Physiological features of breathing in children. Features of the respiratory system in newborns

Respiratory organs in a child differ significantly from the respiratory system of an adult. By the time of birth, the child’s respiratory system has not yet reached full development, therefore, in the absence of proper care, children experience an increased incidence of respiratory diseases. The largest number of these diseases occurs between the ages of 6 months and 2 years.

Studying the anatomical and physiological characteristics of the respiratory organs and conducting a wide range of preventive measures taking these features into account can contribute to a significant reduction in diseases respiratory tract, which are still one of the main causes of child mortality.

Nose the child is relatively small, the nasal passages are narrow. The mucous membrane lining them is tender, easily vulnerable, rich in blood and lymphatic vessels; this creates conditions for the development of an inflammatory reaction and swelling of the mucous membrane during infection of the upper respiratory tract.

Normally, a child breathes through his nose; he cannot breathe through his mouth.

With age as development progresses upper jaw and the growth of facial bones, the length and width of the burrows increase.

The Eustachian tube, which connects the nasopharynx with the tympanic cavity of the ear, is relatively short and wide; it has a more horizontal direction than that of an adult. All this contributes to the introduction of infection from the nasopharynx into the middle ear cavity, which explains the frequency of its involvement in upper respiratory tract disease in a child.

The frontal sinus and maxillary cavities develop only by 2 years, but they reach their final development much later.

Larynx in children early age has a funnel shape. Its lumen is narrow, the cartilage is pliable, the mucous membrane is very tender, rich blood vessels. The glottis is narrow and short. These features explain the frequency and ease of narrowing of the glottis (stenosis), even with relatively moderate inflammation of the laryngeal mucosa, which leads to difficulty breathing.

Trachea and bronchi also have a narrower clearance; their mucous membrane is rich in blood vessels; when inflamed, it easily swells, which causes a narrowing of the lumen of the trachea and bronchi.

Lungs, an infant's lungs differ from the lungs of an adult in the weak development of elastic tissue, greater blood supply and less airiness. The weak development of elastic lung tissue and insufficient excursion of the chest explains the frequency of atelectasis (collapse of lung tissue) in infants, especially in the infero-posterior sections of the lungs, since these sections are poorly ventilated.

Lung growth and development occurs over a fairly long period of time. Lung growth is especially vigorous in the first 3 months of life. As the lungs develop, their structure changes: connective tissue layers are replaced by elastic tissue, the number of alveoli increases, which significantly increases the vital capacity of the lungs.

Thoracic cavity the child's is relatively small. The respiratory excursion of the lungs is limited not only because low mobility chest, but also due to the small size of the pleural cavity, which in a young child is very narrow, almost slit-like. Thus, the lungs almost completely fill the chest.

The mobility of the chest is also limited due to weakness of the respiratory muscles. The lungs expand mainly towards the pliable diaphragm, therefore, before walking, the type of breathing in children is diaphragmatic. With age, the respiratory excursion of the chest increases and a thoracic or abdominal type of breathing appears.

Age anatomical and morphological features chest cause some functional features breathing of children at different ages.

The oxygen requirement of a child during a period of intensive growth is very high due to increased metabolism. Since breathing in infants and young children is superficial, the high oxygen demand is covered by the respiratory rate.

Within a few hours after the newborn’s first breath, breathing becomes correct and fairly uniform; sometimes it is established only after a few days.

Number of respirations in a newborn up to 40-60 per minute, in a child of 6 months - 35-40, in 12 months - 30-35, in 5-6 years - 25, at the age of 15 years - 20, in an adult - 16.

The number of breaths should be counted when the child is calm, monitoring the respiratory movements of the chest or placing a hand on the stomach.

Vital capacity of the lungs the child's is relatively large. In school-age children, it is determined by spirometry. The child is asked to do deep breath and using a special device - a spirometer - measure the maximum amount of air exhaled after this ( table 6.) (according to N.A. Shalkova).

Table 6. Vital capacity of the lungs in children (in cm3)

With age vital capacity lungs increases. It also increases as a result of training, with physical work and playing sports.

Breathing is regulated by the respiratory center, which receives reflex irritations from the pulmonary branches vagus nerve. The excitability of the respiratory center is regulated by the cerebral cortex and the degree of blood saturation with carbon dioxide. With age, cortical regulation of breathing improves.

As the lungs and chest develop and the respiratory muscles strengthen, breathing becomes deeper and less frequent. By the age of 7-12, the breathing pattern and shape of the chest are almost no different from those of an adult.

