at rest may indicate respiratory failure, and a decrease in tidal volume 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 intense metabolism. Thus, 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 2 years it increases slightly (8.5 ml/min), by 6 years 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 shallow nature of breathing and its irregularity are compensated by a higher breathing frequency (f). So, in a newborn - 40-60 breaths per minute, 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 per minute. The respiratory rate reflects the compensatory capabilities of the body, but in combination with a small tidal volume, tachypnea indicates respiratory failure. Due to the higher respiratory rate, per 1 kg of body weight, the minute volume of breathing is significantly higher in children, especially young children, than in adults. In children under 3 years of age, the minute volume of breathing is almost 1.5 times greater than that of an 11-year-old child, and more than 2 times that of an adult (Table 4).

Table 4

Minute volume of breathing in children

Indicators	Newborn cash	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 effective breathing for providing the body with oxygen. It is interesting to note that a warm hygienic bath causes a 2-fold increase in pulmonary ventilation, and this increase occurs mainly due to an increase in the depth of breathing. Hence, 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, becomes quite understandable.

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

Table 5

Vital capacity of the lungs

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

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

Inspiratory reserve volume(ROVD, 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, ROVD/VC ranges from 55 to 59%. A decrease in this indicator is observed with restrictive (limiting) lesions, especially with a decrease in elasticity lung tissue.

Expiratory reserve volume(ROvyd, ERV) - the maximum volume of air (in milliliters) that can be exhaled after a quiet inhalation. Just as for the inspiratory reserve volume, its relationship to vital capacity (Vc) is important for assessing ERV. In children aged 6 to 15 years, ROV/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 maximum inspiration.

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

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, as signs of hyperventilation may occur (dizziness, vomiting, fainting). 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

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

Table 7

Breathing reserve in children

Age, years	Breathing reserve, l/min	Age, years	Breathing reserve, l/min

The effectiveness of external respiration is judged by the difference in oxygen and carbon dioxide content 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%. The exhaled air of young children contains less carbon dioxide - 2.5%, in adults - 4%. Thus, young children absorb less oxygen and emit less carbon dioxide per breath, although gas exchange in children is more significant than in adults (calculated per 1 kg of body weight).

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

KIO 2 =PO 2 (ml/min) / MOD (l/min).

In children under 5 years of age, CIR 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 circle.

Oxygen is transported from the lungs to the tissues by 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 newborns have a higher hemoglobin content during the first days of life than adults, the oxygen-binding capacity of their blood is higher. This allows the newborn to survive a critical period - the period of formation of pulmonary respiration. This is also facilitated by more high content fetal hemoglobin (HbF), which has a greater affinity for oxygen than adult hemoglobin (HbA). After pulmonary respiration is established, the HbF content in the child’s blood quickly decreases. However, with hypoxia and anemia, the amount of HbF may increase again. This is like a compensatory device that protects the body (especially vital organs) from hypoxia.

The ability to bind oxygen by hemoglobin is also determined by temperature, blood pH and carbon dioxide content. With increasing temperature, decreasing pH and increasing PCO 2, the binding curve shifts to the right.

The solubility of oxygen in 100 ml of blood at PO 2 equal to 100 mm Hg. Art., is only 0.3 ml. The solubility of oxygen in the blood increases significantly with increasing pressure. Increasing the 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 the oxygen pressure is 90 mm Hg, in the mitochondria of cells it is only 1 mm Hg).

The features of tissue respiration have been studied much less well 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 significant 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, therefore H 2 CO 3 easily enters the blood from tissues. In the blood, H 2 CO 3 is found in the form of free carbonic acid bound to 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 (NaHCO 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 environment. 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 newborns is 10%, and in full-term newborns it is 30% of the activity in adults. Her 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 with various diseases (especially pulmonary diseases), children more often experience hypercapnia (accumulation of carbon dioxide in the blood).

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

The respiratory organs in children not only have an absolutely smaller size, but, in addition, they also differ in some incomplete anatomical and histological structure.

The child’s nose is relatively small, its cavities are underdeveloped, and the nasal passages are narrow; The lower nasal passage in the first months of life is completely absent or rudimentarily 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 there is especially a lot of it during puberty.

