Anatomical and physiological features of the respiratory system in young children. Features of breathing in children and adolescents

The structure of the respiratory system in children during the neonatal period creates numerous preconditions for acute respiratory diseases. Therefore, the baby should be protected from exposure to infectious factors. We also suggest learning about all the structural features of the respiratory system in children in order to have a general idea of ​​how the gradual development of the nose and paranasal sinuses, throat and larynx, bronchi and lungs occurs.

According to medical statistics, respiratory diseases are much more common in children than in adults. This is due to the age-related characteristics of the structure of the respiratory system and the uniqueness of the protective reactions of the child’s body.

Along their length, the respiratory tract is divided into upper (from the opening of the nose to the vocal cords) and lower (larynx, trachea, bronchi), as well as lungs.

The main function of the respiratory system is to provide oxygen to the body tissues and remove carbon dioxide.

The process of formation of the respiratory organs in most children is completed by the age of 7, and in subsequent years their size only increases.

All airways in a child are much smaller and have narrower openings than in an adult.

The mucous membrane is thin, tender, vulnerable, dry, since the glands in it are poorly developed and little secretory immunoglobulin A (IgA) is produced.

This, as well as the rich blood supply, softness and pliability of the cartilaginous framework of the respiratory tract, and the low content of elastic tissue contribute to a decrease in the barrier function of the mucous membrane, the fairly rapid penetration of pathogenic microorganisms into the bloodstream, and create a predisposition to narrowing of the respiratory tract as a result of rapidly occurring swelling or compression of the pliable respiratory tract tubes from outside.

Features of the structure of the nose and paranasal sinuses in a child (with photo)

The structural features of the nose in children are primarily its small size, which causes a shortening of the path for the passage of air masses. A young child's nose is relatively small. The structure of a child's nose is such that the nasal passages are narrow, the lower nasal passage is formed only by the age of 4, which contributes to the occurrence of frequent runny nose (rhinitis). The nasal mucosa is very delicate and contains many small blood vessels, so even slight inflammation causes it to swell and further narrow the nasal passages. This leads to impaired nasal breathing in the child. The baby begins to breathe through his mouth. Cold air does not warm up and is not cleaned in the nasal cavity, but directly enters the bronchi and lungs, which leads to infection. It is no coincidence that many lung diseases in children begin with a “harmless” runny nose.

Children from an early age need to be taught proper breathing through their nose!

At birth, only the maxillary (maxillary) sinuses are formed in the child, so sinusitis can develop in young children. All sinuses develop completely by the age of 12 - 15 years. The structure of a child's nose and sinuses is constantly changing as the bones of the facial skull grow and form. The frontal and main paranasal sinuses gradually appear. The ethmoid bone with its labyrinth is formed throughout the first year of life.

Look at the structure of a child’s nose in the photo, which shows the main anatomical processes of development during the first year of life:

The structure of the throat and larynx in a child (with photo)

Continues the nasal cavity of the pharynx. The structure of a child’s throat provides reliable immune protection against the invasion of viruses and bacteria: it contains an important formation - the pharyngeal lymphatic ring, which performs a protective barrier function. The basis of the lymphopharyngeal ring is the tonsils and adenoids.

By the end of the first year, the lymphoid tissue of the pharyngeal lymphatic ring often hyperplasias (grows), especially in children with allergic diathesis, as a result of which the barrier function decreases. The overgrown tissue of the tonsils and adenoids is populated by viruses and microorganisms, and chronic foci of infection are formed (adenoiditis, chronic tonsillitis). Frequent ARVI cases are observed. In the case of severe adenoiditis, long-term disruption of nasal breathing contributes to changes in the facial skeleton and the formation of an “adenoid face.”

The larynx is located in the front upper part of the neck. Compared to adults, the larynx in children is short, funnel-shaped, has delicate, pliable cartilage and thin muscles. In the area of ​​the subglottic space there is a distinct narrowing, where the diameter of the larynx increases very slowly with age and is 6 - 7 mm at 5 - 7 years old, 1 cm by 14 years old. In the subglottic space there is a large number of nerve receptors and blood vessels, so it develops easily swelling of the submucosal layer. This condition is accompanied by severe breathing problems (larynx stenosis, false croup) even with minor manifestations of respiratory infection.

Look at the structure of the child’s throat and larynx in the photo, where the most important structural parts are highlighted and labeled:

Features of the structure and development of the bronchi and lungs in children

The continuation of the larynx is the trachea. The trachea of ​​an infant is very mobile, which, in combination with the softness of the cartilage, sometimes causes a slit-like collapse during exhalation and is accompanied by the appearance of expiratory shortness of breath or rough snoring breathing (congenital stridor). Symptoms of stridor usually disappear by 2 years of age. In the chest, the trachea divides into two large bronchi.

The characteristics of the bronchi in children lead to the development of frequent colds, which can develop into. Considering the structure of the bronchi in children, it is clear that their size in newborns is relatively small, which causes partial blockage of the bronchial lumen with mucus in cases of bronchitis. The main functional feature of the bronchi small child- insufficiency of drainage and cleaning functions.

The bronchi of babies are very sensitive to the effects of harmful environmental factors. Too cold or hot air, high air humidity, gas pollution, and dust lead to stagnation of mucus in the bronchi and the development of bronchitis.

Externally, the bronchi look like a branched tree, turned upside down. The smallest bronchi (bronchioles) end in small vesicles (alveoli) that make up the lung tissue itself.

The structure of the lungs in children is constantly changing, since they are constantly growing in the child. In the first years of a child’s life, the lung tissue is full of blood and lacks air. The process of gas exchange, vital for the body, occurs in the alveoli. Carbon dioxide from the blood passes into the lumen of the alveoli and is released into the external environment through the bronchi. At the same time, atmospheric oxygen enters the alveoli and then into the blood. The slightest disturbance in gas exchange in the lungs due to inflammatory processes causes the development of respiratory failure.

The chest is surrounded on all sides by muscles that provide breathing (respiratory muscles). The main ones are the intercostal muscles and the diaphragm. During inhalation, the respiratory muscles contract, which leads to expansion of the chest and an increase in the volume of the lungs due to their expansion. The lungs seem to suck in air from the outside. During exhalation, which occurs without muscular effort, the volume of the chest and lungs decreases, and air comes out. The development of the lungs in children inevitably leads to a significant increase in the vital volume of these important organs.

The child’s respiratory system reaches completeness in its structure by 8–12 years, but the formation of its function continues until 14–16 years.

In childhood, it is necessary to highlight a number of functional features of the respiratory system.

• The younger the child, the higher the respiratory rate. Increasing breathing compensates for the small volume of each respiratory movement and provides oxygen to the child’s body. At the age of 1-2 years, the number of breaths per minute is 30-35, at 5-6 years old - 25, at 10-15 years old - 18-20.
• The child's breathing is more shallow and arrhythmic. Emotional and physical stress increase the severity of functional respiratory arrhythmia.
• Gas exchange in children occurs more intensively than in adults, due to the rich blood supply to the lungs, blood flow speed, and high diffusion of gases. At the same time, the function of external respiration can easily be impaired due to insufficient lung excursions and straightening of the alveoli.

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Providing the body with oxygen is one of the most important functions of any living organism. The respiratory system of a child's body has its advantages, but there are also disadvantages.

The anatomical and physiological characteristics of a newborn are not perfect. The respiratory organs are very thin and loose.

The lungs of children have fewer lumens than those of an adult. A child's respiratory system develops during the first 7 years and becomes the same as that of an adult. Afterwards, it only increases in size as the child grows.

The function of respiration is to enrich the body's cells with oxygen.

The respiratory organs of the human body consist of the nasal cavity, pharynx, larynx, trachea, bronchi and lungs. Air enters the nasopharynx through the nostrils. Here, with the help of mucus and a large number of glands, the air is moistened and warmed. Nasopharyngeal mucus cleanses the air of dust, germs and other harmful substances.

Air enters the lungs through the larynx and trachea. When you inhale, air enters the lungs and air exchange occurs through the alveoli. Oxygen enters the pulmonary system, and at the same time carbon dioxide is removed during exhalation.

The alveoli are closely adjacent to the capillary cells, and when inhaling, oxygen easily passes into the pulmonary capillaries. From the capillaries, oxygenated blood enters the pulmonary veins and enters the left heart chamber. From there it is transferred to all organs of the human body.

Through capillaries located in various organs of the body, “exhaust” air with carbon dioxide enters the venous system. Next, through the right heart valve, blood with carbon dioxide enters the lungs. Well, then, as mentioned above, exhale.

The air supply in the lungs is enough for 5-6 minutes. A child's respiratory system is much smaller than an adult's, so breathing occurs much more frequently. A child can take up to 60 breaths in a minute.

To clean the air entering the body, it must pass through the glands and mucous membrane located in the nose. Only here, with the help of mucus and leukocytes, air disinfection occurs. When you exhale, all dust particles and germs leave the body. This is how the body's defense system is built. Therefore, it is very important to always breathe through your nose (especially on the street or in public places).

