Maximum expiratory volume. Tidal volume and minute volume (MOD), respiratory equivalent

For a freediver, the lungs are the main "working tool" (of course, after the brain), so it is important for us to understand the structure of the lungs and the whole process of breathing. Usually, when we talk about respiration, we mean external respiration or ventilation of the lungs - the only process in the respiratory chain that we notice. And consider breathing should begin with it.

The structure of the lungs and chest

The lungs are a porous organ, similar to a sponge, resembling in its structure an accumulation of individual bubbles or a bunch of grapes with a large number of berries. Each "berry" is a pulmonary alveolus (pulmonary vesicle) - a place where the main function of the lungs is performed - gas exchange. Between the air of the alveoli and the blood lies an air-blood barrier formed by very thin walls of the alveoli and the blood capillary. It is through this barrier that diffusion of gases occurs: oxygen enters the blood from the alveoli, and carbon dioxide enters the alveolus from the blood.

Air enters the alveoli through the airways - trochea, bronchi and smaller bronchioles, which end in alveolar sacs. The branching of the bronchi and bronchioles forms lobes (the right lung has 3 lobes, the left has 2 lobes). On average, in both lungs there are about 500-700 million alveoli, the respiratory surface of which ranges from 40 m 2 when exhaling to 120 m 2 when inhaling. In this case, a greater number of alveoli are located in the lower sections of the lungs.

The bronchi and trachea have a cartilaginous base in their walls and are therefore quite rigid. Bronchioles and alveoli are soft-walled and therefore can collapse, that is, stick together like a deflated balloon, if some air pressure is not maintained in them. To prevent this from happening, the lungs, as a single organ, are covered on all sides with a pleura - a strong hermetic membrane.

The pleura has two layers - two leaves. One leaf is tightly attached to the inner surface of a rigid chest, the other - surrounds the lungs. Between them is the pleural cavity, which maintains negative pressure. Due to this, the lungs are in a straightened state. Negative pressure in the pleural space is due to the elastic recoil of the lungs, that is, the constant desire of the lungs to reduce their volume.

The elastic recoil of the lungs is due to three factors:
1) the elasticity of the tissue of the walls of the alveoli due to the presence of elastic fibers in them
2) bronchial muscle tone
3) surface tension of the liquid film covering the inner surface of the alveoli.

The rigid frame of the chest is made up of ribs, which are flexible, thanks to cartilage and joints, attached to the spine and joints. Due to this, the chest increases and decreases in volume, while maintaining the rigidity necessary to protect the organs located in the chest cavity.

In order to inhale air, we need to create a lower pressure in the lungs than atmospheric pressure, and to exhale a higher one. Thus, for inhalation it is necessary to increase the volume of the chest, for exhalation - a decrease in volume. In fact, most of the effort of breathing is spent on inhalation; under normal conditions, exhalation is carried out due to the elastic properties of the lungs.

The main respiratory muscle is the diaphragm - a domed muscular partition between the chest cavity and the abdominal cavity. Conventionally, its boundary can be drawn along the lower edge of the ribs.

When inhaling, the diaphragm contracts and expands active action towards the bottom internal organs. At the same time, incompressible organs abdominal cavity are pushed down and to the sides, stretching the walls of the abdominal cavity. With a quiet breath, the dome of the diaphragm descends by approximately 1.5 cm, and the vertical size of the chest cavity increases accordingly. At the same time, the lower ribs diverge somewhat, increasing the girth of the chest, which is especially noticeable in the lower sections. When exhaling, the diaphragm passively relaxes and is pulled up by the tendons holding it to its calm state.

In addition to the diaphragm, the external oblique intercostal and intercartilaginous muscles also take part in the increase in the volume of the chest. As a result of the rise of the ribs, the displacement of the sternum forward and the departure of the lateral parts of the ribs to the sides increase.

With very deep intensive breathing or with an increase in inhalation resistance, a number of auxiliary respiratory muscles are included in the process of increasing the volume of the chest, which can raise the ribs: scalariform, pectoralis major and minor, serratus anterior. The accessory muscles of inspiration also include the extensor muscles. thoracic region of the spine and fixing the shoulder girdle when resting on arms folded back (trapezoidal, rhomboid, raising the scapula).