The correct development of the child's chest, lungs and respiratory muscles depends on the conditions in which he grows. If a child lives in a stuffy room where people smoke, cook food, wash and dry clothes, or is in a stuffy, unventilated room, then conditions are created that disrupt the normal development of his chest and lungs.

To strengthen the child’s health and good development of the respiratory system, prevent respiratory diseases, it is necessary for the child to be on fresh air winter and summer. Outdoor games, sports and physical exercise are especially useful.

Exclusively important role in strengthening the health of children, it is necessary to take them out of the city, where it is possible to organize the children’s stay in the air for the whole day.

The rooms in which children are located must be thoroughly ventilated. In winter, you should open the windows or transoms several times a day according to the established procedure. In a room with central heating, if there are transoms, ventilation can be carried out very often without cooling it. IN warm time windows must be open 24 hours a day.

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 along pulmonary artery to the lungs from the right ventricle (Table 2).

table 2

Partial pressure of gases in inspired and alveolar air, arterial and venous blood (mmHg)

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 in 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 of the 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

This is due to two reasons. One of them, naturally, is the small mass 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

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

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 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 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

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

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.

breathing bronchial asthma hardening

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 in the first years of life is poor in cavernous tissue; 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. The 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 2 years of age 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 poor development adnexal cavities In the nose of 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 are not noticeable 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 lymphoid tissue and the 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 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 level IV cervical vertebra(in adults 1-1 12 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 cartilages of the larynx in children are tender, very pliable, the epiglottis is relatively narrow up to 12-13 years of age and 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 of the thyroid cartilage in boys 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 a cry, usually does not depend on inflammatory phenomena, but on the 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-JV 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; 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. The muscle layer of the membranous part of the tracheal wall is well developed even in newborns; elastic tissue is found in relatively small quantities.

A child's trachea is soft and easily compressed; under the influence of 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 the more frequent hits foreign bodies into the right bronchus. The bronchi are narrow, their cartilage is soft, muscle and elastic fibers are relatively poorly developed, the mucous membrane 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. Right lung, as a rule, 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 lobe of the right lung almost merges with the upper one. 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.

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

The volume of the lungs of already breathing newborns is 70 cm3, 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.

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 is 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. 49).

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 children 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 equal to 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 descends to the level of the 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 effects environment. Age-related anatomical features of the chest also determine some physiological characteristics breathing of children in different periods childhood.

The first breath of a newborn. During the period of intrauterine development in the fetus, gas exchange occurs exclusively due to the placental circulation. At the end of this period, the fetus develops regular intrauterine respiratory movements, indicating the ability of the respiratory center to respond 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 a lack of oxygen and carbon dioxide, the increased accumulation of which from the moment of cessation 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 so much an excess of carbon dioxide in the blood of a newborn, but mainly 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; The uneven breathing rhythm observed in some cases during the first hours and even days of a child’s life usually quickly levels out.

The respiratory rate in newborns is 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.

Children's age

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: 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 disruption of the correct respiratory rhythm.

On average, one respiratory movement in newborns accounts for 2"/2 -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 heart beats. contractions. These ratios are usually maintained when the pulse 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 equal on average to 20 cm3,y one month old baby it rises to approximately 25 cm3, by the end of the year reaches 80 cm3, by 5 years - about 150 cm3, by 12 years - on average about 250 cm3, and by 14-16 years it rises to 300-400 cm3; however, this value, apparently, can fluctuate within fairly wide individual limits, since the data of different authors differ 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 number of respiratory movements) quickly increases with age and is approximately equal to 800-900 cm3 in a newborn, 1400 cm3 in a child aged 1 month, and about 2600 cm3 by the end of the 1st year. , at the age of 5 years - about 3200 cm3 and at 12-15 years - about 5000 cm3.

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 the active participation of the 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 thoracoabdominal 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 predominates diaphragmatic breathing with minor participation of the costal muscles. In children infancy so-called thoracic-abdominal breathing with a predominance of diaphragmatic breathing is detected; excursions of the chest are weakly expressed in its upper parts and, conversely, much stronger in the lower departments 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 muscle development shoulder girdle is becoming more and more clear chest breathing, beginning to definitely dominate the diaphragmatic one.

The first differences in the type of breathing depending on gender begin to clearly appear at the age of 7-14 years; in prepubertal and pubertal periods boys develop mainly the abdominal type, and girls develop breast type breathing. Age-related changes breathing types 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 anterior-posterior and lateral dimensions of the chest increase.