Features of the structure of the respiratory system organs in children

The anatomical and physiological features differ from the structure of the adult respiratory system. In children they are characterized by:

• narrow clearance;
• short stroke length;
• the presence of vascular vessels in the mucosa;
• the delicate membrane of the lining tissues of the respiratory system;
• loose lymph tissues.

The respiratory system is susceptible to greater penetration of microbes into the body. Because of this, children often suffer from respiratory diseases. With age, physiological features disappear. The system becomes more resistant to the environment in which the child’s body is located.

In a child, it consists of the airways and respiratory department. The latter represents the lungs themselves. The respiratory tract, in turn, is divided into upper and lower.

Upper paths

The upper respiratory tract of a child consists of the nose, nasopharyngeal space and cavity, nasal canal and pharynx. The system of upper pathways is still poorly developed, unable to repel infectious penetrations and fight foci of diseases. It is because of poor development that the child is exposed to frequent diseases: acute respiratory viral infections, acute respiratory infections, influenza.

The nasal passages are short and narrow. Even the smallest swelling can affect the quality of breathing through the upper respiratory tract. This structure in young children is due to the characteristics of the facial skeleton. During the same period of child development, the nasal sinuses are already developed, but only two: the upper and middle. The lower sinus will form during the first 4 years of the baby's life.

The lining of the sinuses has a large number of blood vessels. Any damage to the mucous membrane, which is rich in blood vessels, can lead to injury. Until the age of 9 years, a child does not have nosebleeds due to undeveloped cavernous tissue. If similar phenomena are observed in a baby, then the child may have pathologies of a different nature. In infancy, only the maxillary sinuses are developed in the child; There is no main sinus yet.

The frontal and ethmoid will have their usual appearance only by 2 years of age. This structure of the baby’s nasal sinuses ensures more complete cleansing and humidification of the inhaled air, and also explains the rarity of diseases such as sinusitis. In some cases, children may still develop chronic sinusitis, and within a short period of time.

Nasolacrimal duct

The nasolacrimal duct is quite short and located very close to the eye.

Because of this structure, conjunctivitis quickly appears during inflammation and the development of pulmonary diseases.

The child's pharynx is also short, narrow and small. In the pharynx there is a lymphoid ring in which the tonsils are located. The child has 6 of them. When examined by a doctor, the pharynx is often visible. This is the name given to the accumulation of various tonsils at the base of the pharynx.

The structure of the tonsils and the space around them is very loose, susceptible to infection. Because of this, infections easily enter the body, and the child often suffers from respiratory diseases. They are often located on the tonsils, adenoids and other elements of the respiratory system located in the pharynx. The pharynx connects to the auditory canals.

Because of this structure, infection can easily enter the child’s hearing organs. With age, the canals increase in size, and infections practically do not penetrate. Due to frequent diseases in the pharynx, the child may be subject to nervous system disorders, which may explain poor performance at school. Due to this type of breathing, it is possible to “acquire” an adenoid face: the child does not have nasal breathing, the mouth is constantly open, and there is a puffy face.

The epiglottis is also very small in a young child. Incorrect positioning can result in “heavy” breathing that is clearly audible to others. The epiglottis connects to the lower respiratory tract. When eating, it blocks the passage of food to the lungs. Performs a protective function.

Lower Paths

The lower respiratory tract consists of the larynx, trachea and bronchi, lungs and diaphragm. Their structure also differs. In general, the lower path system is more developed.

At birth, the baby's larynx is in a position that is much higher than usual. She is very mobile, and over time the position changes.

Its position is never the same; it is different for each child. The larynx has the shape of a funnel, tapers towards the subglottic space, the lumen of the larynx is narrow. In a newborn, the diameter of the larynx is only 4 mm.

The width of the larynx increases extremely slowly and only by the age of 14 does it have a diameter of 10 mm. Children's vocal cords are short. It is this fact, in addition to the high position of the larynx, that explains the high timbre of the voice. By the age of 10, the vocal cords lengthen and the timbre changes.

Thyroid cartilages

The thyroid cartilages have an obtuse angle. In boys, it becomes acute during adolescence, and the male larynx can already be seen. The mucous membrane is tender and loose. A large amount of lymphoid tissue in the larynx swells easily during an infectious disease, and heavy breathing occurs.

Trachea

The trachea in a child’s body is also located above the usual position of an adult. It is located at the level of the 3rd cervical vertebra; as the body grows, the trachea descends several vertebrae below. The trachea has a funnel-shaped structure consisting of 16 rings. With age, the rings fuse and a dense, cylindrical shape of the trachea is formed.

The trachea is relatively narrow. It has a large number of muscles, thanks to which the lumen of the trachea changes when breathing or coughing. The tracheal mucosa is tender and dry. Newborns under 2 years of age may experience snoring. This is due to the softness of the trachea. With the development of the whole organism and individual organs of the system, it becomes denser, and snoring syndrome disappears.

Bronchi

The trachea are fused with the bronchial tree. It consists of a right and a left part. The sizes of the bronchi are different. The right side is much wider and shorter, it is the main one. Most often, the right side is a continuation of the trachea. It is in this part that foreign objects that a child can inhale are detected.

The left side of the bronchi is narrow and long. The number of branches in the bronchi does not change with age, and the distribution of air during breathing remains constant. The bronchi have several layers of epithelium; ciliary function develops in the postuterine period.

The epithelium contains mucus, which has a cleansing function. Thanks to the large number of cilia, the mucus can move. Its speed is about 1 cm per minute. The cartilage in the bronchi is also very mobile and easily changes position. When they are irritated, asthma can develop.

Due to the poor development of elastic muscle tissue and the lack of coverage of the nerve fibers of the skull, the coughing force is not sufficiently developed. With age, the cough impulse becomes more powerful. This promotes bronchial activity and the development of ciliated epithelial function.

With a respiratory disease, the amount of mucus in the bronchi also increases. With a slight increase, the lumen of the bronchi is reduced several times.

This leads to difficulty breathing. Coughing does not help get rid of the infection in the bronchi, and the lung tissue succumbs to disease. The tissue easily swells and clogs the gaps.

Lungs

The lungs in a child's body have a similar structure to the lungs of an adult. They are also divided into segments: in the right lung there are 10 segments, in the left - only 9. There are 3 lobes in the child’s right lung (while in the left lung there are only 2).

The segments are easily separated from each other by grooves and connective tissue. A peculiarity of the structure of the lungs of a child’s body is the end of the lungs in the form of a sac of alveoli. They resemble the lacy edges of a knitted napkin. With age, the sacs form new alveoli; the acinus has clusters of alveoli of a standard shape.

A baby born at term has about 24 million alveoli. For 3 months of life, they become several times more. But even this number of alveoli in newborns is 3 times reduced. The inner surface is lined with a surfactant substance.

It is this that allows the alveoli not to stick together and always have a round shape. It also performs a protective function against various microbes, viruses. The substance is formed in the last months of intrauterine development. Surfactant deficiency can cause respiratory syndrome.

The baby's alveoli increase in size. In addition, the number of alveoli in the lungs is also increasing. In the first year of life, the diameter is 0.05 mm, and by the age of 5 it increases almost 3 times. The tissue between the alveoli contains many vessels, fiber and little connective tissue.

Therefore, the lungs of young children are less airy. With age, this “defect” disappears. The density of the alveoli allows respiratory inflammation to occur for no apparent reason.

The pleura in young children is thick and loose, has many folds, villi, outgrowths. It is in these places that pockets of pulmonary infections are created.

Mediastinum

It is quite large in size compared to an older organism. Its main part is the root of the lung. The organ consists of large bronchi, vessels and lymph nodes. Due to the large size of the lymph nodes, children are more likely to get sick (but the lymphatic system is not underdeveloped or bad).

A child's diaphragm is an important part of breathing. It provides depth of inspiration. With its poor development, the baby can observe shallow breathing, which can also be caused by stomach cramps, gases in the intestines and other gastrointestinal disorders. To determine the correct development of the diaphragm, you can use palpation of the chest.

Features of the functioning of the respiratory system in children

The body's respiration is necessary to supply the organs with oxygen. It is conventionally divided into external and internal. External respiration begins with the entry of air into the upper tracts and ends with gas exchange in the alveoli. The effectiveness of external respiration is determined by 3 factors:

• ventilation of the alveoli;
• intensity of capillary activity;
• diffusion of gases.

Ventilation of the alveoli depends not only on the work of the lungs, but also on nerve signals supplied from the central nervous system. Violation leads to an increase in the load on the respiratory organs and their efficiency. Diffusion and intensity of capillary activity depends on the pressure difference during gas exchange and particle concentration.

Internal respiration depends on the metabolism occurring in the organs and cells of the child’s body.

The functioning of the respiratory system in young children is accompanied by the following features:

• shallow breathing;
• shortness of breath;
• arrhythmia;
• respiratory failure.

The uniqueness of the baby’s respiratory system completely suits the body’s oxygen needs. From the first days of life, the system quickly develops and adapts to the new environment.

