The child's first breath causes it to occur. Transition to independent breathing of the newborn. Expansion of the lungs after birth

As is known, the formation of respiratory function in newborns is the most weak link in the system of its general adaptation to the extrauterine transition of life. Lungs that have collapsed at birth always pose a potential danger of incomplete or untimely expansion, even during seemingly normal labor.

The adaptation of circulatory function, which ends with the beginning of the functioning of the pulmonary circulation, also depends on the timely onset of spontaneous breathing and adequate expansion of the lungs.

The respiratory cycle, consisting of rhythmically repeating acts of inhalation and exhalation, ensures gas exchange in the lungs and represents coordinated contractions respiratory muscles chest and diaphragm. At the same time, it is important to know what exactly in newborns diaphragmatic breathing plays a decisive role in ensuring respiratory cycles, and, consequently, in the formation of respiratory function in general.

The chest muscles and other respiratory muscles are less prepared and less trained for such physical activity like a cyclic act of breathing. However, in the assessment functional system breathing in newborns should be based on the formation at the time of birth of sufficiently reliable mechanisms that ensure the timely onset of the function of the respiratory center and gas exchange. The physiological mechanisms that ensure the onset of breathing in newborns turn out to be untenable only in the case of some severe pathology leading to a breakdown and disruption of adaptive reactions.

The basic mechanisms of the respiratory function triggering system are innate. They develop in the prenatal period and reach a certain stage of maturity by the time of birth. Already by 28-33 weeks. pregnancy, the fetus is capable of independent breathing a certain time, while acquiring a relatively stable breathing rhythm.

During full-term pregnancy, the respiratory system healthy fetus turns out to be so mature that it ensures the spontaneous and timely onset of adequate respiratory and gas exchange functions and its further maintenance.

In terms of providing resuscitation care knowledge becomes important physiological mechanisms the newborn's first breath. It is known that ligation of the umbilical cord entails the cessation of oxygen supply to the fetus and the accumulation of carbon dioxide in its tissues. This gave rise to a seemingly logical assumption that a change in the gas composition of the blood and, in particular, the accumulation of carbon dioxide (a physiological stimulant of respiration) is the cause of the first inhalation. In addition, the resulting fetal hypoxia and the body’s natural need for oxygen ensure the beginning of the formation of respiratory function (E.L. Golubeva, 1966).

According to other authors, the main reason for the occurrence of the first breath is the excitation of the chemoreceptors of the carotid glomerulus of the aortic arch in response to hypoxemia, followed by excitation of the respiratory center by excessive accumulation of CO2 as the main mechanism of regulation of the respiratory system.

According to E. L. Golubeva (1966), the mechanism of the first breath is associated with the total effect of physical and chemical stimuli that cause a flow of peripheral impulses into the reticular formation of the brain stem and, first of all, the middle and medulla oblongata. At the moment of birth of a child, he immediately receives a whole complex of sensory stimulation (differences in temperature, pressure in the uterus and outside it, changes in body position, mechanical and other irritations). Umbilical cord ligation leads to sharp fall oxygen tension in the blood and increased carbon dioxide. As a result of the flow of impulses into various parts of the central nervous system and spinal cord selectively sharply increases the excitability of the reticular formation, and then the respiratory “system” medulla oblongata(breathing center).

According to E.L. Golubeva and A.I. Arshavsky (1960), who specifically studied this issue, it is the reticular formation of the midbrain with subsequent excitation of the respiratory center that is the main trigger that triggers the mechanism of the first breath. At the same time, the activating effect reticular formation on the breathing center manifests itself only under conditions of its certain readiness for the beginning of “rhythmic excitation,” which is determined by the maturity of the newborn. After the first entry, the final formation of the respiratory function begins according to the principle: once the “swing of the pendulum” has arisen, it continues continuously, supported by the influence of a whole complex of physiological irritants.