Features of breathing regulation

As is known, the act of breathing is regulated by the respiratory center, whose activity is characterized by automaticity and rhythm. The respiratory center is located in the middle third of the medulla oblongata on either side of the midline. Excitation, rhythmically arising in the cells of the respiratory center, along centrifugal (efferent) nerve pathways transmitted to the respiratory muscles. Various irritations affecting the extero- and interoreceptors of the human body travel through centripetal pathways to the respiratory center and affect the processes of excitation and inhibition that occur in it; The role of impulses coming from the lungs themselves is especially great when irritating numerous receptors located in the bronchioles and alveoli;

the excitation that occurs during inhalation in these interoceptors is transmitted along the fibers of the vagus nerve to the respiratory center and inhibits its activity; the inhibited center does not send exciting impulses to the respiratory muscles, and they relax, and the exhalation phase begins; in a collapsed lung, the afferent endings of the vagus nerve are not excited, therefore, the inhibitory influence coming through its fibers is eliminated, the respiratory center is excited again, the resulting impulses are sent to the respiratory muscles and a new breath occurs; self-regulation occurs: inhalation causes exhalation, and the latter causes inhalation. Of course, the composition of the alveolar air also plays a role.

Consequently, the regulation of breathing in children is carried out mainly by the neuro-reflex pathway. Irritation of the endings of the centripetal nerves of the skin, muscles, vascular reflexogenic zones, endings of the sinocarotid nerve, etc., in the same reflex way, affects the rhythm and depth of breathing. The composition of the blood, the content of oxygen and carbon dioxide in it, the reaction of the blood, the accumulation of lactic acid or various pathological metabolic products in it also affect the function of the respiratory center; these irritations can be transmitted to it as a result of the influence of the blood composition on the receptors embedded in the walls of the vessels themselves, as well as as a result of the direct effect on the respiratory center of the composition of the blood washing it (humoral influence).

The function of the respiratory center of the medulla oblongata is constantly regulated by the cerebral cortex. The rhythm of breathing and its depth change under the influence of various emotional moments; an adult and older children can voluntarily change both the depth and frequency of breathing and can hold it for some time. Experiments on animals and observations in humans have proven the possibility of conditionally reflex influences for breathing. All this speaks to the regulatory role of the cerebral cortex. In very young children, it is often necessary to observe disturbances in the rhythm of breathing, even short-term complete cessation of breathing, for example in premature infants, which must be explained by the morphological immaturity of their central and peripheral nervous system and, in particular, the cerebral cortex. A slight disturbance in the rhythm of breathing during sleep and in older children must be explained by the unique relationship between the cortex and the subcortical region of the brain.

The regulatory role of the central nervous system ensures the integrity of the body and explains the dependence of breathing on the function of other organs - the circulatory system, digestion, blood system, metabolic processes, etc. The close dependence of the function of some organs on the function of others is especially clearly reflected in children with less perfect regulation of cortico-visceral connections.

Protective reflexes from the mucous membranes of the respiratory tract - sneezing and coughing - are expressed, although less clearly, already in children of the newborn period.

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. The 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 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, the accumulations of lymphoid tissue and tonsils hypertrophy somewhat, reaching maximum growth 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 of the thyroid cartilage in boys 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 a cry, usually does not depend on inflammatory phenomena, but on the 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. The muscle layer of 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; under the influence of 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 the more frequent entry of 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 lobe of the right lung almost merges with the upper one. 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.

The differentiation of individual cellular elements must be distinguished from the growth of lung mass. 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 of intrapulmonary connective tissue layers and an increase in 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 is 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 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 thoracic index (the percentage ratio between the anteroposterior and transverse diameters of the chest): in a fetus of the early embryonic period it is 185, in a newborn 90, by the end of the year - 80, by 8 years - 70, after puberty it is again slightly 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 years descends to the level of the 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 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 children’s breathing in different periods of childhood.

Newborn's first breath. During the period of intrauterine development in the fetus, gas exchange occurs exclusively due to the placental circulation. At the end of this period, the fetus develops regular intrauterine respiratory movements, indicating the ability of the respiratory center to respond 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 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 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 mother’s birth canal ends. 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; The uneven breathing rhythm observed in some cases during the first hours and even days of a child’s life usually quickly levels out.

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: 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 disruption of the correct respiratory rhythm.