The first need for oxygen in a newborn is caused by a sharp decrease in the level of oxygen in the body at the moment the umbilical cord is clamped. It is through this organ that the fetus in the womb receives oxygen. In addition, the body finds itself in a different environment: dry and cold.

Signals about a lack of oxygen enter the central nervous system and are then transmitted to the respiratory organs. At the time of birth, the airways are cleared of liquids: some of the liquid is absorbed into the baby’s tissues and lymph.

In the first year, children often experience respiratory arrhythmia. Over time, it should pass, and breathing will return to its usual rhythm.

Shallow breathing is caused by poor development of the diaphragm and structural features of the chest. The breathing rate of a newborn is 40-60 breaths per minute. With age, the breathing rate decreases to 20 breaths per minute. This norm corresponds to 10 years of age.

The number of breaths in an adult should not exceed 21 breaths in one minute. The high frequency of inspiration is associated with its depth. The baby cannot take a deep breath from the small volume of the lungs and undeveloped muscles.

From the first years of life, the baby’s percussion tone should be clear with a slight tint. Normal breath sounds are different for every age. In infancy, breathing seems to be weakened. In fact, these are the features of the baby's shallow breathing. From the age of two, breathing is heard more clearly. School-age children and older have breathing like adults.

A child's lung capacity is much lower than that of an adult. Therefore, the absolute value of the breathing volume is much lower. But in terms of body weight, this figure is much higher. With age, indicators change. Gas exchange in children is much more intense due to the presence of a large amount of vascularization of the lungs. This process allows you to quickly deliver oxygen to the organs and tissues of the body and remove carbon dioxide.

The following methods and signs will help to distinguish the functional features of a child’s breathing.

Survey

A survey of the child or mother during a visit to the doctor will reveal possible complications and features of the development of the respiratory system. Here you need to pay attention to the presence of nasal discharge, breathing, and cough. During an external examination, various methods are used to identify pathologies and complications.

Cyanosis and shortness of breath

Cyanosis is expressed by the blueness of certain areas of the child's skin. These could be nasolabial folds, fingers or toes. It can appear during certain manipulations or be permanent.

Shortness of breath occurs due to the participation of the child’s muscles during breathing or in the presence of bronchopulmonary diseases.

Cough

The presence of a disease can be determined by the child's voice. A hoarse and hoarse voice is a clear witness to an infectious disease. A nasal voice indicates a runny nose. A rare and periodic bright cry of a baby may indicate periodic abdominal pain or otitis media. A monotonous cry may indicate damage to the nervous system.

Using a cough, you can assess the baby’s health status. Even if there is no cough, it can be induced artificially and the condition of the small patient can be determined. For example, a dry or wet cough indicates the presence of a respiratory disease. A cough that ends in vomiting can occur with whooping cough.

If you suspect any disease, it is best to undergo an examination using modern medical equipment. This will allow you to accurately determine the nature of the disease or refute it.

Finally

The respiratory system of a child at an early age is poorly developed. Many organs are still poorly developed, small in size or not fully formed. This contributes to frequent illnesses. The structure of the respiratory system is very similar to that of an adult.

The structural features of the respiratory organs of the upper tracts make it possible to better moisten and purify the air entering the child's body. Due to the absence of some sinuses, infections easily penetrate the baby's body and spread there. The lower respiratory tract is better formed and has a structure that is similar to that of an adult organism.

The functioning of the respiratory organs is due to the frequency of inhalations and exhalations, the lack of rhythmic breathing, structural features and development of the respiratory organs, gas exchange, metabolism and other factors. Knowing the distinguishing features will help parents worry less about their baby, identify possible diseases at an early stage.

Age-related changes in the respiratory system: structural and functional development.

Airways and alveoli

Lung formation occurs between 4 and 8 weeks of pregnancy. At this time, the rudiments of the lungs divide into the main bronchi, at the 6th week all subsegmental bronchi are already present, and by the 16th week the structure of the bronchial tree is similar to that in adults. When airway development is complete, the terminal bronchi are remodeled and divide to form large sacs, or alveolar precursors, that can support gas exchange. True alveoli form immediately before and after birth; During postnatal growth, the alveoli are thin and septate.

Newborn babies have about 24 million alveoli; by the age of 8, their number increases to 300 million. After that, further growth of the lungs is primarily the result of an increase in the size of the alveoli.

The tissues of the lungs of newborns are less elastic than in adults, elastin is present only on the alveolar canal. By the age of 18, elastin spreads to the alveoli and its content becomes maximum. It then slowly decreases over the next 50 years. Lung compliance is inextricably linked with the amount of elastin, so the peak of compliance is observed at puberty. It is reduced in young children and very old people. Fluctuations in tidal volumes occur until approximately 5 years of age.

Blood supply to the lungs

At 14 weeks of gestation, the main arteries in the lungs are already present. By week 20, the branching pattern is similar to that of adults, and there are also additional collateral vessels. During intrauterine life, accessory arteries develop simultaneously with the airways and sacs. Bronchial arteries appear between the 9th and 12th weeks of pregnancy. The arterial wall develops as a thin elastic plate at 12 weeks' gestation, and muscle cells are present as early as 14 weeks' gestation. By week 19, the elastic tissue reaches the seventh order of arterial branching, and the muscle tissue extends distally. In the fetus, the muscular layer of the arteries ends at a more proximal level than in children and adults. The muscular layer of arteries is thicker than that of similarly sized arteries in adults. The pulmonary arteries are severely narrowed until the second half of pregnancy. In the lamb fetus, pulmonary blood flow accounts for only 3.5% of total ventricular volume during the second trimester and is only 7% before birth. Immediately after birth, pulmonary blood flow increases to nearly adult levels. The development of the pulmonary venous system is a mirror image of the development of the arterial system.

The pulmonary arteries continue to develop after birth, arterial formation accompanies the branching of the respiratory tract until 19 months of age, and collateral arteries continue to develop until 8 years of age. As the alveolar size increases, the pattern of acini branching becomes more extensive and complex. The arterial structure also undergoes changes such as an increase in the size of the existing arteries, the thickness of the muscular layer of the arteries decreases to adult levels during the first year of life.

Biochemical development

At 24 weeks of gestation, the cuboidal alveolar epithelium increases in volume and type I pneumocytes become the lining and supporting cells of the alveoli. At this time, large type II cells also develop, producing and storing surfactant. In humans, surfactant appears at 23-24 weeks of gestation, and its concentration increases during the last 10 weeks of intrauterine life. Surfactant is released into the alveoli at approximately 36 weeks of gestation, allowing normal extrauterine life.

Breathing transition: from placental to pulmonary

At approximately 24 weeks of gestation, the lungs are capable of gas exchange outside the uterus. However, a number of important circulatory and mechanical changes must occur immediately after birth to ensure adequate gas exchange in the lungs.

Ventilation begins to match perfusion in the first hours of life. Initially, intrapulmonary shunting appears from right to left through the atelectatic areas of the lung, as well as shunting from left to right through the ductus arteriosus and, slightly, from right to left through the oval window. RaO 2 within 50-70 mm Hg. Art., which is three times the adult norm, indicates a shunt from right to left.

The transition from fetal to neonatal respiration and circulation is dynamic. Postnatally, the pulmonary vasculature remains constricted when exposed to acidosis, cold, or hypoxia. When the pulmonary artery is narrowed, shunting of deoxygenated blood from right to left through the patent foramen ovale and ductus arteriosus increases, and consequently pulmonary blood flow decreases. The presence of such active pulmonary vasoconstriction is called persistent pulmonary hypertension of the newborn or persistent fetal circulation. It also occurs in patients with congenital diaphragmatic hernia, meconium aspiration, and sepsis.

Biomechanics of children's breathing

To ventilate the lungs, the respiratory muscles must overcome static-elastic and dynamic resistance forces. Changes in these opposing forces during postnatal development affect lung capacity, breathing patterns and work.

Lung compliance depending on age

Lung compliance changes with age due to changes in the alveolar structure, the amount of elastin and surfactant. At birth, compliance is low because alveolar precursors have thick walls and a reduced amount of elastin. Surfactant deficiency (eg, in hyaline membrane disease) further reduces lung compliance. As a result of further development of the alveoli and elastin, lung compliance improves during the first years of life.

Chest wall

Babies have a very pliable chest wall because their ribs are made of cartilage. Because of the box-like configuration of the infant's chest, its elastic thrust is less than that of the dorsoventrally flattened adult chest. Adults have a significant proportion of slow-twitch, fatigue-resistant fibers characterized by high levels of aerobic metabolism in both the diaphragm and intercostal muscles. While adults have 65% of these fibers in the intercostal muscles and 60% in the diaphragm, newborns have only 19% to 46% of these fibers in the intercostal muscles and 10% to 25% in the diaphragm. Consequently, children are more prone to muscle fatigue and decreased chest wall stability. The result of a distensible chest wall and poorly distensible lungs is alveolar collapse and decreased tidal volume at rest (functional residual capacity). Despite this tendency to collapse the lung, the child maintains a large dynamic functional residual capacity through rapid breathing, laryngeal opening, and chest wall stabilization with increased intercostal muscle tone during expiration.