From the moment of the first breath and the establishment of respiratory excursions of the chest into airways air enters, the “atelectatic” lungs quickly expand, capillaries open, and pulmonary blood flow begins. From this moment on, the pulmonary circulation functions. At the same time, the botal duct and foramen ovale gradually close interatrial septum, the system of the left and right heart begins to function separately.

As the lungs expand and the pulmonary circulation is turned on, a unified system of alveolar-capillary blood flow arises, which determines the adequacy of gas exchange. The opening of the alveoli and pulmonary capillaries creates a flow of interoreceptive impulses along parasympathetic innervation and other afferent pathways into various parts of the central nervous system and mainly into respiratory center. From the central nervous system, impulses travel through afferent fibers through the spinal centers to the respiratory muscles, which determines the rhythm and depth breathing excursions. This is how it arises reflex arc, providing physiological regulation of respiratory function (I. D. Arshavsky, 1960; L. S. Persianinov, 1962).

As the newborn adapts to intrauterine life, already in the first 40-60 minutes after birth, he has a normal breathing rhythm, its frequency fluctuates between 40-50 per minute. At the same time, gas exchange indicators are established in the following parameters: oxygen tension (pO2) in mixed capillary blood fluctuates between 60-80 mm pg. Art., carbon dioxide tension (pCO2) 30-45 mm Hg. Art., pH within 7.3-7.4; base excess (EB) -4.-8 mmol/l of blood, buffer bases (<8В) 36,8- 39,5 ммоль/л плазмы, стандартный бикарбонат (5В) 12- 14 мэкв/л плазмы, истинный бикарбонат 13,5-14,5 ммоль/л плазмы. Указанные параметры газообмена и КЩС характери­зуются закономерными колебаниями, так как становление функции дыхания у новорожденных в течение первого часа также отличается большими индивидуальными особенностями. Важно, что именно к этому периоду наступает так называемая первичная стабилизация показателей газообмена с последующей окончательной нормализацией их на протяжении дальнейшего периода новорожденности.

External respiration parameters are also very variable. For example, tidal volume varies from 15 to 25 ml (on average 20±5 ml), minute breathing volume ranges from 400-800 ml (on average 500±50 ml) (G. Kesler et al., 1968).

As can be seen, in the first 30-40 minutes, the respiratory function in newborns is characterized by large fluctuations in the main parameters of external respiration and gas exchange. This indicates their intensive restructuring in conditions of extrauterine life and adaptation during the transition to pulmonary breathing.

The cardiovascular system of a newborn has significantly greater compensatory capabilities.

Systolic pressure during the first hour of life fluctuates between 55-60 mmHg. Art., diastolic 40-30 mm Hg. Art., the heart rate is set within 130-140 per minute. Subsequently, blood pressure gradually increases and the heart rate decreases.

It is known that newborns have a high hematocrit value. It fluctuates between 55-60% and even higher. This is explained by the high content of hemoglobin (up to 18-20 g%), red blood cells (5.5-6.2 million/mm3), leukocytes (25,000-29,000 per mm3) and other formed elements, blood. Increased levels of hemoglobin and red blood cells determine a high oxygen capacity of the blood, which has an important adaptive value in the process of adaptation of a newborn to extrauterine life in the first hours and days of life after birth. For stable adaptation of circulatory function, volumetric indicators of the mass of blood and its components are important. For example, with a newborn weighing from 3000 to 4000 g, the BCC ranges from 330-360 ml (98-96 ml/kg), BCC-148-175 ml (46.6-46.1 ml/kg), BCC-171 .8-190.6 (51.7-50.1 ml/kg). These values ​​are also variable, which depends on a number of reasons (method of delivery, course of pregnancy, presence of anemia in the mother, etc.).

With a premature fetus, intrauterine hypoxia, malnutrition, complicated labor and for a number of other reasons, a newborn may be born in a state of general depression, apnea, or severe asphyxia. In these cases, the viability of the child depends on the timely provision of resuscitation care to its full extent.