On average, one respiratory movement in newborns accounts for 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 heart beats. 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 in a state of quiet sleep is on average 20 cm 3, in a one-month-old child it increases 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 different authors differ 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 the active participation of the 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 infants, so-called thoraco-abdominal breathing with a predominance of diaphragmatic breathing is detected; excursions of the chest are weakly expressed in its upper parts and, conversely, much stronger in the lower parts. As the child moves from a constant horizontal position to a vertical position, 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 develop mainly the abdominal type, and girls develop the thoracic type of breathing. Age-related changes in the type of breathing are predetermined by the above-mentioned anatomical features of the 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 later periods, when the ribs drop somewhat downwards and anteriorly and when they are raised, the anteroposterior and lateral dimensions of the chest increase.

Respiration is a complex physiological process that can be divided into three main stages: gas exchange between blood and atmospheric air (external respiration), gas transport, gas exchange between blood and tissues (tissue respiration).

External breathing– exchange of gases between external air and blood occurs only in the alveoli.

Pulmonary ventilation is the transfer of inhaled air through the airways to the zone of intra-alveolar diffusion.

Passing through the airways, the air is cleaned of impurities and dust, heated to body temperature, and moistened.

The space in the airways in which no gas exchange occurs was called dead or noxious space by Zuntz (1862). Young children have comparatively more dead space than adults.

Gas exchange in the lungs occurs due to the difference between the partial pressure of gases in the alveolar air and the tension of gases in the blood of the pulmonary capillaries.

The rate of diffusion is directly proportional to the force that ensures the movement of gas, and inversely proportional to the amount of diffusion resistance, that is, the obstacle that occurs in the path of gas molecules moving through the airborne barrier. Gas diffusion worsens with a decrease in the gas exchange surface of the lung and with an increase in the thickness of the airborne barrier.

Inhaled atmospheric air contains 79.4% nitrogen and inert gases (argon, neon, helium), 20.93% oxygen, 0.03% carbon dioxide.

In the alveoli, the inhaled air mixes with the air present there, acquires 100% relative humidity, and the alveolar air in an adult already has the following gas content: O 2 - 13.5–13.7%; CO 2 – 5–6%; nitrogen – 80%. At this percentage of oxygen and a total pressure of 1 atm. The partial pressure of oxygen is approximately 100–110 mmHg. Art., the oxygen tension in the venous blood flowing into the lung is 60–75 mm Hg. Art. The resulting pressure difference is sufficient to ensure the diffusion into the blood of about 6 liters of oxygen per minute; this amount of oxygen is sufficient to ensure heavy muscular work.

The partial pressure of carbon dioxide (CO 2) in the alveolar air is 37–40 mm Hg. Art., and the CO 2 tension in the venous blood of the pulmonary capillaries at rest is 46 mm Hg. Art. The physicochemical properties of the alveolar membrane are such that the solubility of oxygen in it is 0.024, and CO 2 - 0.567, therefore, carbon dioxide diffuses through the alveolar-capillary membrane 20–25 times faster than oxygen, and a pressure difference of 6 mm ensures removal CO 2 leaves the body during the heaviest muscular work.

Exhaled air is a mixture of alveolar and atmospheric air present in the airways. It contains in adults: O 2 – 15–18% (16.4); CO 2 – 2.5–5.5% (4.1).

By the difference in the O 2 content in inhaled and exhaled air, one can judge the utilization of O 2 by the lungs. Oxygen utilization in the lungs in adults is 4.5 vol%; in infants it is reduced and amounts to 2.6–3.0 vol% oxygen; with age, the percentage of oxygen utilization increases to 3.3–3.9 vol%.

This is due to the fact that infant breathes more frequently and more shallowly. The less often and deeper the breathing, the better the oxygen in the lungs is used, and vice versa.

When you breathe, water is removed from the body, as well as some quickly evaporating substances (for example, alcohol).

The respiratory cycle consists of inhalation and exhalation.

Inhale is carried out due to contraction of the respiratory muscles, while the volume of the chest increases, the alveoli expand, and negative pressure arises in them. As long as there is a pressure difference between the alveoli and the atmosphere, air enters the lungs.

At the moment of transition from the inhalation phase to the exhalation phase, the alveolar pressure is equal to atmospheric pressure.

Exhalation is carried out mainly due to the elasticity of the lungs. The respiratory muscles relax, and pressure caused by elastic traction of the lungs begins to act on the air in the lungs.

The regulation of the act of breathing is carried out through the neurohumoral pathway.

The respiratory center is located in the medulla oblongata. It has its own automatism, but this automatism is not as pronounced as the automatism of the heart; it is under the constant influence of impulses coming from the cerebral cortex and from the periphery.

