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 air-hematic barrier. Gas diffusion worsens as gas exchange rate decreases lung surface 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 general pressure at 1 atm. The partial pressure of oxygen is approximately 100–110 mmHg. Art., the tension of oxygen in flowing into the lung venous blood is 60–75 mmHg. 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. Physico-chemical properties the alveolar membrane is such that the solubility of oxygen in it is 0.024, and CO 2 is 0.567, therefore, through the alveolar-capillary membrane, carbon dioxide diffuses 20–25 times faster than oxygen, and a pressure difference of 6 mm ensures the removal of CO 2 from 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 children infancy 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 breathing, the better oxygen is used in the lungs, 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 increases chest, 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 by 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.
To regulate breathing great value has a change in CO 2 , O 2 and pH voltages in the body. 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 of the medulla oblongata itself.
To characterize the functions 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. Under normal conditions, the MR of an adult human ranges 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.
U healthy people AV accounts for 70–80% of total 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) 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 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 obstruction respiratory tract 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 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) – maximum quantity oxygen, which 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 caused 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 alveolar-capillary membranes for fat- and water-soluble substances: ether, chloroform, etc. Inhalation route administration is used for a number of drugs.
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. Largest number These diseases occur between the ages of 6 months and 2 years.
Studying the anatomical and physiological characteristics of the respiratory system and carrying out a wide range of preventive measures taking into account these characteristics can contribute to a significant reduction in respiratory diseases, 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.
Frontal sinus and the maxillary cavities develop only by 2 years, but they reach their final development much later.
Larynx in young children it 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, infant differ from the lungs of an adult in the weak development of elastic tissue, greater blood supply and less airiness. Poor 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 lower 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 due to the low mobility of the chest, but also due to its small size 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-related anatomical and morphological features of the chest determine some functional features of the breathing of children at different age periods.
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 take a deep breath and using a special device - a spirometer - the maximum amount of air exhaled after this is measured ( table 6.) (according to N.A. Shalkova).
Table 6. Vital capacity of the lungs in children (in cm3)
|
Age |
Boys |
Limits |
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With age, the vital capacity of the 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 stimuli from the pulmonary branches of the 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.
Proper development of the chest, lungs and respiratory muscles a child depends on the conditions in which he grows up. 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 violate normal development his chest and lungs.
To improve the child's health and good development respiratory organs, to prevent respiratory diseases, it is necessary for the child to remain on the fresh air winter and summer. Outdoor games, sports and physical exercise are especially useful.
Taking them out of the city, where it is possible to organize children’s stay in the air for the whole day, plays an extremely important role in strengthening the health of children.
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. During the warm season, windows should be open around the clock.
Surely every mother will remember such an episode from her life: she is bending over her child’s crib. She looks at him and can’t get enough of him. He looks, strokes and listens to his breathing. Breathing of a newborn.
This process is so natural for an adult that he doesn’t even think about how he does it. Only when he gets sick. But for a little man who has just been born, the way he breathes has important. After all, first of all, it will depend on how often he will suffer from respiratory diseases.
Children's doctors also claim that the development of his speech will depend on how correctly he inhales and exhales. Therefore, parents should not ignore everything related to baby’s breathing if they want their baby to grow up healthy.
These organs are usually considered to be among the most important ones that ensure the vital activity of the human, in our case, the child’s body. His work is divided into two stages:
Although the respiratory organs of a child have a similar structure to similar organs in adults, they also have some features that disappear in adulthood. These differences, on the one hand, are very important, since they provide the necessary mode of operation of the child’s respiratory system, and on the other hand, they are also the cause of minor complications characteristic of infancy.
The underdevelopment of the infant's respiratory system is the reason that his breathing itself is jerky, with a frequently changing pace. Usually this looks like short breaths followed by one deep breath of long duration. This baby breathing has its own name - “Cheyne-Stokes breathing” and is absolutely normal for a newborn, especially if he was born ahead of schedule. This leveling of breathing usually occurs by the end of the first month of life, and by the age of one, the breathing rate becomes similar to that of an adult.
If the infant’s breathing rate differs from that described above, then this is a reason to consult a doctor.
Dissimilarity respiratory system an adult and a child is that the latter’s nose and nasopharynx are much shorter and narrower. This makes it almost impossible for the little person to take a full, deep breath.
During the first months of life, a baby is characterized by so-called abdominal breathing. Of course, over time he will also master the chest, and then learn to combine these two types. By the way, doctors all over the world agree on one thing - combined breathing is the most useful and productive for humans.
Parents need to closely monitor their baby's breathing. This is precisely the case when excessive suspiciousness of parents can play to the benefit of the child. So, any disturbance in the rhythm or its frequency can signal a disorder child's body.