The accessory nasal cavities in young children are very poorly developed or even completely absent. Frontal sinus appears only in the 2nd year of life, by 6 years it reaches the size of a pea and is finally formed only by 15 years. 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 about 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 years, this cavity begins to rapidly increase. Due to the poor development of the paranasal cavities in young children, inflammatory processes from the nasal mucosa very rarely spread to these cavities.

The nasolacrimal duct is short, its external opening is located close to the corner of the eyelids, the valves are underdeveloped, which makes it very easy for infection to enter the conjunctival sac from the nose.

The pharynx in children is relatively narrow and has more vertical direction. Waldeyer's ring in newborns is poorly developed; pharyngeal tonsils upon examination, the pharynx is invisible and becomes visible only by the end of the 1st year of life; V next years On the contrary, accumulations of lymphoid tissue and tonsils hypertrophy somewhat, reaching maximum expansion most often between 5 and 10 years. During puberty, the tonsils begin to undergo reverse development, and after puberty it is relatively rare to see their hypertrophy. Enlargements of the adenoids are most pronounced in children with exudative and lymphatic diathesis; they especially often experience nasal breathing disorders, chronic catarrhal conditions of the nasopharynx, and sleep disturbances.

The larynx in very young children 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 fourth cervical vertebra (in adults it is 1 - 1.5 vertebrae lower). The most vigorous growth of the transverse and anteroposterior dimensions of the larynx is observed in the 1st year of life and at the age of 14-16 years; With age, the funnel-shaped shape of the larynx gradually approaches cylindrical. The larynx in young children is relatively longer than in adults.

The cartilage of the larynx in children is delicate, very pliable, the epiglottis is relatively narrow until the age of 12-13, and in infants it can be easily seen even with a routine examination of the pharynx.

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

The indicated anatomical and histological features of the larynx explain the mild onset of stenotic phenomena in children, even with relatively moderate inflammatory phenomena. Hoarseness, often observed in young children after crying, usually does not depend on inflammatory phenomena, but from lethargy of the easily fatigued muscles of the glottis.

The trachea in newborns has a length of about 4 cm, by the age of 14-15 it reaches approximately 7 cm, and in adults it is 12 cm. In children of the first months of life, it has a somewhat funnel-shaped shape and is located higher in them 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 the III-IV thoracic vertebrae, in 5-year-old children - IV-V and 12-year-olds - V-VI vertebrae.

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

The tracheal mucosa is tender, rich in blood vessels and relatively dry due to insufficient secretion of mucous glands. Muscle layer the membranous part of the tracheal wall is well developed even in very young children; elastic tissue is found in relatively small quantities.

A child's trachea is soft and easily compressed; influenced inflammatory processes Stenotic phenomena easily occur. The trachea is mobile to some extent and can be displaced under the influence of unilateral pressure (exudate, tumor).

Bronchi. The right bronchus is like a continuation of the trachea, the left one extends at a large angle; this explains more frequent hit foreign bodies into the right bronchus. The bronchi are narrow, their cartilage is soft, 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 one year it triples, and 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, the pulmonary fissures are often weakly expressed, only in the form of shallow grooves on the surface of the lungs; especially often the middle share right lung almost merges with the top. The large, or main, oblique fissure separates the lower lobe on the right from the upper and middle lobes, and the small horizontal fissure runs between the upper and middle lobes. There is only one slot on the left.

It is necessary to distinguish from the growth of lung mass 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 6-7 years of age, the histostructure of the acinus basically coincides with that of an adult; The sacculi that are sometimes encountered no longer have a muscular layer. Interstitial (connective) tissue in children is loose and rich in lymphatic and blood vessels. The children's lung is poor in elastic tissue, especially around the alveoli.

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

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

The lung volume 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 occurs 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 in children is relatively larger than in adults; The contact surface of the alveolar air with the vascular pulmonary capillary system 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 richness of the lungs in blood and 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 gland and lymph nodes, arteries and large nerve trunks, in its lower part there are the heart, blood vessels and nerves.

The lymph nodes. Distinguish the following groups lymph nodes in the lungs: 1) tracheal, 2) bifurcation, 3) bronchopulmonary (at the point where the bronchi enter the lungs) and 4) nodes of large vessels. These groups of lymph nodes are connected by lymphatic pathways to the lungs, mediastinal and supraclavicular nodes (Fig. 48).