As mentioned above, a calm breath proceeds passively, almost against the background of relaxation of the muscles of inspiration. With active intensive exhalation, the muscles “connect” abdominal wall, resulting in a decrease in the volume of the abdominal cavity and an increase in pressure in it. The pressure is transferred to the diaphragm and raises it. Due to the reduction the internal oblique intercostal muscles lower the ribs and bring their edges closer.

Breathing movements

AT ordinary life, observing yourself and your friends, you can see both breathing, provided mainly by the diaphragm, and breathing, provided mainly by the work of the intercostal muscles. And this is within the normal range. The muscles of the shoulder girdle are more often connected when serious illnesses or intensive work, but almost never - in relatively healthy people in a normal state.

It is believed that breathing, provided mainly by the movements of the diaphragm, is more typical for men. Normally, inhalation is accompanied by a slight protrusion of the abdominal wall, exhalation by its slight retraction. This is abdominal breathing.

In women, the chest type of breathing is most common, provided mainly by the work of the intercostal muscles. This may be due to the biological readiness of a woman for motherhood and, as a result, with difficulty in abdominal breathing during pregnancy. With this type of breathing, the most noticeable movements are made by the sternum and ribs.

Breathing, in which the shoulders and collarbones actively move, is provided by the work of the muscles of the shoulder girdle. Ventilation of the lungs in this case is ineffective and concerns only the tops of the lungs. Therefore, this type of breathing is called apical. Under normal conditions, this type of breathing practically does not occur and is used either during certain gymnastics or develops with serious diseases.

In freediving, we believe that abdominal or belly breathing is the most natural and productive type of breathing. The same is said in yoga and pranayama.

Firstly, because there are more alveoli in the lower lobes of the lungs. Secondly, respiratory movements are connected to our autonomic nervous system. Belly breathing activates the parasympathetic nervous system - the brake pedal for the body. chest breathing activates the sympathetic nervous system - the gas pedal. With active and long apical breathing, restimulation of the sympathetic nervous system. This works both ways. So panicking people always breathe apical breathing. And vice versa, if you breathe calmly with your stomach for some time, the nervous system calms down and all processes slow down.

lung volumes

During quiet breathing, a person inhales and exhales about 500 ml (from 300 to 800 ml) of air, this volume of air is called tidal volume. In addition to the usual tidal volume, with the deepest breath a person can inhale another approximately 3000 ml of air - this is inspiratory reserve volume. After a normal calm exhalation, an ordinary healthy person is able to “squeeze out” about 1300 ml of air from the lungs with the tension of the exhalation muscles - this is expiratory reserve volume.

The sum of these volumes is vital capacity (VC): 500 ml + 3000 ml + 1300 ml = 4800 ml.

As you can see, nature has prepared for us almost a tenfold supply of the possibility of "pumping" air through the lungs.

Tidal volume is a quantitative expression of the depth of breathing. The vital capacity of the lungs is the maximum volume of air that can be brought in or out of the lungs during one inhalation or exhalation. The average vital capacity of the lungs in men is 4000 - 5500 ml, in women - 3000 - 4500 ml. Physical training and various chest stretches can increase VC.

After maximum deep exhalation, about 1200 ml of air remains in the lungs. It - residual volume. Most of it can be removed from the lungs only with an open pneumothorax.

The residual volume is determined primarily by the elasticity of the diaphragm and intercostal muscles. Increasing the mobility of the chest and reducing the residual volume is an important task in preparing for diving to great depths. Dives below the residual volume for the average untrained person are dives deeper than 30-35 meters. One of the popular ways to increase the elasticity of the diaphragm and reduce the residual volume of the lungs is to regularly perform uddiyana bandha.

The maximum amount of air that can be in the lungs is called total lung capacity, it is equal to the sum of the residual volume and the vital capacity of the lungs (in the example used: 1200 ml + 4800 ml = 6000 ml).

The volume of air in the lungs at the end of a quiet exhalation (with relaxed respiratory muscles) is called functional residual lung capacity. It is equal to the sum of the residual volume and the expiratory reserve volume (in the example used: 1200 ml + 1300 ml = 2500 ml). Functional residual lung capacity is close to the volume of alveolar air before inhalation.