First signs respiratory disorders usually occur while the mother and newborn are in the maternity hospital. But there shouldn’t be much concern here, since there are doctors nearby and they will quickly provide assistance. necessary help. But at home you will have to try. Any breathing problems should be discussed with your pediatrician.
Preventive measures
There are also conditions in which there is nothing particularly bad for the child, but it is imperative to notify the doctor about them:
There are several other points that cause fear among parents. But at the same time, these are quite normal phenomena for this age:
Many parents wonder: how to find out if their baby is breathing correctly, so as not to worry in vain.
First you need to find out the frequency of his breathing. The procedure is quite easy. Naturally, there are some requirements - the baby must be healthy at this moment, and during the procedure must be in a relaxed state. You also need to make sure you have a stopwatch; it will help you find out the number of breaths per minute and compare the indicator with the standard ones. And they are as follows:
A slight deviation in one direction or another should not cause concern to parents. But if the deviation is quite significant, for example, for the third age group The breathing rate exceeds 35 breaths, which is a cause for concern. After all, such a child’s breathing means that it is superficial. This means that it is not suitable for complete ventilation of the lungs.
This causes frequent respiratory diseases in the child, so it is necessary to find out the cause of such breathing and eliminate it.
To do this, there are several exercises from the children's yoga complex. The first exercise begins with the child needing to take the so-called lion (sphinx) pose - he should lie on his stomach with his legs extended. Upper part the body rises with emphasis on the hands. In this position, he should take a breath, hold his breath for a couple of seconds and quickly exhale. The benefit of the exercise is that in this position the chest opens most fully. One of the adults can count to three.
The second exercise is designed to teach abdominal breathing. The baby should be placed on his back, on a flat surface. He should place his hands under his head and bend his knees slightly. There should be 10-15 repetitions in one approach. Along with learning to breathe, the abdominal muscles are strengthened.
As you understand, a child will be able to perform these exercises at the age of no earlier than
2-3 years. For now, you just need to monitor your baby’s breathing.
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. Although the maxillary cavity is already present in newborns, it 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 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; 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 level IV cervical vertebra(in adults 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 cartilages of the larynx in children are tender, 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. Tracheal bifurcation in newborns corresponds to III-IV thoracic vertebrae, in children 5 years old - IV-V and 12 year olds - V - VI vertebrae.
The growth of the trachea is approximately parallel to the growth of the trunk; 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 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 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.
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. Children's lung poor 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 in respiratory bronchioles, the development of alveoli from 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. Overall growth 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 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 underdevelopment elastic fabric.
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.
Lymph nodes. The following groups are distinguished: 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 anterior-posterior and lateral diameters of the chest are almost equal, and epigastric angle- very stupid.
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 a 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 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 effects. environment. Age-related anatomical features of the chest also determine some physiological characteristics breathing of children in different periods of childhood.
Newborn's first breath. During 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 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 correct and mostly fairly uniform breathing is established; 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, 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 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 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 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 lower sections. 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, 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; During the prepubertal and pubertal periods, boys develop mainly the abdominal type, and girls develop the thoracic type of 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.
The respiratory tract is divided into three sections: upper (nose, pharynx), middle (larynx, trachea, bronchi), lower (bronchioles, alveoli). By the time the child is born, their morphological structure is still imperfect, which is also associated with the functional characteristics of breathing. F Formation of the respiratory system ends on average before the age of 7, and then only their sizes increase. All airways in children are significantly smaller and have a narrower lumen than in adults. The mucous membrane is thinner, more delicate, and easily damaged. The glands are underdeveloped, the production of IgA and surfactant is insignificant. The submucosal layer is loose, contains a small amount of elastic and connective tissue elements, many are vascularized. The cartilaginous framework of the respiratory tract is soft and pliable. This helps to reduce the barrier function of the mucous membrane, easier penetration of infectious and atopic agents into the bloodstream, and the emergence of preconditions for narrowing of the airways due to edema.
Another feature of the respiratory organs in children is that in young children they are small in size. The nasal passages are narrow, the shells are thick (the lower ones develop until the age of 4), so even minor hyperemia and swelling of the mucous membrane predetermine obstruction of the nasal passages, cause shortness of breath, and make sucking difficult. WITH paranasal sinuses By the time of birth, only the maxillary muscles are formed (develop up to 7 years of life). The ethmoidal, sphenoidal and two frontal sinuses complete their development before the ages of 12, 15 and 20 years, respectively.
The nasolacrimal duct is short, located close to the corner of the eye, its valves are underdeveloped, so the infection easily penetrates from the nose into the conjunctival sac.