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

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

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

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

These ratios are characterized by the chest indicator ( percentage between the anteroposterior 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 puberty it increases slightly again 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 years falls to level II-III thoracic vertebrae. The dome of the diaphragm, which reaches the upper edge of the fourth rib in infants, drops somewhat lower with age.

From the above it is clear that the chest in children gradually moves from the inspiratory position to the expiratory position, 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 individual characteristics child. The shape of the chest in children is especially easily affected by past illnesses(rickets, pleurisy) and various negative impacts environment. Age-related anatomical features of the chest also determine some physiological features of the breathing of children in different periods childhood.

Newborn's first breath. During intrauterine development in the fetus, gas exchange occurs exclusively due to placental circulation. At the end of this period, the fetus develops regular intrauterine respiratory movements, indicating the ability respiratory center react to irritation. From the moment the baby 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 from the moment of cessation of placental circulation is the cause of the first take a deep breath newborn; it is possible that the cause of the first breath should be considered not an excess of carbon dioxide in the newborn’s blood, 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 birth canal mother. However, in cases where a child is born with a sufficient supply of oxygen in the blood or there is a slightly reduced excitability of the respiratory center, several seconds, and sometimes even minutes, pass until the first breath appears. This short-term holding of breath is called neonatal apnea.

After the first deep breath, healthy children establish correct and mostly fairly uniform breathing; unevenness noted in some cases during the first hours and even days of a child’s life respiratory rhythm usually levels out quickly.

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.

Until the age of 8, boys breathe more frequently than girls; In the prepubertal period, girls are ahead of boys in breathing frequency, and in all subsequent years their breathing remains more frequent.

Children are characterized by mild excitability of the respiratory center: lungs physical stress and mental arousal, minor increases body and ambient air temperatures almost always cause a significant increase in breathing, and sometimes some disruption of the correct respiratory rhythm.

On average, one respiratory movement in newborns accounts for 272-3 pulse beat, in children at the end of the 1st year of life and older - 3-4 heartbeats, and, finally, in adults - 4-5 heartbeats. These ratios usually persist when heart rate and breathing increase under the influence of physical and mental stress.

Breath volume. To assess the functional capacity of the respiratory organs, the volume of one respiratory movement, minute volume of breathing and vital capacity of the lungs are usually taken into account.

The volume of each respiratory movement in a newborn is able to good sleep equals on average 20 cm 3, y one month old baby 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 - on average about 250 cm 3 and by 14-16 years it rises to 300-400 cm 3; however, this value, apparently, can fluctuate within fairly wide individual limits, since the data various authors diverge greatly. When screaming, the volume of breathing increases sharply - 2-3 and even 5 times.

The minute volume of breathing (the volume of one breath multiplied by the breathing frequency) quickly increases with age and is approximately equal to 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 1 year. , at the age of 5 years - about 3200 cm 3 and at 12-15 years - about 5000 cm 3.

The vital capacity of the lungs, i.e. the amount of air maximally exhaled after maximal inhalation, can only be indicated for children starting from 5-6 years old, since the research methodology itself requires active participation child; at 5-6 years old the vital capacity fluctuates around 1150 cm3, at 9-10 years old - about 1600 cm3 and at 14-16 years old - 3200 cm3. Boys have a larger lung capacity than girls; The greatest lung capacity occurs with thoraco-abdominal breathing, the smallest with purely chest breathing.

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

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

Increasing the capacity of the chest by raising the ribs in infants is almost impossible due to the horizontal position of the ribs; it becomes possible in more later periods when the ribs drop slightly downwards and anteriorly and when they are raised, the anteroposterior and side dimensions chest.

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

How to correctly calculate the respiratory rate (RR) per minute? This is not particularly difficult. But certain difficulties arise with the interpretation of 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 propose to figure out which NPV norm in children. The table will help us with this.

Features of the child's respiratory system

The first thing you've been waiting for so long future mom- the baby's first cry. It is with this sound that his first breath occurs. By the time of birth, the organs that ensure the child’s breathing are not yet fully developed, and only with the growth of the body 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 delicate, with a huge number of vessels (blood, lymphatic).

Therefore, even with minor symptoms, the child’s nasal mucosa quickly swells, the already small lumen decreases, and as a result, breathing becomes difficult and shortness of breath develops: small children cannot yet breathe through their mouths. How younger 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 at a huge number blood vessels.