Consequently, there is a need for the doctor to quickly orient himself in the severity of asphyxia, which in turn determines the optimal volume of resuscitation care.

Emergency care in obstetrics and gynecology, L.S. Persianinov, N.N. Rasstrigin, 1983

The first breath of a newborn occurs through this mechanism - intermittent compression of the chest during vaginal delivery facilitates the removal of fetal fluid from the lungs. Surfactant in the mucous layer lining the alveoli, reducing surface tension and the pressure necessary to open the alveoli, facilitates lung aeration.

Despite this, the pressure required to fill the lungs with air during a newborn's first breath is higher than when inhaling at any other age. It ranges from 10 to 50 cm of water. Art. and usually amounts to 10-20 cm of water. Art., while during subsequent breaths in healthy newborns and adults it is about 4 cm of water. Art. This is due to the need to overcome the surface tension forces during the first breath (especially in the small branches of the bronchi), the viscosity of the liquid remaining in the respiratory tract and the entry of approximately 50 ml of air into the lungs, 20-30 ml of which remain in the lungs, forming the FRC. Most of the fetal fluid from the lungs is absorbed into the pulmonary bloodstream, which increases many times over as the entire output of the right ventricle is directed into the pulmonary vasculature. Residual fetal fluid is released through the upper respiratory tract and swallowed, and sometimes re-enters the respiratory tract from the oropharynx. The mechanism for removing fluid is disrupted during cesarean section or due to damage to the endothelium, hypoalbuminemia, increased venous pressure in the lungs, and the entry of sedatives into the blood of the newborn.

The triggering factors for a newborn's first breath are numerous. What is the contribution of each of them is unknown. These include a decrease in Po2 and pH and an increase in Pco2 due to cessation of placental circulation, redistribution of cardiac output after clamping of the umbilical cord vessels, a decrease in body temperature, and various tactile stimuli.

Low birth weight babies have much more flexible lungs than full-term babies, making the newborn's first breath more difficult. FRC in very premature infants is the lowest due to the presence of atelectasis. Disturbances in the ventilation-perfusion relationship are most pronounced and lasting when air cavities form like air traps. As a result of atelectasis, intrapulmonary shunting and hypoventilation, hypoxemia (Pao2 50-60 mm Hg) and hypercapnia develop. The most profound gas exchange disturbances, similar to those in hyaline membrane disease, are observed in children with extremely low birth weight.

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It is known that respiratory movements in the fetus occur in the 13th week of the intrauterine period. However, they occur when the glottis is closed. During childbirth, transplacental blood circulation is disrupted, and when the umbilical cord is clamped in a newborn, its complete cessation occurs, which causes a significant decrease in the partial pressure of oxygen (pO2), an increase in pCO2, and a decrease in pH. In this regard, an impulse arises from the receptors of the aorta and carotid artery to the respiratory center, as well as a change in the corresponding parameters of the environment around the respiratory center itself. For example, in a healthy newborn child, pO 2 decreases from 80 to 15 mm Hg. Art., pCO 2 increases from 40 to 70 mm Hg. Art., and the pH drops below 7.35. Along with this, irritation of skin receptors is also important. A sharp change in temperature and humidity due to the transition from the intrauterine environment to being in the air atmosphere in the room is an additional impulse for the respiratory center. Tactile reception is probably of less importance when passing through the birth canal and during delivery of the newborn.

Contraction of the diaphragm creates negative intrathoracic pressure, which facilitates the entry of air into the airways. More significant resistance to the inhaled air is provided by the surface tension in the alveoli and the viscosity of the fluid in the lungs. Surface tension forces in the alveoli are reduced by surfactant. Lung fluid is quickly absorbed by lymphatic vessels and blood capillaries if normal expansion of the lung occurs. It is believed that normally negative intrapulmonary pressure reaches 80 cm of water. Art., and the volume of inhaled air during the first breath is more than 80 ml, which is significantly higher than the residual volume.