Lung ventilation is determined by the volume of air inhaled or exhaled per unit of time. Usually measured minute volume of breathing. Ventilation of the lungs depends on the depth and frequency of breathing, which at rest ranges from 12 to 18 breaths per minute. The minute volume of breathing is equal to the product of the respiratory volume and the respiratory rate, i.e. about 6-9 liters.

To assess lung volumes, spirometry is used - a method for studying the function of external respiration, which includes the measurement of volumetric and speed indicators of respiration. We recommend this study to anyone who plans to seriously engage in freediving.

Air is not only in the alveoli, but also in the airways. These include the nasal cavity (or mouth with oral breathing), nasopharynx, larynx, trachea, bronchi. The air in the airways (with the exception of the respiratory bronchioles) does not participate in gas exchange. Therefore, the lumen of the airways is called anatomical dead space. When inhaling, the last portions of atmospheric air enter the dead space and, without changing their composition, leave it when exhaling.

The volume of anatomical dead space is about 150 ml, or about 1/3 of the tidal volume during quiet breathing. Those. of 500 ml of inhaled air, only about 350 ml enters the alveoli. In the alveoli at the end of a calm exhalation there is about 2500 ml of air, therefore, with each calm breath, only 1/7 of the alveolar air is renewed.

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Indicators of pulmonary ventilation largely depend on the constitution, physical training, height, body weight, sex and age of a person, so the data obtained must be compared with the so-called proper values. Proper values ​​are calculated according to special nomograms and formulas, which are based on the definition of proper basal metabolism. Many functional research methods have been reduced over time to a certain standard volume.

Measurement of lung volumes

Tidal volume

Tidal volume (TO) is the volume of air inhaled and exhaled during normal breathing, equal to an average of 500 ml (with fluctuations from 300 to 900 ml). About 150 ml of it is the volume of functional dead space air (VFMP) in the larynx, trachea, bronchi, which does not take part in gas exchange. The functional role of the HFMP is that it mixes with the inhaled air, humidifying and warming it.

expiratory reserve volume

The expiratory reserve volume is the volume of air equal to 1500-2000 ml, which a person can exhale if, after a normal exhalation, he makes a maximum exhalation.

Inspiratory reserve volume

Inspiratory reserve volume is the volume of air that a person can inhale if, after a normal inspiration, he takes a maximum breath. Equal 1500 - 2000 ml.

Vital capacity of the lungs

The vital capacity of the lungs (VC) is equal to the sum of the reserve volumes of inhalation and exhalation and the tidal volume (average 3700 ml) and is the volume of air that a person is able to exhale during the deepest exhalation after a maximum inhalation.

Residual volume

Residual volume (VR) is the volume of air that remains in the lungs after maximum exhalation. Equal 1000 - 1500 ml.

Total lung capacity

The total (maximum) lung capacity (TLC) is the sum of respiratory, reserve (inhalation and exhalation) and residual volumes and is 5000 - 6000 ml.

The study of tidal volumes is needed to assess compensation respiratory failure by increasing the depth of breathing (inhalation and exhalation).

Spirography of the lungs

Spirography of the lungs provides the most reliable data. In addition to measuring lung volumes, a spirograph can be used to obtain a number of additional indicators (respiratory and minute ventilation volumes, etc.). The data are recorded in the form of a spirogram, which can be used to judge the norm and pathology.

The study of the intensity of pulmonary ventilation

Minute breathing volume

The minute volume of respiration is determined by multiplying the tidal volume by the respiratory rate, on average it is 5000 ml. More precisely determined by spirography.

Maximum ventilation

Maximum lung ventilation ("breathing limit") is the amount of air that can be ventilated by the lungs at maximum exertion. respiratory system. It is determined by spirometry with the deepest possible breathing with a frequency of about 50 per minute, normally equal to 80 - 200 ml.

Breath reserve

The respiratory reserve reflects the functionality of the human respiratory system. At healthy person equal to 85% of the maximum ventilation of the lungs, and in case of respiratory failure it decreases to 60 - 55% and below.

All these tests make it possible to study the state of pulmonary ventilation, its reserves, the need for which may arise when performing heavy physical work or in case of a respiratory disease.

Study of the mechanics of the respiratory act

This method allows you to determine the ratio of inhalation and exhalation, respiratory effort in different phases of breathing.