Rules for counting breathing rate

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

The person must be in a calm state and in comfortable position. If we're talking about For children, especially young children, it is better to count respiratory movements during sleep. If this is not possible, the subject should be distracted from the manipulation as much as possible. To do this, just grab your wrist (where the pulse is usually detected) and meanwhile count your breathing 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 cause to a large extent influence the result and provide deliberately false figures. By placing your hand on the anterior abdominal wall (or just visually), you can easily carry out this study.

Considering that breathing has its own rhythmic cycle, it is necessary to observe the duration of its counting. Be sure to spend NPV measurement for a full minute, rather than multiplying the result obtained in just 15 seconds by four. It is recommended to carry out three counts and calculate the average.

Normal respiratory rate in children

The table shows the normal respiratory rate. Data are presented for children of different age groups.

As we 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 puberty When a child turns 14-15 years old, the respiratory rate becomes equal to that of a healthy adult. No differences by gender are observed.

Types of breathing

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

The breast type is more typical for females. With it, inhalation/exhalation is ensured to a greater extent due to movements of the chest. The disadvantage of this type of breathing movement is poor ventilation. lower sections lung tissue. Whereas with the abdominal type, when the diaphragm is more involved (and the anterior one visually moves when breathing abdominal wall), the upper parts of the lungs experience a lack of ventilation. This type of breathing movement is more common for men.

But when mixed type breathing occurs uniform (identical) expansion of the chest with an increase in the volume of its cavity in all four directions (upper-lower, lateral). This is the most correct one, which ensures 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 norm of respiratory rate in children is given in more detail (table with age norms).

Rapid breathing

The first sign of respiratory damage, especially when infectious diseases, is However, there will certainly be other signs colds(cough, runny nose, wheezing, etc.). Quite often, when body temperature rises, the respiratory rate increases and the pulse quickens in children.

Holding your breath during sleep

Quite often, young children (especially infants) experience short-term pauses in breathing during sleep. This 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 " 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 characteristics, incomplete differentiation of the structures of the central nervous system and their direct influence on the respiratory center and respiratory organs.
The younger the child, the less lung capacity he has, and therefore the more he will need to do large quantity respiratory movements (inhalation/exhalation) to provide the body with the necessary amount of oxygen.

Summing up

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

So, now you know what the normal respiratory rate is for children. The table of averages should be taken into account, but there is no need to panic when small deviations. And be sure to consult your doctor before jumping to conclusions!

Fetal breathing. In intrauterine life, the fetus receives 0 2 and removes CO 2 exclusively through placental circulation. However, the large thickness of the placental membrane (10-15 times thicker than the pulmonary membrane) does not allow equalization of partial gas tensions on both sides. The fetus develops rhythmic, respiratory movements with a frequency of 38-70 per minute. These breathing movements amount to a slight expansion of the chest, which is followed by a longer contraction and an even longer pause. In this case, the lungs do not expand, remain collapsed, the alveoli and bronchi are filled with fluid, which is secreted by alveolocytes. Only a slight negative pressure arises in the interpleural fissure as a result of the separation of the outer (parietal) layer of the pleura and an increase in its volume. The fetal breathing movements occur with the glottis closed, and therefore amniotic fluid does not enter the respiratory tract.

The significance of the fetal respiratory movements: 1) they help to increase the speed of blood movement through the vessels and its flow to the heart, and this improves 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 gas transport by blood. Oxygen tension (P0 2) in oxygenated blood umbilical vein low (30-50 mm Hg), the content of oxyhemoglobin (65-80%) and oxygen (10-150 ml/l of blood) is reduced, and therefore there is even less of it in the vessels of the heart, brain and other organs. However, the fetus has fetal hemoglobin (HbF), which has a high affinity for 0 2 , which improves the oxygen supply to cells due to the dissociation of oxyhemoglobin at lower values ​​of partial gas tension in the tissues. By the end of pregnancy, the HbF content decreases to 40%. The carbon dioxide tension (PC0 2) in the arterial blood of the fetus (35-45 mm Hg) is low due to hyperventilation of pregnant women. Red blood cells lack the enzyme carbonic anhydrase, as a result of which up to 42% of carbon dioxide, which can combine with bicarbonates, is excluded from transport and gas exchange. Mainly physical dissolved CO2 is transported through the placental membrane. By the end of pregnancy, the content of CO 2 in the fetal blood 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 predominate over aerobic ones; The energy costs of the fetus are minimal.