Regulation of breathing is carried out by the respiratory center located in the reticular formation of the brain stem in the area of ​​the bottom of the fourth ventricle. The respiratory center consists of three parts: the medullary, which begins and maintains the alternation of inhalation and exhalation; apneic, which causes a prolonged inspiratory spasm (located at the level of the middle and lower part of the pons); pneumotaxic, which has an inhibitory effect on the apneic part (located at the level of the upper part of the pons).

Regulation of respiration is carried out by central and peripheral chemoreceptors, and central chemoreceptors are the main ones (80%) in the regulation of respiration. Central chemoreceptors are more sensitive to changes in pH, and their main function is to maintain the constancy of H + ions in the cerebrospinal fluid. CO 2 diffuses freely across the blood-brain barrier. An increase in H+ concentration in the cerebrospinal fluid stimulates ventilation. Peripheral chemo- and baroreceptors, especially carotid and aortic ones, are sensitive to changes in oxygen and carbon dioxide levels. They are functionally active before the birth of the child.

At the same time, the pneumotaxic part of the respiratory center matures only during the first year of life, which explains the pronounced arrhythmia of breathing. Apnea is most frequent and prolonged in premature infants, and the lower the body weight, the more frequent and prolonged the apnea. This indicates insufficient maturity of the pneumotaxic part of the respiratory center. But even more important in predicting the survival of premature babies is the rapidly increasing increase in breathing in the first minutes of a newborn’s life. This is evidence of insufficient development of the apneic part of the respiratory center.

During the prenatal period, the lungs are not the organ of external respiration of the fetus; this function is performed by the placenta. But long before birth, breathing movements appear, which are necessary for the normal development of the lungs. The lungs are filled with liquid (about 100 ml) before ventilation begins.

Birth causes sudden changes in the state of the respiratory center, leading to the onset of ventilation. The first breath occurs 15-70 seconds after birth, usually after clamping the umbilical cord, sometimes before it, i.e. immediately after birth.

Factors stimulating the first breath:

The presence of humoral respiratory irritants in the blood: CO 2, H + and lack of O 2. During childbirth, especially after ligation of the umbilical cord, CO 2 tension and H + concentration increase, and hypoxia intensifies. But hypercapnia, acidosis and hypoxia themselves do not explain the onset of the first breath. It is possible that in newborns, low levels of hypoxia can excite the respiratory center, acting directly on brain tissue.

An equally important factor stimulating the first breath is a sharp increase in the flow of afferent impulses from skin receptors (cold, tactile), proprioceptors, vestibuloreceptors, which occurs during childbirth and immediately after birth. These impulses activate the reticular formation of the brain stem, which increases the excitability of the neurons of the respiratory center.

The stimulating factor is the elimination of sources of inhibition of the respiratory center. Irritation of the receptors located in the nostril area by the liquid greatly inhibits breathing (the “diver’s” reflex). Therefore, immediately at the birth of the fetal head from the birth canal, obstetricians remove mucus and amniotic fluid from the airways.

Thus, the occurrence of the first breath is the result of the simultaneous action of a number of factors.

The first breath of a newborn is characterized by strong excitation of the inspiratory muscles, especially the diaphragm. In 85% of cases, the first breath is deeper, and the first respiratory cycle is longer than subsequent respiratory cycles. There is a strong decrease in intrapleural pressure. This is necessary to overcome the frictional force between the liquid in the airways and their wall, as well as to overcome the surface tension of the alveoli at the liquid-air interface after air enters them. The duration of the first inhalation is 0.1–0.4 seconds, and the exhalation is on average 3.8 seconds. Exhalation occurs against the background of a narrowed glottis and is accompanied by a cry. The volume of exhaled air is less than that of inhaled air, which ensures the beginning of the formation of FRC. FRC increases from inspiration to inspiration. Aeration of the lungs usually ends by 2-4 days after birth. FRC at this age is about 100 ml. With the beginning of aeration, the pulmonary circulation begins to function. The fluid remaining in the alveoli is absorbed into the bloodstream and lymph.