Upper respiratory tract

There are several anatomical differences between the upper airway in children and adults that affect the ability to maintain patency. The more anterior and cephalad position of the larynx in children makes the “sniffing position” ideal for mask ventilation and tracheal intubation. Excessive neck extension can actually lead to airway obstruction. The narrow part of the adult respiratory tract is the area of ​​the vocal cords. Before the age of 5 years, the narrowest part of the child's airway is the cricoid cartilage region, since the larynx is located more cranial in the back than in the front, causing the cricoid cartilage to be shaped like an ellipse rather than a circle. By the age of 5, the back of the larynx descends to adult level. An endotracheal tube that passes easily through a small child's vocal cords can cause ischemic injury to the distal larynx. The cricoid constriction and highly pliable tracheal cartilage provide an adequate seal around the uncuffed endotracheal tube. Children under 5 years of age do not usually require a cuffed endotracheal tube, but some practitioners routinely use such tubes in this age group of patients.

Expiratory airway closure

The elastic properties of the lungs closely correlate with expiratory airway closure. Expiratory airway closure (or lung closure volume) is the volume of the lungs at which the terminal airways close and gas becomes trapped (behind the closed airway). Large lung closure increases dead space ventilation, leading to atelectasis and right-to-left shunting. Elastic tissues help keep the airways open, so the more elastic stroma in the small airways, the less lung volume there is to close the small, cartilaginous airways. Lung closure volume is small in late adolescence and relatively large in the elderly and children. Children overcome complications caused by large volume of lung closure and secondary atelectasis by increasing breathing, constant activity, and crying. Expiratory airway closure becomes a serious problem in inactive, sedated and anesthetized infants.

Resistance forces

In newborns, the airways are small with high resistance or low conductivity. The diameter of the small airways does not increase significantly until about 5 years of age, which means that young children have increased airway resistance at rest and are especially vulnerable to diseases that cause further narrowing of the airways (smooth muscle spasm, airway swelling/inflammation). Normal high airway resistance in neonates and young children helps maintain functional residual capacity.

Breathing regulation

Newborns have a unique regulation of breathing. Initially, hypoxia increases ventilation for a short time. This increase is followed by a steady decrease in ventilation. In premature babies the response is more pronounced. In full-term newborns, it disappears after a few weeks. Periodic breathing is also common in infants, especially premature infants, which is likely due to insufficient development of the brain's respiratory centers.

Oxygen transport: addition and release of oxygen

Fetal hemoglobin contains lower levels of 2,3-DPG, and the oxygen half-saturation pressure of hemoglobin ranges from 18 mmHg. Art., which is significantly lower than in adults (27 mm Hg. Art.). This low half-saturation pressure in the fetus allows for good oxygenation of hemoglobin at low placental oxygen tension, but complicates the release of oxygen in the tissues. From 3 to 6 months after birth, fetal hemoglobin is replaced by adult hemoglobin. The increased concentration of fetal hemoglobin and its increased oxygen content are beneficial to the fetus because it allows the 20 ml of oxygen contained in 100 ml of blood to be delivered to the brain and heart. This oxygen content is similar to that of adults breathing room air. The oxygen requirement of newborns at birth ranges from 6 to 8 ml/kg/min. It decreases to 5-6 ml/kg/min in the first year of life. A reduced ventilation-perfusion ratio, decreased oxygen pressure in fetal hemoglobin, and signs of progressive neonatal anemia may cause difficulty in delivering sufficient oxygen in the first months of life. Infants compensate with cardiac output of approximately 250 ml/kg/min during the first 4–5 months of life.

Respiratory failure of a child

Respiratory failure is the inability of the lungs to adequately oxygenate the blood and remove carbon dioxide from the arterial blood of the lungs. There are many causes of respiratory failure, including low ambient oxygen concentrations, parenchymal and vascular diseases of the lungs.

A detailed history of the severity and frequency of respiratory disorders helps to make a differential diagnosis and choose the right treatment approach. There must be specific data including:

history of prematurity;

use of breathing equipment;

performing artificial lung ventilation;

extrapulmonary organ pathology;

family history of respiratory tract diseases.

Detailed feeding information and an updated growth chart can provide valuable information because growth failure can increase oxygen requirements. Typically, 1-2% of the total oxygen consumed is used for breathing. In case of respiratory pathology, up to 50% of total oxygen consumption can be used for breathing. Infants and children with respiratory failure often experience intercostal and suprasternal retractions (signs of increased respiratory work and oxygen consumption). Most infants and children have tachypnea, which also helps maintain functional residual capacity by reducing expiratory time. Breathing rapidly and shallowly requires less energy than taking deep breaths. Infants with respiratory failure often have cyanosis of the lips, skin, and mucous membranes. However, it is often difficult to recognize changes in skin color if the PO 2 is not lower than 70 mmHg. Art. The symmetry of the chest in the act of breathing should be noted. Uneven participation of the chest in breathing may indicate pneumothorax or bronchial obstruction. The small chest volume facilitates easy transmission of breathing sounds from one side to the other. Breath sounds may remain normal, even with pneumothorax. In infants and young children, bloating can make breathing significantly more difficult.

Radiological examination of the nasopharynx, neck and chest can provide meaningful information regarding the cause and severity of respiratory dysfunction. Fluoroscopy may be used to evaluate the airway and diaphragmatic movement in an unattached child. However, for such examinations, the child must be accompanied by someone who is able to provide mechanical ventilation if he is able to leave the intensive care unit.

Pulmonary function testing helps evaluate respiratory function, but because of the lack of interaction, these tests are difficult to perform in children younger than 5 years without sedation, which can be dangerous in a nonintubated child with respiratory failure. Most pulmonary function tests require the use of a form-fitting mask, which in itself can be problematic. With the trachea intubated, lung volumes, expiratory flow rates, inspiratory compliance, and inspiratory force can be easily measured; in fact, most mechanical ventilators are now equipped with monitors that allow these parameters to be measured regularly.

Arterial blood gas analysis is used to determine the efficiency of gas exchange. Measurements of PaO 2 make it possible to determine the alveolar-arterial oxygen gradient and shunting of blood through the lungs from right to left.

Another indicator of lung function is the elimination of CO 2 from arterial blood. Impaired removal of CO 2 from the pulmonary arterial blood indicates an uneven distribution of blood flow in the lungs and, in particular, speaks of increased dead space.

Umbilical artery catheterization is common in neonates, so those working with these infants can obtain arterial blood and continuously measure arterial blood pressure. These catheters are relatively easy to install and maintain. The catheter tip should ideally be positioned at or slightly above the level of the aortic bifurcation and below the level of the renal arteries. When the child's condition is stabilized, a peripheral catheter must be installed and the catheter removed from the umbilical artery. All intra-arterial catheters have the potential to cause thromboembolic disease. Caution must be exercised when using arterial catheters to prevent cerebral or cardiac embolism. With proper installation and maintenance, serious arterial complications are rare. Although arteries that are catheterized for a long period may become occluded, they have the ability to recanalize within a short period of time.

Minimally invasive methods for monitoring gas exchange have been developed. Transcutaneous electrodes accurately measure oxygen and carbon dioxide levels in infants and young children, but lose accuracy when hypoperfused. The electrodes take some time to warm up, making spot checks difficult. These monitors are best used in older children and adults. Pulse oximeters are commonly used in the care of seriously ill infants and children because they are accurate, require little warm-up time, and require little skill to use. The sensor easily covers the entire hand or foot of a small child. End-tidal CO2 monitoring allows continuous measurement of carbon dioxide elimination. However, this technology has limited use in young children due to the increased dead space and heavy weight of the endotracheal tube sampling device, which can kink the endotracheal tube and lead to accidental extubation.

Causes of respiratory failure

The causes of respiratory failure depend to some extent on the age of the patient. Respiratory failure in newborns is often the result of congenital abnormalities and immaturity of the lungs and pulmonary blood vessels.

Congenital abnormalities may include:

respiratory tract malformations;

dysgenesis;

dysfunction of the lungs or other organs;

pulmonary vascular abnormalities.

Manifestations of immaturity may include:

apnea of ​​prematurity;

hyaline membrane disease;

abnormal synthesis;

secretion of surfactant.

During the perinatal period, newborns are susceptible to infections and stress. Persistent pulmonary hypertension can complicate neonatal pulmonary and extrapulmonary pathology. Regardless of the cause, respiratory failure can be classified as hypoventilation syndrome in patients with normal lungs, with internal alveolar and interintestinal pathology, and with obstructive airway diseases.

Hypoventilation syndromes in children with normal lungs

The causes of hypoventilation are neuromuscular diseases, central hypoventilation, and structural/anatomical disorders of lung expansion (upper airway obstruction, massive bloating). These conditions are characterized by insufficient expansion of the lungs, the presence of secondary atelectasis, intrapulmonary shunting from right to left and systemic hypoxia. Atelectasis and secondary contraction of FRC increases the work of the respiratory muscles. This consists of increasing the NPV with a reduced DO. The breathing pattern ultimately increases the incidence of atelectasis and shunting. As a result, children with essentially normal lungs and hypoventilation syndrome have tachypnea, reduced tidal volume, increased respiratory muscle function, and cyanosis. Chest radiographs reveal small lung volumes and miliary or lobar atelectasis. Pathological processes are quickly eliminated using positive pressure ventilation and positive end-expiratory pressure (PEEP).