EFZHEL

The expiratory forced vital capacity of the lungs (EFZhEL) is examined according to Votchal-Tiffno. It is measured in the same way as when determining VC, but with the most rapid, forced exhalation. In healthy individuals, it is 8-11% less than the VC, mainly due to an increase in resistance to air flow in the small bronchi. In a number of diseases accompanied by an increase in resistance in the small bronchi, for example, in broncho-obstructive syndromes, pulmonary emphysema, EFVC changes.

IFZHEL

Inspiratory forced vital capacity (IFVC) is determined with the most rapid forced inspiration. It does not change with emphysema, but decreases with impaired patency respiratory tract.

Pneumotachometry

Pneumotachometry

Pneumotachometry evaluates the change in "peak" airflow velocities during forced inhalation and exhalation. It allows you to assess the state of bronchial patency. ###Pneumatic tachography

Pneumotachography is carried out using a pneumotachograph, which records the movement of the air stream.

Tests for the detection of overt or latent respiratory failure

Based on the determination of oxygen consumption and oxygen deficiency using spirography and ergospirography. This method can determine the oxygen consumption and oxygen deficiency in a patient when he performs a certain physical activity and at rest.

One of the main characteristics of external respiration is the minute volume of respiration (MOD). Lung ventilation is determined by the volume of air inhaled or exhaled per unit of time. MOD is the product of tidal volume times respiratory rate.. Normally, at rest, DO is 500 ml, the frequency of respiratory cycles is 12 - 16 per minute, hence the MOD is 6 - 7 l / min. Maximum ventilation of the lungs is the volume of air that passes through the lungs in 1 minute during the maximum frequency and depth of respiratory movements.

Alveolar ventilation

So, external respiration, or ventilation of the lungs, ensures that approximately 500 ml of air enters the lungs during each breath (DO). The saturation of the blood with oxygen and the removal of carbon dioxide occurs when contact of the blood of the pulmonary capillaries with the air contained in the alveoli. Alveolar air is the internal gas environment of the body of mammals and humans. Its parameters - the content of oxygen and carbon dioxide - are constant. The amount of alveolar air approximately corresponds to the functional residual capacity of the lungs - the amount of air that remains in the lungs after a quiet exhalation, and is normally 2500 ml. It is this alveolar air that is renewed by atmospheric air entering through the respiratory tract. It should be borne in mind that not all of the inhaled air is involved in pulmonary gas exchange, but only that part of it that reaches the alveoli. Therefore, to assess the effectiveness of pulmonary gas exchange, it is important not so much pulmonary ventilation as alveolar ventilation.

As you know, part of the tidal volume does not participate in gas exchange, filling the anatomically dead space of the respiratory tract - approximately 140 - 150 ml.

In addition, there are alveoli that are currently ventilated, but not supplied with blood. This part of the alveoli is the alveolar dead space. The sum of anatomical and alveolar dead spaces is called functional or physiological dead space. Approximately 1/3 of the respiratory volume falls on the ventilation of the dead space filled with air, which is not directly involved in gas exchange and only moves in the lumen of the airways during inhalation and exhalation. Therefore, ventilation of the alveolar spaces - alveolar ventilation - is pulmonary ventilation minus dead space ventilation. Normally, alveolar ventilation is 70 - 75% of the MOD value.

Calculation of alveolar ventilation is carried out according to the formula: MAV = (DO - MP)  BH, where MAV is minute alveolar ventilation, DO is tidal volume, MP is dead space volume, BH is respiratory rate.

Figure 6. Relationship between MOD and alveolar ventilation

We use these data to calculate another value characterizing alveolar ventilation - alveolar ventilation coefficient . This coefficient shows how much of the alveolar air is renewed with each breath. In the alveoli at the end of a quiet exhalation there is about 2500 ml of air (FFU), during inspiration 350 ml of air enters the alveoli, therefore, only 1/7 of the alveolar air is renewed (2500/350 = 7/1).

Breathing rate - the number of inhalations and exhalations per unit of time. An adult makes an average of 15-17 respiratory movements per minute. Great importance has a workout. In trained people, respiratory movements are performed more slowly and amount to 6-8 breaths per minute. So, in newborns, BH depends on a number of factors. When standing, the respiratory rate is greater than when sitting or lying down. During sleep, breathing is rarer (approximately 1/5).