In newborns, the ribs are positioned at a lesser angle than in adults, so contractions of the intercostal muscles are less effective in changing the volume of the thoracic cavity. Quiet breathing in newborns is diaphragmatic; inspiratory muscles work only when crying and shortness of breath.

Newborns always breathe through their nose. The respiratory rate shortly after birth averages about 40 per minute. The airways in newborns are narrow, their aerodynamic resistance is 8 times higher than in adults. The lungs have little extensibility, but the compliance of the walls of the chest cavity is high, which results in low values ​​of elastic traction of the lungs. Newborns are characterized by a relatively small inspiratory reserve volume and a relatively large expiratory reserve volume. The breathing of newborns is irregular, a series of rapid breathing alternates with more rare breathing, deep sighs occur 1-2 times per minute. Breathing may be held during exhalation (apnea) for up to 3 seconds or more. Premature newborns may experience Cheyne-Stokes breathing. The activity of the respiratory center is coordinated with the activity of the centers of sucking and swallowing. When feeding, the breathing rate usually corresponds to the frequency of sucking movements.

Age-related changes in breathing:

After birth, until the age of 7-8 years, the processes of differentiation of the bronchial tree and an increase in the number of alveoli occur (especially in the first three years). During adolescence, the volume of the alveoli increases.

Minute breathing volume increases with age by almost 10 times. But children in general are characterized by a high level of pulmonary ventilation per unit of body weight (relative MVR). Respiratory rate decreases with age, especially strongly during the first year after birth. With age, the breathing rhythm becomes more stable. In children, the duration of inhalation and exhalation is almost equal. An increase in the duration of exhalation in most people occurs during adolescence.

With age, the activity of the respiratory center improves, and mechanisms develop that ensure a clear change in respiratory phases. Children's ability to voluntarily regulate breathing gradually develops. From the end of the first year of life, breathing is involved in speech function.

8.7. RESEARCH OF METABOLISM AND ENERGY CONVERSION IN THE BODY

Metabolism in the body is interconnected with the transformation of energy. The potential energy of complex organic compounds supplied with food is converted into thermal, mechanical and electrical energy. Energy is spent not only on maintaining body temperature and performing work, but also on recreating the structural elements of cells, ensuring their vital activity, growth and development of the body.

Heat generation in the body is of a 2-phase nature. During the oxidation of proteins, fats and carbohydrates, most of the energy is converted into heat (primary heat), and less is used for the synthesis of ATP, i.e. for accumulation in high-energy connections. During the oxidation of carbohydrates, 77.3% of the energy of the chemical bond of glucose is dissipated in the form of heat, and 22.7% goes to the synthesis of ATP. The energy accumulated in ATP is further used for mechanical work, electrical processes, and ultimately also turns into heat (secondary heat). Thus, the amount of heat generated in the body is a measure of the total energy of chemical bonds that have undergone biological oxidation. The energy produced in the body can be expressed in heat units - calories or joules.

To study the processes of energy formation in the body, the following are used: direct calorimetry, indirect calorimetry and the study of gross metabolism.

Direct calorimetry is based on direct accounting of the heat generated by the body. A biocalorimeter is a sealed and well-insulated chamber from the external environment, into which O 2 is supplied and excess CO 2 and vapors are absorbed. Water circulates through tubes. The heat generated by a person or animal in the chamber heats the circulating water, which makes it possible to calculate the amount of heat generated by the organism under study based on the amount of flowing water and the change in its temperature.

Because heat generation in the body is ensured by oxidative processes, it is possible indirect calorimetry, i.e. indirect, indirect determination of heat generation by gas exchange - accounting for consumed O 2 and released CO 2 with subsequent calculation of heat production.

For long-term studies of gas exchange, special respiratory chambers (closed methods of indirect calorimetry) are used - for example, the Shaternikov respiratory apparatus. Short-term determination of gas exchange is carried out using non-chamber methods (open methods of indirect calorimetry).