Primary pulmonary alveolar or interstitial pathology

Internal lung diseases involving the alveoli or pulmonary interstitium reduce the elasticity of the lungs and reduce the lumen of the airways, which leads to atelectasis and increased work of breathing. The elasticity of the lungs is reduced due to edema or inflammation of the alveoli, or fibrosis of the interstitium. The "harder" the lungs, the greater the negative intrapleural pressure required for the passage of air, thereby increasing the work of breathing and the risk of pneumothorax.

Obstructive airway disease

Airway obstruction can be external or internal. Intrinsic small airway obstruction commonly occurs in bronchiolitis, bronchopneumonia, asthma, and bronchopulmonary dysplasia (BPD). Airway obstruction reduces airway patency, increases airway resistance and increases work of breathing. Partial obstruction prevents exhalation more than inhalation and results in a gas trap or focal emphysema. Complete obstruction of the airways leads to atelectasis and shunting of blood from right to left in the lungs. Patients with small airway disease typically have a combination of complete and partial obstruction, patchy collapse, and hyperinflation of the lung. Collapsed areas cause intrapulmonary shunting of blood from right to left, and overinflated areas increase the amount of dead space. If the lung is overinflated, its compliance decreases and the work of breathing increases. The clinical and radiological picture varies due to varying degrees of collapse and hyperextension of the lung.

Thus, all causes of respiratory failure have a similar pathophysiology: atelectasis and decreased functional residual capacity, with intrapulmonary shunting of blood from right to left, or overdistension of the alveoli, with increased dead space and decreased CO 2 elimination (or both). The increased work of breathing associated with all forms of respiratory pathology can lead to fatigue and a breathing pattern that further complicates the initial process. If increased work of breathing is not detected promptly and treated, it can lead to apnea, hypoxia and cardiac arrest in young children.

Treatment of respiratory failure

Treatment for respiratory failure includes:

ensuring airway patency;

increase in oxygen concentration during inspiration;

elimination of airway obstruction;

treatment of infections;

correction of fluid overload;

correction of all extrapulmonary anomalies;

purpose of artificial ventilation.

The use of exogenous surfactant, high-frequency ventilation, mechanical ventilation with lung protection, inhaled NO, inclined positioning, humidified ventilation, and extracorporeal membrane oxygenation (ECMO) may be effective in some cases.

Infants and young children often need help maintaining an open airway. To prevent the occurrence of aspiration or gastroesophageal reflux and to minimize the effects of abdominal bloating, specific manipulations, such as creating a semi-upright position, are necessary. In general, it is appropriate to keep the head in the midline and minimize excessive head flexion.

The inhaled oxygen concentration can be increased by using a form-fitting mask. Nasal cannulas are often helpful, but may cause agitation in some children and may negate the benefit of high FiO values. Directional oxygen flow, face masks, and oxygen tents are less aggressive and generally better tolerated by children.

Upper airway obstruction can be relieved by placement of a laryngeal mask, endotracheal tube, oropharyngeal or nasopharyngeal airway, or tracheostomy. Often, inhaled racemic epinephrine and intravenous steroids reduce subglottic edema, antibiotics reduce infectious edema, and beta-receptor agonists and inhaled anticholinergics relax bronchial smooth muscle. Patients with pneumonia should be tested for bacterial, viral, or fungal pathogens and treated with appropriate antibiotics. Pulmonary edema is treated with fluid restriction and administration of diuretics and cardiotonic or vasoactive drugs. Good enteral or parenteral nutrition, fluid and electrolyte balance, and adequate cardiovascular and renal function are all part of respiratory support. Mechanical ventilation is the main treatment for respiratory failure. Here are some extrapulmonary indications for mechanical ventilation:

Resuscitation for vascular insufficiency.

In situations where the cardiovascular system is unstable, mechanical ventilation is the safest method. In cardiac arrest, respiratory support is mandatory, although mask ventilation with an AMBU bag may be effective initially. Patients rarely die from missing an endotracheal tube. The death of the patient is usually due to a lack of oxygen, which is sometimes, in a hurry, forgotten to connect to the endotracheal tube. Artificial lung ventilation is used after cardiac surgery (to ensure adequate gas exchange) until blood circulation stabilizes. Mechanical ventilation also reduces the risk of unwanted cardiovascular decompensation.

Respiratory support.

Intentional hyperoxia is sometimes used to increase vascularity in some newborns to expand the lungs to initiate other treatments. Mechanical ventilation is also used to reduce intracranial pressure (ICP), which occurs due to the occurrence of a small respiratory alkalosis and a decrease in cerebral blood volume. Thereafter, mean arterial pressure should be maintained at or above the pre-hyperventilation level to prevent further cerebral ischemia. Mechanical ventilation may also be required in children with conditions that predispose to respiratory failure (morbid obesity, sepsis, malnutrition, and kyphoscoliosis).

Reduced work of breathing.

Reducing respiratory oxygen capacity in mechanically ventilated patients may improve the ability of some to experience basic physiological responses. Children with BPD may require long-term mechanical ventilation to conserve the energy expended in breathing and to use that energy for growth.

Ventilation therapy

Respiratory support is provided through continuous positive airway pressure, intermittent positive pressure ventilation, and negative pressure ventilation. Positive pressure ventilation is typically administered through an endotracheal tube or tracheostomy. Ventilation in some infants and children can be maintained with continuous positive airway pressure via a mask, noninvasive ventilation, or high-flow nasal prongs. Orotracheal intubations are easier to perform than nasotracheal intubations, especially in emergency situations. The appropriate size of endotracheal tube should be carefully selected. There is a formula that can be used to calculate the required tube size for children over 2 years old: (age+16).

This formula determines the internal diameter of an appropriately sized endotracheal tube. If the correct size is used, there should be some air leakage when positive pressure (20 to 30 cmH2O) is applied. When a disproportionately large endotracheal tube (ETT) is used, especially in children with inflammatory diseases of the upper respiratory tract such as laryngotracheobronchitis, serious damage to the larynx and subglottic region can occur. Because of the more flexible tracheal cartilage and the relatively narrow subglottic space in children younger than 5 years, an uncuffed ETT generally provides an adequate seal. However, if the patient has a lung disease that requires high pressure ventilation, it may be appropriate to use cuffed tubes. A small diameter cuffed ETT is often used in the small pediatric intensive care unit, but in such cases care should be taken to ensure a small air leak of 25 to 30 cmH2O. Art. Typically, a cuffed tube will seal air leaks around the ETT, and overinflating the cuff can stop venous flow and injure the airway. There are currently no data on the long-term safety of cuffed ETT use in young children.

When performing tracheal intubation, it is important to correctly position the endotracheal tube. If it is installed correctly, then the movements of the chest are symmetrical and respiratory sounds are heard equally on both sides, when listening in the armpits. An electronic or colorimetric CO 2 detection system helps confirm that the ETT is actually in the trachea and not the esophagus. If the double lines on the ETT are at the level of the vocal cords, this usually indicates the correct position of the ETT. Another way to properly position the tube is to advance it into the right main bronchus and then listen for breath sounds in the left axilla (breath sounds will decrease). The ETT must be withdrawn slowly. When sounds are heard on the left side when breathing, you need to further tighten the tube by 1-2 cm, depending on the size of the child. If the breath sounds are the same, the tube should be secured in place. On a chest radiograph, the tip of the ETT should be positioned halfway between the vocal cords and the carina. In young children the distance between the carina and the vocal cords is very short. Therefore, it is possible to inadvertently place an ETT in the main bronchus. The ETT moves in the airway when the head is flexed. Extension moves it towards the vocal cords. Turning the head to the side can cause obstruction of the ETT tip if it comes into contact with the tracheal wall, which can lead to hypercapnia and/or hypoxemia.

Typically, an endotracheal tube is used for more than 2 weeks before tracheostomy. This is possible with the use of an appropriate respiratory gas humidifier, improved endotracheal suction, monitoring (SaO 2) and excellent care.

Every caregiver must be constantly prepared for the possibility that the EET may become obstructed by secretions, or that extubation or intubation of the main bronchus may occur accidentally. In newborns, endotracheal tubes with a Murphy's eye are usually more often obstructed by secretions than without it. Murphy's eye is located very close to the end of the ETT. Once the ETT enters the main bronchus, the infant cannot breathe effectively through the peephole. Because the ETT is almost the same size as the trachea, it is virtually impossible for an infant to breathe around the tube. Thus, Murphy eye ETTs are dangerous and should probably not be used in young children. When children require the creation of an artificial airway for a long period of time for the purpose of mechanical ventilation, endotracheal sanitation, or to bypass the site of upper airway obstruction, a tracheostomy is performed. Accidental dislodgement of the tracheostomy tube and its release from the airway can be life-threatening. Removing the tracheostomy tube within the first 72 hours after insertion can be very difficult and create false passages that can prevent ventilation or cause pneumothorax.