Breathing of a newborn. From the moment the baby is born, even before the umbilical cord is clamped, pulmonary breathing begins. The lungs expand completely after the first 2-3 breathing movements.

The causes of the first breath are:

• 1) excess accumulation CO 2 and H + and depletion of 0 2 blood after cessation of placental circulation, which stimulates central chemoreceptors;
• 2) changes in living conditions, a particularly powerful factor is 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 respiratory tract, which during 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 nostril area by the amniotic fluid (diver's reflex), the inhibition of the respiratory center stops. The inspiratory muscles (diaphragm) are excited, which causes an increase in volume chest cavity and a decrease in intrapleural pressure. The inhalation volume turns out to be greater than the exhalation volume, which leads to the formation of an alveolar air supply (functional residual capacity). Exhalation in the first days of life is carried out actively with the participation of expiratory muscles (exhalation muscles).

When taking the first breath, the significant elasticity of the lung tissue, caused by the force of surface tension of the collapsed alveoli, is overcome. 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 air flow pressure must be approximately 3 times greater than in children who have switched to spontaneous breathing.

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

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

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

With the onset of pulmonary respiration due to expansion of the lungs, acceleration of blood flow and reduction vascular bed in the pulmonary circulatory system, blood circulation through the pulmonary circulation changes. The open ductus arteriosus (botallus) 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 lesser circle.

Features of frequency, depth, rhythm and type of breathing in children. Children's breathing is frequent and shallow. This is due to the fact that the work spent on breathing, compared to adults, is greater, since, firstly, diaphragmatic breathing predominates, since the ribs are located horizontally, perpendicular spinal column, which limits chest excursion. This type of breathing remains dominant 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 bloating 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, compared to 75 m2 in adults).

The respiratory rate 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 changes significantly more than in adults under the influence of various influences(mental excitement, physical activity, increased body and environmental temperature). This is explained by the slight excitability of the respiratory center in children.

Up to 8 years of age, the breathing rate in boys is slightly higher than in girls. By puberty, the respiratory rate in girls becomes higher, and this ratio persists throughout life.

Breathing rhythm. In newborns and infants, breathing is irregular. Deep breathing is replaced by superficial. The 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). From the moment of birth, the same relationship between inhalation and exhalation as in adults is established: inhalation is shorter than exhalation.

Types of breathing. In a newborn, until the second half of the first year of life, the diaphragmatic type of breathing predominates, mainly due to contraction of the diaphragm muscles. Chest breathing is difficult because the chest has a pyramidal shape, the upper ribs, the manubrium of the sternum, the collarbone and the entire shoulder girdle are located high, the ribs lie almost horizontally, and the respiratory muscles of the chest are weak. From the moment the child begins to walk and increasingly takes a vertical position, breathing becomes abdominal. From 3-7 years of age, due to the development of the muscles of the shoulder girdle, the thoracic type of breathing begins to predominate over the diaphragmatic one. Gender differences in the type of breathing begin to emerge from 7-8 years of age and end by 14-17 years. By this time, girls develop thoracic breathing, and boys develop abdominal breathing.

Lung volumes in children. In a newborn baby, the volume of the lungs increases slightly during inspiration. The tidal volume is only 15-20 ml. During this period, the body is supplied with oxygen by increasing the respiratory rate. With age, along with a decrease in respiratory rate, tidal volume increases (Table 6.2). Minute volume of respiration (MVR) 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 MVR 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 it is 96 ml/min/kg). This is explained high level metabolism and consumption of 0 2 in children compared to adults. Thus, the oxygen requirement is (in ml/min/kg body weight): in newborns - 8-8.5; at 1-2 years - 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 capacity of the lungs in children of different ages(V.A. Doskin et al., 1997)

Table 6.2

Age	Vital capacity, ml	Volume, ml
		respiratory	reserve exhalation	reserve breath
Adults	4000-

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

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

Table 6.3

Increase in absolute indicators of all tidal volumes 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, an increase in strength respiratory muscles. Therefore, the energy cost of breathing decreases (Table 6.3).