The most common is the Douglas-Haldane method. Within a few minutes, the exhaled air is collected in a bag made of airtight fabric (Douglas bag). Then the volume of exhaled air is measured and the amount of O 2 and CO 2 in it is determined.

The respiratory coefficient (RC) is the ratio of the volume of CO 2 released to the volume of O 2 absorbed.

DC during the oxidation of carbohydrates, proteins and fats is different. The oxidation of 1 g of each of these substances requires a different amount of O 2 and is accompanied by the release of different amounts of heat.

During the oxidation of carbohydrates DC = 1. For example, the result of glucose oxidation: C 6 H 12 O 6 + 6O 2 = 6CO 2 + 6H 2 O. The number of molecules of CO 2 formed is equal to the number of molecules of O 2 expended. And an equal number of gas molecules, at the same temperature and the same pressure, occupy the same volume (Avogadro-Gerard law).

For protein oxidation DC = 0.8; fat DC = 0.7. When a person is on a mixed diet under standard conditions, DC = 0.85 - 0.86.

Caloric equivalent of oxygen(CEC) or caloric cost of oxygen is the amount of heat released by the body after consuming 1 liter of oxygen.

This indicator depends on the DC and is determined using special tables, where each DC value corresponds to a certain value of the caloric cost of oxygen. For example: DC=0.8; KS=4.801 kcal. DC=0.9; KS=4.924.

Thus, gas analysis data are converted into thermal units.

After determining the volume of oxygen consumed per unit of time (day, hour, minute), it becomes possible to determine the amount of heat released by the body during this time (EK, multiplied by the volume of oxygen consumed).

During work, DC increases and in most cases approaches 1. This is explained by the fact that during intense muscular work the main source of energy is the oxidation of carbohydrates. After completion of the work, the DC first increases, then sharply decreases, and only after 30-50 minutes does it return to normal. These changes in DC after work do not reflect the true relationship between the oxygen currently used and the CO 2 released.

At the beginning of the recovery period, DC increases due to the fact that during work lactic acid accumulates in the muscles, for the oxidation of which there was not enough oxygen (oxygen debt). Lactic acid enters the blood and displaces CO 2 from bicarbonates, attaching bases. Due to this, the amount of CO 2 released becomes greater than the amount of CO 2 currently formed in the tissues.

The opposite picture is observed later, when lactic acid gradually disappears from the blood. One part of it is oxidized, the other is resynthesized into glycogen, and the third is excreted in sweat and urine. As the amount of lactic acid decreases, bases are released. Bases bind CO 2 and form bicarbonates. Therefore, DC falls due to retention of CO 2 in the blood coming from the tissues.

Study gross exchange- this is a long-term (over the course of a day) determination of gas exchange, which makes it possible not only to find the heat production of the body, but also to resolve the question of which substances were generated due to the oxidation. To do this, in addition to the oxygen used and CO 2 released, nitrogen (1 g of nitrogen is contained in 6.25 g of protein) and carbon (proteins contain approximately 53% carbon) excreted in the urine are determined.

BX(OO) is an indicator that reflects the level of energy processes under standard conditions, which are as close as possible to the state of functional rest of the body.

Energy expenditure under OO conditions is associated with maintaining the minimum level of oxidative processes necessary for cell life and with the activity of constantly working organs and systems - respiratory muscles, heart, kidneys, liver, and maintaining muscle tone. The release of thermal energy during these processes provides the heat production necessary to maintain body temperature.

5 conditions for defining an OO.

Time. The study is carried out in the morning before 9 hours after sleep.

On an empty stomach (12-16 hours after eating), since the intake and action of food causes an intensification of energy processes (specific dynamic action of food). SDDP persists for several hours. With protein foods, metabolism increases by 30%, with fats and carbohydrates by 14-15%.

Comfort temperature in the room: 18-20 degrees C. (temperature, barometric pressure, air humidity, etc. can affect the intensity of oxidative processes).