Continuous positive airway pressure and positive end expiratory pressure (PEEP)

By creating continuous positive pressure (CPAP) in the airway, the child breathes on his own through a system that maintains a constant PEEP. With PEEP (or PEEP), the lungs are mechanically ventilated while maintaining constant end-expiratory pressure.

Continuous positive airway pressure is used with an endotracheal tube, nasal prongs, or mask. Since most newborns breathe through the nose, the use of continuous positive airway pressure through the nose is often effective, even in preterm infants. The success of its use depends on the size, condition of the child and whether the child was breathing through the mouth. Crying and mouth breathing may reduce the effectiveness of nasal continuous positive airway pressure because these actions reduce the pressure in the throat. When using continuous positive airway pressure through nasal prongs or a mask, bloating may occur. In this case, a gastric tube must be inserted for decompression. Use of a face mask in children and adults is effective for short periods. Prolonged use of a continuous positive airway pressure mask may result in necrosis of the face and/or eyes due to compression. Low to moderate PEEP levels can be maintained in children with an uncuffed ETT, but large gas leaks around the tube cause PEEP levels to become unstable. This problem can be solved by using a larger diameter tube or a cuffed ETT.

It is difficult to determine the optimal level of continuous positive airway pressure, or PEEP, but it is generally the lowest pressure level that maintains normal PaO 2 without excessively increasing PaCO. Too little pressure ineffectively increases PaO 2 , while too high a pressure overinflates the lungs and increases dead space ventilation. Low continuous positive airway pressure, or PEEP (2 to 5 cmH2O), is recommended for all children with an artificial airway.

The goal is to use the lowest level of continuous positive airway pressure, or PEEP, that adequately improves oxygenation with minimal impact on ventilation.

The first approach is to use a level of continuous positive airway pressure, or PEEP, that improves oxygenation and allows the FiO2 level to be reduced (to 0.6 or less).

The second approach is to increase end-expiratory pressure until the situation improves as much as possible.

Suter and coll. suggested that the best level for PEEP (or continuous positive airway pressure) is the level of end expiratory pressure that is necessary to maximize oxygen transport resulting from cardiac output and arterial oxygen content. This requires repeated cardiac output measurements and the use of a Swan-Ganz thermodilution catheter, which is rarely used in young children. Most clinicians approach the best levels of continuous positive airway pressure, or PEEP, by using levels that produce adequate PaO 2 and PaCO 2 and allow FiO to be reduced.

Positive pressure ventilation.

Mechanical positive pressure respirators are classified according to their regulation method as:

with a given volume;

with a given pressure;

with a given time.

In general, pre-setting devices by time or pressure is more convenient for use in infants and young children (<10 кг), тогда как респиратор с заданным объемом обычно используются у детей старшего возраста (>10 kg) and adults. Timed and pressure-controlled respirators have a number of benefits for infants and young children. Most of these patients are intubated with an uncuffed ETT, which results in varying degrees of gas leakage around the tube. This leakage, along with the relatively large compression of the breathing circuit volume compared to the tidal volume of infants, makes volumetric ventilation unreliable. The main problem with pressure or timed devices is that the volume delivered depends on the compliance of the child's chest and lungs and on airway resistance. High compliance of the lungs and chest wall can lead to excessive inflation of the alveoli and their rupture. However, decreased compliance can lead to hypoventilation and atelectasis.

Intermittent mandatory ventilation allows the child to breathe spontaneously from a low-resistance gas source while periodically receiving tidal volume using a mechanical respirator at preset intervals. Intermittent forced ventilation is produced using a continuous circuit or valve systems. Continuous chains are simple and do not require additional effort on the part of the patient during spontaneous breathing. Valve systems may not be effective in children who have a relatively high respiratory rate because the sensitivity and response time of the valve prevent the ventilator from working in sync with the patient's breaths. With high-pressure ventilation, each spontaneous breath is supplemented by the supply of gas at a given pressure. The patient determines the breathing rate and inhalation time, and the device determines the inspiratory pressure. Pressure maintenance ventilation increases tidal volume, can reduce the work of breathing and improve patient comfort. This mode of ventilation is usually used to wean the patient off mechanical ventilation. Pressure maintenance mode will not work if the patient has an abnormal respiratory pacemaker.

A better understanding of this pathology has led to ventilation modes that use fairly long inspirations, high positive end-expiratory pressure, and low tidal volumes. These lung-protective ventilation modes result in decreased minute ventilation and increased PaCO. They also reduce the shear forces acting on the terminal airways and return areas of the lung from dead space to the breathing process. Acid-base status may be relatively normal due to metabolic alkalosis caused by renal bicarbonate retention and administration of sodium bicarbonate or trisbuffer (trisaminomethane).

The optimal ventilation pattern for patients with obstructive airway disease is a higher rate and shorter duration of inspiration, and a longer expiration, to improve ventilation relative to the normal lung and remove gas from the obstructed part of the lung. Pharmacological bronchodilation is the mainstay of treatment for small airway disease. When performing mechanical ventilation in such patients, barotrauma and alveolar rupture usually occur.

Start of artificial ventilation.

The inhalation to exhalation ratio is 1-1.5:1 and the ventilation rate is relatively slow (<24 циклов/мин у младенцев и <16 циклов/ мин у детей) являются отправной точкой для многих пациентов. Параметры вентиляции изменяются на основании показателей газов крови, рН и сатурации.

Important criteria for determining the adequacy of ventilation are chest expansion, lung auscultation and adequacy of alveolar ventilation (determined by PaCO 2). Peak airway pressures should be measured as frequently as possible and as close to the ETT as possible.

You should start using PEEP from a level of 3-4 cm of water. Art. and increase it gradually by 2 cm until SaO is adequate. Some children need an end-expiratory pressure of more than 20 cmH2O. Art.

Initiation of positive pressure ventilation can lead to systemic hypotension, which is usually treated with an infusion of 10-20 ml/kg of crystalloids, colloids or blood products. It is necessary to measure CVP at a PEEP value of more than 10 cm of water. Art. Measurement of intravascular blood pressure and central venous pressure can detect the harmful effects of mechanical ventilation and positive airway pressure on the cardiovascular system.

Auxiliary pharmacological therapy: analgesics and sedatives. Sedation is often required to help keep children conscious and in sync with mechanical ventilation. The amount of sedation needed depends on the child's age, size, underlying medical condition, and the amount of ventilatory support needed. Some babies are calm enough to not require sedation. Sedation allows patients to breathe in sync with the respirator, which reduces peak airway pressure and eliminates coughing and straining, which can cause gas to leak from the lungs. Continuous infusion of fentanyl (1-2 mcg/kg/h) provides analgesic and sedative effects. However, this may result in the need to increase the volume of fentanyl administered on subsequent days to maintain the same level of sedation. Other drugs such as lorazepam (0.1–0.2 mg/kg IV every 4–6 hours) or midazolam (0.05–0.2 mg/kg/hour) may be a useful adjunct to opioids. Typically, these drugs have minimal cardiovascular effect when the vascular volume is sufficient. However, administration of lorazepam to preterm neonates for several days may result in steroid-sensitive hypotension due to drug accumulation in the body. In premature newborns, the half-life of lorazepam is about 72 hours. Administration of the drug every 4-6 hours leads to its accumulation in the blood and tissues.

Muscle relaxants increase the compliance of the chest wall, reduce oxygen consumption and facilitate artificial ventilation. When using them, therapy must be supplemented with drugs that cause amnesia, sedation and analgesia.

Pancuronium and vecuronium are the most commonly used muscle relaxants in the PICU. The standard dose of pancuronium is 0.1 mg/kg intravenously every 1-1.5 hours or 40-100 mcg/kg/hour as an infusion. Pancuronium-associated tachycardia is an unwanted side effect in adults but is generally desirable in infants and children because it helps maintain normal cardiac output. Vecuronium (0.08-0.2 mg/kg, followed by infusion of 60-150 mcg/kg/h) causes less tachycardia than pancuronium; The use of cisatracurium (0.1-0.2 mg/kg, followed by an infusion of 60-120 mcg/kg/h) is often appropriate because its elimination does not depend on the functional state of the kidneys or liver. If these drugs are prescribed for more than one day, a way to avoid their accumulation in the plasma and long-term paralysis should be considered by taking regular “days off” from them.

Cancellation of mechanical ventilation.

Criteria for ventilator withdrawal are poorly defined. In general, weaning of ventilatory support begins when the child is cardiovascularly stable and alert and alert. Mechanical ventilation should not be withdrawn if there is a significant risk of acute cardiac decompensation. It is best to correct severe anemia, hypoglycemia or hyperglycemia, hypernatremia, hypochloremia, or malnutrition before discontinuation, as these metabolic disorders in the child impair the child's ability to wean from mechanical ventilation. Before discontinuation is considered, the child must be able to produce an airway pressure (inspiratory force) of at least -20 cmH2O. Art. and inhale at least 10 ml/kg of gas at maximum effort (vital capacity).