The rhythm, frequency and depth of breathing can be arbitrarily changed, of course, within certain limits.

For the regulation of breathing, changes in CO 2 , O 2 and pH voltages in the body are of great importance. An increase in CO 2 tension in the blood and tissues, a decrease in O 2 tension causes an increase in the volume of ventilation, a decrease in CO 2 tension, an increase in O 2 tension is accompanied by a decrease in the volume of ventilation. These changes in breathing occur as a result of impulses entering the respiratory center from chemoreceptors located in the carotid and aortic sinuses, as well as in the respiratory center medulla oblongata.

To characterize the functions of external respiration, an assessment of lung volumes, pulmonary ventilation, ventilation-perfusion ratio, blood gases and ABS (acid-base status) is used (Table 23).

Table 23

Respiratory frequency in children [Tur A.F., 1955]

At rest, a healthy adult makes 12–18 breathing movements per minute.

There are 2.5–3 heartbeats per breath in a newborn, and 3.5–4 in older children.

The breathing rhythm in children in the first months of life is unstable.

Tidal volume (VT). The lungs of each person have a certain minimum (on exhalation) and maximum (on inhalation) internal volume. During the breathing process, changes occur periodically depending on the nature of breathing. During quiet breathing, changes in volume are minimal and, depending on body weight and age, amount to 250–500 ml.

The breathing volume in newborns is about 20 ml, by one year – 70–60 ml, by 10 years – 250 ml.

Minute respiration volume (MRV)(breathing volume multiplied by the number of breaths per minute) increases with age. This indicator characterizes the degree of ventilation of the lungs.

Maximum ventilation (MVV)- the volume of air entering the lungs in 1 minute during forced breathing.

Forced expiratory volume (FEV 1)- the volume of air exhaled in the first second, at the maximum possible exhalation rate. A decrease in FEV 1 to 70% VC or less indicates the presence of obstruction.

Maximum speed of inhalation and exhalation (MS ind, MS ext) characterizes bronchial patency. IN normal conditions MS vd of an adult is from 4–8 to 12 l/s. In case of violation bronchial obstruction it decreases to 1 l/s or less.

Dead respiratory space (DRS) includes part of the airway space that does not participate in gas exchange (oral cavity, nose, pharynx, larynx, trachea, bronchi), and part of the alveoli, the air in which does not participate in gas exchange.

Alveolar ventilation (AV) is determined by the formula:

AB = (DO – MDP) × BH.

In healthy people, AV accounts for 70–80% of total pulmonary ventilation.

Total oxygen consumption. At rest, an adult consumes approximately 0.2 liters of oxygen per minute. During work, oxygen consumption increases in proportion to energy consumption up to a certain limit, which, depending on the individual characteristics of the body, can exceed the level of basal metabolism by 10–20 or more times.

Maximum oxygen consumption– the volume of oxygen consumed by the body in 1 minute with extremely forced breathing.

Respiratory coefficient (RK)– the ratio of the volumes of carbon dioxide released and oxygen consumed.

Respiratory equivalent (RE)- this is the volume of inhaled air required for the lungs to absorb 100 ml of oxygen (that is, this is the number of liters of air that must be ventilated through the lungs in order to use 100 ml of O 2).

Lung volumes include:

TLC (total lung capacity) - the volume of gas contained in the lungs after maximum inspiration;

Vital capacity (vital capacity of the lungs) - the maximum volume of gas exhaled after maximum inspiration;

RLV (residual lung volume) - the volume of gas remaining in the lungs after maximum exhalation;

FRC (functional residual capacity) - the volume of gas in the lungs after a quiet exhalation;

RO inspiratory reserve volume - the maximum volume of gas that can be inhaled from the level of a quiet inspiration;

RO exhalation (expiratory reserve volume) – the maximum volume of gas that can be exhaled after a quiet exhalation;

EB (inspiratory capacity) – the maximum volume of gas that can be inhaled from the level of quiet exhalation;

DO (tidal volume) - the volume of gas inhaled or exhaled in one respiratory cycle.

VC, EB, PO ind, PO out, DO are measured using a spirograph.

TEL, FRC, TOL are measured by the gel dilution method in a closed system.

The results of the study of lung volumes are assessed by comparison with the proper values ​​calculated using regression equations reflecting the relationship of volumes with the growth of children, or using nomograms.