The study is carried out lying down, i.e. in a state of muscle rest.

The use of pharmacological drugs that affect energy processes, as well as narcotic substances, is preliminarily excluded.

Under these conditions, in a healthy person, OO ranges from 1600 to 1800 kcal per day, depending on: 1. Age, 2. Gender, 3 Body mass (weight), 4. Height.

OO formulas and tables are the average data of a large number of healthy people studied of different gender, age, body weight and height. Allowable fluctuations are 10%.

Disproportionately high values ​​of OO are observed with excessive thyroid function. A decrease in OO occurs with insufficiency of the thyroid gland (myxedema), pituitary gland, and gonads.

The intensity of OO, calculated per 1 kg of body weight, is significantly higher in children than in adults. The value of OO of a person aged 20-40 years remains at a fairly constant level. In old age, OO decreases.

Surface rule– energy expenditure by warm-blooded animals is proportional to the surface of the body.

If we recalculate the intensity of OO per 1 kg of body weight, it turns out that in different species of animals and even in people with different body weights and heights, this indicator varies greatly. If we recalculate the intensity of RO per 1 m 2 of body surface, then the results obtained do not differ so sharply.

This rule is relative. In two individuals with the same body surface area, metabolism can differ significantly. The level of oxidative processes is determined not so much by heat transfer from the surface of the body, but by heat production, depending on the biological characteristics of the animal species and the state of the body, which is determined by the activity of the nervous, endocrine and other systems.

Energy exchange during physical labor.

Muscular work significantly increases energy consumption, so daily energy consumption significantly exceeds the OO value. This increase constitutes a work increase. The more intense the muscle work, the greater it is.

The degree of energy expenditure during various physical activities is determined by the physical activity coefficient (PFA). CFA is the ratio of total energy consumption per day to the value of OO. According to this principle, 5 groups are distinguished:

Mental work causes an insignificant (2-3%) increase in energy expenditure compared to complete rest, if not accompanied by movement. However, physical activity and emotional arousal increase energy costs (experienced emotional arousal can cause an increase in metabolism by 11-19% over several days).

Daily energy expenditure in children and adolescents depends on age:

6 months - 1 g - 800 kcal

1 – 1.5 g - 1300

1,5 – 2 - 1500

14 – 17 (boys) – 3150

13 - 17 (girls) – 2750.

By the age of 80, energy consumption decreases (2000-2200 kcal).

The mechanism of the first breath of a newborn.

Surfactant is necessary for the start of breathing when a baby is born. Before birth, the lungs are in a collapsed state. After birth, the child makes several strong breathing movements, the lungs expand, and the surfactant keeps them from collapsing (collapse). Lack or defects of surfactant cause severe illness (respiratory distress syndrome). The surface tension in the lungs of such children is high, so many alveoli are in a collapsed state.

#85 Describe the nodal mechanisms of the functional system that maintains the optimal blood gas composition for metabolism.

Impulses coming from central and peripheral chemoreceptors are a necessary condition for the periodic activity of the neurons of the respiratory center and the correspondence of ventilation of the lungs to the gas composition of the blood. The latter is a rigid constant of the internal environment of the body and is maintained on the principle of self-regulation through the formation functional respiratory system. The system-forming factor of this system is the blood gas constant. Any changes in it are stimuli for excitation of receptors located in the alveoli of the lungs, in blood vessels, in internal organs, etc. Information from the receptors enters the central nervous system, where it is analyzed and synthesized, on the basis of which reaction apparatuses are formed. Their combined activity leads to the restoration of the blood gas constant. The process of restoring this constant includes not only the respiratory organs (especially those responsible for changes in the depth and frequency of breathing), but also the circulatory organs, excretions and others, which together represent the internal link of self-regulation. If necessary, an external link is also included in the form of certain behavioral reactions aimed at achieving an overall beneficial result - restoration of the blood gas constant.