Shunting of blood through unventilated areas of the lungs, leading to hypoxemia and tissue hypoxia, should be reduced by improving lung compliance, because otherwise pneumothorax and/or pneumomediastinum may occur.

The operating mode of the ventilator is usually not reduced until arterial blood gas levels stabilize, the inhaled oxygen concentration is less than 0.6, and PEEP is less than 10 cmH2O. Art. and peak airway pressure below 30-35 cm of water. Art.

There should be no residual effects from the muscle relaxants, and the level of sedation should be minimal. Neuromuscular blockade can be eliminated by intravenous administration of neostigmine (0.050.07 mg/kg) and glycopyrrolate (0.01 mg/kg); acceptable neuromuscular function should be confirmed using a peripheral nerve stimulator. When all these indicators are in order, the respirator operating mode is gradually reduced over several hours or days.

Withdrawal should continue until arterial blood gases remain within acceptable limits and until the child's clinical condition has stabilized. When voluntary ventilation is increased, the increased work of breathing can worsen the child's condition. Danger signs include tachycardia, hypertension or hypotension, tachypnea, increased work of breathing, and anxiety. If these symptoms occur, discontinuation should be discontinued and respiratory support should be increased. Frequent assessment of arterial blood gases and the child's clinical condition is necessary throughout withdrawal. If the child has residual lung disease and decreased lung compliance, further decreases in functional residual capacity and increased hypoxemia may delay discontinuation. The risk of these potential problems can be minimized by using moderate levels of continuous positive airway pressure, or PEEP (5 to 10 cmH2O) during withdrawal. The functional residual capacity is similar to that of neonates on mechanical ventilation with a PEEP of 2 cmH2O. Art., as after extubation of the trachea.

Tracheal extubation should be performed by a specialist as reintubation may be required. After tracheal extubation, FiO2 usually increases by 20%. Adult patients are advised to breathe deeply, cough, and clear secretions from the respiratory tract as often as possible. Forced spirometry, early mobilization, and chest physical therapy are important components in recovery from respiratory failure.

Before extubation, it is necessary to assess the quality and volume of tracheal secretions; it will be difficult for the patient to cleanse large volumes of thick secretions after extubation. In general, tracheal extubation is best performed when full medical staff are available to closely monitor the child and a chest x-ray is performed. If withdrawal of mechanical ventilation and tracheal extubation have been carefully thought out and performed, then reintubation is relatively rare.

High frequency ventilation.

High-frequency ventilation provides a smaller tidal volume than anatomical dead space at high respiratory rates (150 to 3000 breaths/min). Several different types of ventilators are effective, such as high-frequency jet respirators, high-frequency oscillating respirators, and flow interrupters. Each differs in technical design and clinical application; they can be differentiated by the mechanism of gas exchange.

A high-frequency oscillating respirator is commonly used for neonates and children with severe lung disease and respiratory failure. Its use has reduced the number of infants requiring extracorporeal membrane oxygenation (ECMO). High-frequency oscillating ventilation has also been successfully used in the treatment of children with acute homogeneous interstitial and alveolar diseases. Due to the physical limitations of the equipment, this form of ventilation is less effective in treating older children and adults. Jet ventilation is used to treat respiratory failure from many causes, although the main indication for its use is the treatment of barotrauma or bronchopleural fistula.

Exogenous surfactant

Exogenous surfactant therapy has now become the standard treatment for intrinsic surfactant deficiency in premature infants, with increased survival rates while reducing the need for mechanical ventilation and ECMO. The use of exogenous surfactant in older children and adults is not effective because the causes of the disease are different. Elderly patients are more likely to have problems with surfactant function rather than surfactant quantity.

Extracorporeal membrane oxygenation (ECMO)

ECMO is the standard of care for children older than 34 weeks of age with acute respiratory failure that does not respond to standard therapy. More than 24,000 infants, with a predicted mortality rate of 80% to 85% with usual management, have been treated with ECMO, and more than 80% of these patients survive. About 30% of children with heart disease (especially myocardium) are saved thanks to ECMO. Most ECMO were veno-arterial, where blood is taken from the venous system and returned to the ascending aorta. Venoarterial ECMO supports respiratory and cardiac functions. Venovenous ECMO is less effective, but it preserves pulmonary blood flow and avoids catheterization of large arteries. Venovenous ECMO is less effective in patients with myocardial dysfunction. However, it is rapidly gaining popularity and is used as much or more often than veno-arterial ECMO. The population of neonates eligible for ECMO is also changing. Exogenous surfactant, inhaled NO, and the use of a high-frequency oscillating respirator have significantly reduced the need for extracorporeal membrane oxygenation and shifted its use to a greater extent for patients with sepsis and multiple organ failure. Today's candidates for ECMO are patients who are more severely ill and generally have sepsis and multiple organ failure. ECMO for older children and adults with ARF continues to be investigated. Approximately 7000 pediatric ECMO patients have been enrolled worldwide. These were patients who were predicted to have a fatal outcome in 80%. About 50% of patients with ECMO survived. The reason for this difference in outcomes between the two age groups is due to the marked heterogeneity in age, diagnosis, management, and criteria for ECMO. In addition, there are few causes of ARF in newborns, and most of them are reversible. Older patients have more causes of ARF, which are not always reversible.

The formation of the tracheopulmonary system begins at the 3-4th week of embryonic development. Already by the 5th-6th week of embryo development, second-order branches appear and the formation of three lobes of the right lung and two lobes of the left lung is predetermined. During this period, the trunk of the pulmonary artery is formed, growing into the lungs along the primary bronchi.

In the embryo, at the 6-8th week of development, the main arterial and venous collectors of the lungs are formed. Within 3 months, the bronchial tree grows, segmental and subsegmental bronchi appear.

During the 11-12th week of development, areas of lung tissue are already present. They, together with the segmental bronchi, arteries and veins, form the embryonic segments of the lungs.

Between the 4th and 6th months, rapid growth of the pulmonary vascular system is observed.

In fetuses at 7 months, the lung tissue acquires the features of a porous canal structure; the future air spaces are filled with fluid, which is secreted by the cells lining the bronchi.

At 8-9 months of the intrauterine period, further development of the functional units of the lungs occurs.

The birth of a child requires the immediate functioning of the lungs; during this period, with the onset of breathing, significant changes occur in the airways, especially the respiratory part of the lungs. The formation of the respiratory surface in individual parts of the lungs occurs unevenly. For the management of the respiratory apparatus of the lungs, the condition and readiness of the surfactant film lining the lung surface are of great importance. Violation of the surface tension of the surfactant system leads to serious illnesses in young children.

In the first months of life, the child maintains the ratio of the length and width of the airways, like a fetus, when the trachea and bronchi are shorter and wider than in adults, and the small bronchi are narrower.

The pleura covering the lungs in a newborn baby is thicker, looser, contains villi and outgrowths, especially in the interlobar grooves. Pathological foci appear in these areas. Before the birth of a child, the lungs are prepared to perform the respiratory function, but individual components are in the development stage, the formation and maturation of the alveoli is rapidly proceeding, the small lumen of the muscular arteries is being reconstructed and the barrier function is being eliminated.

After three months of age, period II is distinguished.

1. period of intensive growth of the pulmonary lobes (from 3 months to 3 years).
2. final differentiation of the entire bronchopulmonary system (from 3 to 7 years).

Intensive growth of the trachea and bronchi occurs in the 1st–2nd year of life, which slows down in subsequent years, and the small bronchi grow intensively, and the branching angles of the bronchi also increase. The diameter of the alveoli increases, and the respiratory surface of the lungs doubles with age. In children under 8 months, the diameter of the alveoli is 0.06 mm, in 2 years - 0.12 mm, in 6 years - 0.2 mm, in 12 years - 0.25 mm.

In the first years of life, growth and differentiation of lung tissue elements and blood vessels occur. The ratio of the volumes of shares in individual segments is equalized. Already at 6-7 years of age, the lungs are a fully formed organ and are indistinguishable from the lungs of adults.

Features of the child's respiratory tract

The respiratory tract is divided into upper, which includes the nose, paranasal sinuses, pharynx, Eustachian tubes, and lower, which includes the larynx, trachea, bronchi.

The main function of breathing is to conduct air into the lungs, cleanse it of dust particles, and protect the lungs from the harmful effects of bacteria, viruses, and foreign particles. In addition, the airways warm and humidify the inhaled air.

The lungs are represented by small sacs that contain air. They connect with each other. The main function of the lungs is to absorb oxygen from the atmospheric air and release gases into the atmosphere, primarily acid coal.

Breathing mechanism. When inhaling, the diaphragm and chest muscles contract. Exhalation in older age occurs passively under the influence of elastic traction of the lungs. With bronchial obstruction, emphysema, and also in newborns, active inhalation occurs.