Using vital capacity, you can assess the ventilation capacity of the lungs as a whole. Vital capacity decreases under the influence of many factors - both pulmonary (with airway obstruction, atelectasis, pneumonia, etc.) and extrapulmonary (with a high diaphragm, decreased muscle tone).

A decrease in vital capacity by more than 20% of the expected value is considered pathological.

Forced vital capacity (FVC)– the volume of air exhaled as quickly and completely as possible after a full deep breath. In healthy people, FVC is usually greater than VC by 100–200 ml due to the fact that greater effort promotes a more complete exhalation. FVC is a functional load to detect changes in the mechanical properties of the ventilation device. In patients with airway obstruction, FVC is less than VC.

To assess bronchial patency, the Tifno test is used - the ratio of the forced expiratory volume in 1 s (FEV 1) to the entire forced expiratory volume of VC (FVC), expressed as a percentage. 75% is normal. Values ​​below 70% indicate airway obstruction, and values ​​above 85% indicate the presence of restrictive phenomena.

Peak expiratory flow rate (PEF) is used to determine the presence and measurement of airway obstruction. For this purpose, mini-peak flow meters (peak flow meters) are used. The most convenient and accurate is a mini-Wright counter.

The person being examined takes a maximally deep breath (up to the value of vital capacity), and then exhales short and sharply into the apparatus. The obtained result is assessed by comparison with the nomogram data. Measuring the peak expiratory flow rate using a Wright peak flow meter at home makes it possible to objectively assess the patient's response to the treatment used.

Transport of oxygen from lungs to tissues. Oxygen, having passed through the alveolar-capillary membrane, dissolves in the blood plasma according to physical laws. At normal temperature body, 0.3 ml of oxygen is dissolved in 100 ml of plasma.

Hemoglobin plays the main role in the transport of oxygen from the lungs to the tissues. 94% of oxygen is transported in the form of oxyhemoglobin (HbO 2). 1 g of Hb binds 1.34–1.36 ml of O 2.

Blood oxygen capacity (BOC)- the maximum amount of oxygen that can be bound by hemoglobin in the blood after it is completely saturated with oxygen. When hemoglobin is completely saturated with oxygen, 1 liter of blood can contain up to 200 ml of oxygen. The normal KEK value for an adult is 18–22% by volume. The KEK of a newborn is equal to or slightly higher than the KEK of an adult. Soon after birth, it decreases, reaching a minimum value at the age of 1–4 years, after which it gradually increases, reaching adult levels at puberty.

The chemical bond of oxygen with hemoglobin is reversible. In tissues, oxyhemoglobin releases oxygen and turns into reduced hemoglobin. Oxygenation of hemoglobin in the lungs and its restoration in tissues is determined by the difference in the partial pressure of oxygen: the alveolar-capillary pressure gradient in the lungs and the capillary-tissue gradient in the tissues.

Transport of carbon dioxide formed in the cells to the place of its removal - the pulmonary capillaries - is carried out in three forms: carbon dioxide, entering the blood from the cells, dissolves in it, as a result of which its partial pressure in the blood increases. Carbon dioxide physically soluble in plasma accounts for 5–6% of its total volume transported by blood. 15% of carbon dioxide is transported in the form of carbohemoglobin, more than 70–80% of endogenous carbon dioxide is bound by blood bicarbonates. This connection plays a large role in maintaining acid-base balance.

Tissue (internal) respiration– the process of tissue absorption of oxygen and release of carbon dioxide. In a broader sense, these are the enzymatic processes of biological oxidation occurring in each cell, as a result of which molecules fatty acids, amino acids, carbohydrates are broken down into carbon dioxide and water, and the energy released during this process is used and stored by the cell.

In addition to gas exchange, the lungs also perform other functions in the body: metabolic, thermoregulatory, secretory, excretory, barrier, cleansing, absorption, etc.

The metabolic function of the lungs includes lipid metabolism, the synthesis of fatty acids and acetone, the synthesis of prostaglandins, the production of surfactant, etc. The secretory function of the lungs is realized due to the presence of specialized glands and secretory cells that secrete serous-mucosal secretion, which, moving from the lower to the upper sections, moisturizes and protects the surface of the respiratory tract.

The secretion also contains lactoferin, lysozyme, whey proteins, antibodies - substances that have antimicrobial effect and promoting lung rehabilitation.

excretory lung function manifests itself in the release of volatile metabolites and exogenous substances: acetone, ammonia, etc. The absorption function is due to the high permeability of the alveolar-capillary membranes for fat- and water-soluble substances: ether, chloroform, etc. The inhalation route of administration is used for a number of drugs.