The pharynx is relatively wide and small. The Eustachian (auditory) tubes connecting the nasopharynx and the tympanic cavity are short, wide, straight and located horizontally, which facilitates the penetration of infection from the nose to the middle ear. In the pharynx there is the Waldeer-Pirogov lymphoid ring, which includes 6 tonsils: 2 palatine, 2 tubal, 1 nasopharyngeal and 1 lingual. When examining the oropharynx, the term “pharynx” is used. Zev is anatomical education, surrounded at the bottom by the root of the tongue, on the sides - palatine tonsils and brackets, above - the soft palate and uvula, behind - back wall oropharynx, in front - the oral cavity.
The epiglottis in newborns is relatively short and wide, which may cause a functional narrowing of the entrance to the larynx and the occurrence of stridor breathing.
The larynx in children is located higher and longer than in adults, has a funnel-shaped shape with a clear narrowing in the subglottic space (4 mm in a newborn), which gradually expands (at 14 years of age up to 1 cm). The glottis is narrow, its muscles get tired easily. Vocal cords thick, short, mucous membrane very tender, loose, significantly vascularized, rich lymphoid tissue, easily leads to swelling of the submucosal membrane when respiratory infection and the occurrence of croup syndrome.
Trachea relative longer length and width, funnel-shaped, contains 15-20 cartilaginous rings, very mobile. The walls of the trachea are soft and collapse easily. The mucous membrane is tender, dry, and well vascularized.
Formed by the time of birth. The size of the bronchi increases rapidly in the 1st year of life and during adolescence. they are also formed by cartilaginous semirings, which in early childhood do not have endplates connected by a fibrous membrane. The cartilage of the bronchi is very elastic, soft, and moves easily. The bronchi in children are relatively wide, the right main bronchus is almost a direct continuation of the trachea, so it is in it that foreign objects often end up. The smallest bronchi are characterized by absolute narrowness, which explains the occurrence of obstructive syndrome in young children. The mucous membrane of the large bronchi is covered with ciliated epithelium, which performs the function of cleansing the bronchi (mucociliary clearance). Incomplete myelination of the vagus nerve and underdevelopment of the respiratory muscles contribute to the absence of a cough reflex in young children or a very weak cough impulse. Mucus accumulated in small bronchi easily clogs them and leads to atelectasis and infection of the lung tissue.
Lungs in children, as in adults, have a segmental structure. The segments are separated from each other by thin connective tissue partitions. The main structural unit of the lung is the acinus, but its terminal bronchioles end not in a brush of alveoli, as in adults, but in a sac (sacculus), with the “lace” edges of which new alveoli are gradually formed, the number of which in newborns is 3 times less than in adults. With age, the diameter of each alveoli increases. At the same time, the vital capacity of the lungs increases. The interstitial tissue of the lungs is loose, rich in blood vessels, fiber, and contains little connective tissue and elastic fibers. In this regard, the lung tissue in children in the first years of life is more saturated with blood and less airy. Underdevelopment of the elastic framework leads to emphysema and atelectasis. The tendency to atelectasis also arises due to a deficiency of surfactant - a film that regulates surface alveolar tension and stabilizes the volume of terminal air spaces, i.e. alveoli Surfactant is synthesized by type II alveolocytes and appears in a fetus weighing at least 500-1000 g. The younger the child’s gestational age, the greater the surfactant deficiency. It is the surfactant deficiency that forms the basis for insufficient expansion of the lungs in premature infants and the occurrence of respiratory distress syndrome.
The main functional physiological features of the respiratory organs in children are as follows. Children's breathing is frequent (which compensates for the small volume of breathing) and shallow. The higher the frequency younger child(physiological shortness of breath). A newborn breathes 40-50 times per minute, child aged 1 year - 35-30 times in 1 minute, 3 years old - 30-26 times in 1 minute, 7 years old - 20-25 times in 1 minute, 12 years old - 18-20 times in 1 minute, adults — 12-14 times in 1 minute. An acceleration or deceleration of breathing is noted when the respiratory rate deviates from the average by 30-40% or more. In newborns, breathing is irregular with short stops (apnea). The diaphragmatic type of breathing predominates, from 1-2 years of age it is mixed, from 7-8 years of age - in girls - thoracic, in boys - abdominal. The younger the child, the smaller the tidal volume of the lungs. Minute breathing volume also increases with age. However, this indicator relative to body weight in newborns is 2-3 times higher than in adults. The vital capacity of the lungs in children is significantly lower than in adults. Gas exchange in children is more intense due to the rich vascularization of the lungs, high blood circulation speed, and high diffusion capabilities.