Normally, breathing is established at a frequency at which the volume of breathing is performed due to the minimum energy expenditure of the respiratory muscles. In newborn children, the respiratory rate is 30-40, in adults - 16-20 per minute.

The main carrier of oxygen is hemoglobin. In the pulmonary capillaries, oxygen binds to hemoglobin, forming oxyhemoglobin. In newborns, fetal hemoglobin predominates. On the first day of life, it is contained in the body about 70%, by the end of the 2nd week - 50%. Fetal hemoglobin has the ability to easily bind oxygen and difficult to release it to tissues. This helps the child in the presence of oxygen starvation.

Transport of carbon dioxide occurs in dissolved form; blood saturation with oxygen affects the content of carbon dioxide.

The respiratory function is closely related to the pulmonary circulation. This is a complex process.

During breathing, autoregulation is noted. When the lung stretches during inhalation, the inhalation center is inhibited, and exhalation is stimulated during exhalation. Deep breathing or forced inflation of the lungs leads to a reflex expansion of the bronchi and increases the tone of the respiratory muscles. When the lungs collapse and are compressed, the bronchi become narrowed.

The medulla oblongata contains the respiratory center, from where commands are sent to the respiratory muscles. The bronchi lengthen when you inhale, and shorten and narrow when you exhale.

The relationship between the functions of breathing and blood circulation appears from the moment the lungs expand during the first breath of a newborn, when both the alveoli and blood vessels expand.

With respiratory diseases in children, respiratory dysfunction and respiratory failure may occur.

Features of the structure of a child's nose

In young children, the nasal passages are short, the nose is flattened due to an insufficiently developed facial skeleton. The nasal passages are narrower, the conchae are thickened. The nasal passages are finally formed only by the age of 4 years. The nasal cavity is relatively small in size. The mucous membrane is very loose and well supplied with blood vessels. The inflammatory process leads to the development of edema and, as a result, a reduction in the lumen of the nasal passages. Mucus often stagnates in the nasal passages. It can dry out, forming crusts.

When the nasal passages close, shortness of breath may occur; during this period, the child cannot suckle at the breast, becomes anxious, abandons the breast, and remains hungry. Children, due to difficulty in nasal breathing, begin to breathe through their mouths, their warming of the incoming air is disrupted and their susceptibility to colds increases.

If nasal breathing is impaired, there is a lack of discrimination of odors. This leads to a disturbance in appetite, as well as a disturbance in the understanding of the external environment. Breathing through the nose is physiological, breathing through the mouth is a sign of nasal disease.

Accessory nasal cavities. The paranasal cavities, or sinuses, as they are called, are limited spaces filled with air. The maxillary (maxillary) sinuses are formed by the age of 7. Ethmoidal - by the age of 12, the frontal is fully formed by the age of 19.

Features of the nasolacrimal duct. The nasolacrimal duct is shorter than in adults, its valves are not sufficiently developed, and the outlet is located close to the corner of the eyelids. Due to these features, the infection quickly spreads from the nose to the conjunctival sac.

Features of the pharynxbaby

The pharynx in young children is relatively wide, the palatine tonsils are poorly developed, which explains the rare cases of sore throat in the first year of life. The tonsils are fully developed by the age of 4-5 years. By the end of the first year of life, almond tissue hyperplasias. But its barrier function at this age is very low. Overgrown almond tissue can be susceptible to infection, which is why diseases such as tonsillitis and adenoiditis occur.

The Eustachian tubes open into the nasopharynx and connect it to the middle ear. If an infection travels from the nasopharynx to the middle ear, otitis media occurs.

Features of the larynxbaby

The larynx in children is funnel-shaped and is an extension of the pharynx. In children, it is located higher than in adults, and has a narrowing in the area of ​​the cricoid cartilage, where the subglottic space is located. The glottis is formed by the vocal cords. They are short and thin, this is responsible for the child’s high, sonorous voice. The diameter of the larynx in a newborn in the area of ​​the subglottic space is 4 mm, at 5-7 years old - 6-7 mm, by 14 years old - 1 cm. Features of the larynx in children are: its narrow lumen, many nerve receptors, easily occurring swelling of the submucosal layer, which can lead to severe breathing problems.

The thyroid cartilages form a more acute angle in boys over 3 years of age; from the age of 10, a typical male larynx is formed.

Features of the tracheababy

The trachea is a continuation of the larynx. It is wide and short, the tracheal frame consists of 14-16 cartilaginous rings, which are connected by a fibrous membrane instead of an elastic end plate in adults. The presence of a large number of muscle fibers in the membrane contributes to changes in its lumen.

Anatomically, the trachea of ​​a newborn is located at the level of the IV cervical vertebra, and in an adult - at the level of the VI-VII cervical vertebra. In children, it gradually descends, as does its bifurcation, which is located in a newborn at the level of the third thoracic vertebra, in children 12 years old - at the level of the V-VI thoracic vertebra.

During physiological breathing, the lumen of the trachea changes. During coughing, it decreases by 1/3 of its transverse and longitudinal dimensions. The mucous membrane of the trachea is rich in glands that secrete a secretion that covers the surface of the trachea with a layer 5 microns thick.

The ciliated epithelium promotes the movement of mucus at a speed of 10-15 mm/min from the inside to the outside.

Features of the trachea in children contribute to the development of its inflammation - tracheitis, which is accompanied by a rough, low-timbre cough, reminiscent of a cough “like in a barrel”.

Features of the child's bronchial tree

The bronchi in children are formed at birth. Their mucous membrane is richly supplied with blood vessels and is covered with a layer of mucus, which moves at a speed of 0.25-1 cm/min. A feature of the bronchi in children is that elastic and muscle fibers are poorly developed.

The bronchial tree branches to the bronchi of the 21st order. With age, the number of branches and their distribution remain constant. The size of the bronchi changes rapidly in the first year of life and during puberty. They are based on cartilaginous semirings in early childhood. Bronchial cartilage is very elastic, pliable, soft and easily displaced. The right bronchus is wider than the left and is a continuation of the trachea, so foreign bodies are more often found in it.

After the birth of a child, a columnar epithelium with a ciliated apparatus is formed in the bronchi. With hyperemia of the bronchi and their swelling, their lumen sharply decreases (up to its complete closure).

Underdevelopment of the respiratory muscles contributes to a weak cough impulse in a small child, which can lead to blockage of small bronchi with mucus, and this, in turn, leads to infection of the lung tissue and disruption of the cleansing drainage function of the bronchi.

With age, as the bronchi grow, wide lumens of the bronchi appear, and the bronchial glands produce less viscous secretions, acute diseases of the bronchopulmonary system are less common compared to children of younger ages.

Features of the lungsin children

The lungs in children, as in adults, are divided into lobes, and lobes into segments. The lungs have a lobular structure, the segments in the lungs are separated from each other by narrow grooves and partitions of connective tissue. The main structural unit is the alveoli. Their number in a newborn is 3 times less than in an adult. Alveoli begin to develop from 4-6 weeks of age, their formation occurs up to 8 years. After 8 years, children’s lungs increase due to their linear size, and at the same time, the respiratory surface of the lungs increases.

The following periods can be distinguished in the development of the lungs:

1) from birth to 2 years, when intensive growth of the alveoli occurs;

2) from 2 to 5 years, when elastic tissue intensively develops, bronchi with peribronchial inclusions of lung tissue are formed;

3) from 5 to 7 years, the functional abilities of the lungs are finally formed;

4) from 7 to 12 years, when a further increase in lung mass occurs due to the maturation of lung tissue.

Anatomically, the right lung consists of three lobes (upper, middle and lower). By 2 years, the sizes of the individual lobes correspond to each other, like in an adult.

In addition to the lobar division, segmental division is distinguished in the lungs: in the right lung there are 10 segments, in the left - 9.

The main function of the lungs is breathing. It is believed that 10,000 liters of air pass through the lungs daily. Oxygen absorbed from the inhaled air ensures the functioning of many organs and systems; the lungs take part in all types of metabolism.

The respiratory function of the lungs is carried out with the help of a biologically active substance - surfactant, which also has a bactericidal effect, preventing fluid from entering the pulmonary alveoli.

The lungs remove waste gases from the body.

A feature of the lungs in children is the immaturity of the alveoli; they have a small volume. This is compensated by increased breathing: the younger the child, the more shallow his breathing. The respiratory rate in a newborn is 60, in a teenager it is already 16-18 respiratory movements per minute. Lung development is completed by age 20.

A variety of diseases can impair the vital function of breathing in children. Due to the characteristics of aeration, drainage function and evacuation of secretions from the lungs, the inflammatory process is often localized in the lower lobe. This occurs in a supine state in infants due to insufficient drainage function. Paravisceral pneumonia most often occurs in the second segment of the upper lobe, as well as in the basal-posterior segment of the lower lobe. The middle lobe of the right lung may often be affected.

The following studies are of greatest diagnostic importance: X-ray, bronchological, determination of blood gas composition, blood pH, study of external respiration function, study of bronchial secretions, computed tomography.

By the frequency of breathing and its relationship with the pulse, the presence or absence of respiratory failure is judged (see Table 14).