During muscular work, breathing quickens by 2-3 times, reaching up to 40-45 cycles per minute or more in some types of sports exercises. Temperature affects breathing rate environment, emotions, mental work.

Depth of breathing or tidal volume - the amount of air that a person inhales and exhales during normal breathing. During each respiratory movement, 300-800 ml of air in the lungs is exchanged. Tidal volume (TO) falls as the respiratory rate increases.

Minute breathing volume- the amount of air that passes through the lungs per minute. It is determined by the product of the amount of inhaled air by the number of respiratory movements in 1 min: MOD = TO x BH.

In an adult, the MOD is 5-6 liters. Age changes indicators of external respiration are presented in table. 27.

Tab. 27. Indicators of external respiration (according to: Khripkova, 1990)

The breathing of a newborn baby is frequent and shallow and is subject to significant fluctuations. With age, there is a decrease in respiratory rate, an increase in tidal volume and pulmonary ventilation. Due to the higher respiratory rate in children, the minute volume of breathing (in terms of 1 kg of weight) is much higher than in adults.

Ventilation of the lungs may vary depending on the behavior of the child. In the first months of life, anxiety, crying, screaming increase ventilation by 2-3 times, mainly due to an increase in the depth of breathing.

Muscular work increases the minute volume of breathing in proportion to the magnitude of the load. The older the children, the more intense muscular work they can perform and the more their ventilation increases. However, under the influence of training, the same work can be performed with a smaller increase in lung ventilation. At the same time, trained children are able to increase their minute breathing volume during work to a higher level than their peers who do not exercise. exercise(quoted from: Markosyan, 1969). With age, the effect of training is more pronounced, and in adolescents 14-15 years old, training causes the same significant shifts in pulmonary ventilation as in adults.

Vital capacity of the lungs- the maximum amount of air that can be exhaled after a maximum inspiration. Vital capacity (VC) is an important functional characteristic of respiration and consists of tidal volume, inspiratory reserve volume and expiratory reserve volume.

At rest, the tidal volume is small compared to the total volume of air in the lungs. Therefore, a person can both inhale and exhale a large additional volume. Inspiratory reserve volume(RO vd) - the amount of air that a person can additionally inhale after a normal breath and is 1500-2000 ml. expiratory reserve volume(RO vyd) - the amount of air that a person can additionally exhale after a calm exhalation; its value is 1000-1500 ml.

Even after the deepest expiration, some air remains in the alveoli and airways of the lungs - this is residual volume(OO). However, during quiet breathing, significantly more air remains in the lungs than the residual volume. The amount of air remaining in the lungs after a quiet expiration is called functional residual capacity(FOE). It consists of residual lung volume and expiratory reserve volume.

The largest number The amount of air that completely fills the lungs is called the total lung capacity (TLC). It includes the residual volume of air and vital capacity of the lungs. The ratio between the volumes and capacities of the lungs is shown in fig. 8 (Atl., p. 169). Vital capacity changes with age (Table 28). Since the measurement of lung capacity requires the active and conscious participation of the child himself, it is measured in children from 4-5 years old.

By the age of 16-17, the vital capacity of the lungs reaches values ​​characteristic of an adult. The vital capacity of the lungs is an important indicator of physical development.

Tab. 28. The average value of the vital capacity of the lungs, ml (according to: Khripkova, 1990)

FROM childhood and up to 18-19 years, the vital capacity of the lungs increases, from 18 to 35 years it remains at a constant level, and after 40 it decreases. This is due to a decrease in the elasticity of the lungs and the mobility of the chest.

The vital capacity of the lungs depends on a number of factors, in particular on body length, weight and sex. To assess the vital capacity, the proper value is calculated using special formulas:

for men:

WELCOME should = [(growth, cm∙ 0.052)] - [(age, years ∙ 0,022)] - 3,60;

for women:

WELCOME should = [(growth, cm∙ 0.041)] - [(age, years ∙ 0,018)] - 2,68;

for boys 8-10 years old:

WELCOME should = [(growth, cm∙ 0.052)] - [(age, years ∙ 0,022)] - 4,6;

for boys 13-16 years old:

WELCOME should = [(growth, cm∙ 0.052)] - [(age, years ∙ 0,022)] - 4,2

for girls 8-16 years old:

WELCOME should = [(growth, cm∙ 0.041)] - [(age, years ∙ 0,018)] - 3,7

In women, VC is 25% less than in men; in trained people it is greater than in untrained people. It is especially high when practicing such sports as swimming, running, skiing, rowing, etc. For example, for rowers it is 5,500 ml, for swimmers - 4,900 ml, for gymnasts - 4,300 ml, for football players - 4 200 ml, weightlifters - about 4,000 ml. To determine the vital capacity of the lungs, a spirometer device (spirometry method) is used. It consists of a vessel with water and another vessel placed upside down with a capacity of at least 6 liters, which contains air. A system of tubes is connected to the bottom of this second vessel. Through these tubes, the subject breathes, so that the air in his lungs and in the vessel forms a single system.

Gas exchange

The content of gases in the alveoli. During the act of inhalation and exhalation, a person constantly ventilates the lungs, maintaining the gas composition in the alveoli. A person inhales atmospheric air with a high content of oxygen (20.9%) and a low content of carbon dioxide (0.03%). Exhaled air contains 16.3% oxygen and 4% carbon dioxide. When inhaling, out of 450 ml of inhaled atmospheric air, only about 300 ml enters the lungs, and approximately 150 ml remains in the airways and does not participate in gas exchange. During the exhalation, which follows the inhalation, this air is brought out unchanged, that is, it does not differ in its composition from the atmospheric one. That's why they call it air. dead or harmful space. The air that has reached the lungs is mixed here with the 3000 ml of air already in the alveoli. The gas mixture in the alveoli involved in gas exchange is called alveolar air. The incoming portion of air is small compared to the volume to which it is added, so the complete renewal of all the air in the lungs is a slow and intermittent process. The exchange between atmospheric and alveolar air has little effect on the alveolar air, and its composition remains practically constant, as can be seen from Table. 29.

Tab. 29. Composition of inhaled, alveolar and exhaled air, in %

When comparing the composition of the alveolar air with the composition of the inhaled and exhaled air, it can be seen that the body retains one fifth of the incoming oxygen for its needs, while the amount of CO 2 in the exhaled air is 100 times greater than the amount that enters the body during inhalation. Compared to inhaled air, it contains less oxygen, but more CO 2 . The alveolar air comes into close contact with the blood, and the gas composition depends on its composition. arterial blood.

Children have a different composition of both exhaled and alveolar air: the younger the children, the lower their percentage of carbon dioxide and the greater the percentage of oxygen in exhaled and alveolar air, respectively, the lower the percentage of oxygen use (Table 30). Consequently, in children, the efficiency of pulmonary ventilation is low. Therefore, for the same amount of oxygen consumed and carbon dioxide released, a child needs to ventilate the lungs more than adults.

Tab. 30. Composition of exhaled and alveolar air
(average data for: Shalkov, 1957; comp. on: Markosyan, 1969)

Since in young children breathing is frequent and shallow, a large proportion of the respiratory volume is the volume of "dead" space. As a result, the exhaled air consists more of atmospheric air, and it has a lower percentage of carbon dioxide and a percentage of oxygen utilization from a given volume of breathing. As a result, the efficiency of ventilation in children is low. Despite the increased, compared with adults, the percentage of oxygen in the alveolar air in children is not significant, since 14-15% of oxygen in the alveoli is sufficient to completely saturate blood hemoglobin. More oxygen than is bound by hemoglobin cannot pass into the arterial blood. Low level The content of carbon dioxide in the alveolar air in children indicates its lower content in the arterial blood compared to adults.

Gas exchange in the lungs. Gas exchange in the lungs is carried out as a result of the diffusion of oxygen from the alveolar air into the blood and carbon dioxide from the blood into the alveolar air. Diffusion occurs due to the difference in the partial pressure of these gases in the alveolar air and their saturation in the blood.

Partial pressure- this is the part of the total pressure that falls on the proportion of this gas in the gas mixture. The partial pressure of oxygen in the alveoli (100 mm Hg) is much higher than the tension of O 2 in the venous blood entering the capillaries of the lungs (40 mm Hg). The partial pressure parameters for CO 2 have the opposite value - 46 mm Hg. Art. at the beginning of the pulmonary capillaries and 40 mm Hg. Art. in the alveoli. The partial pressure and tension of oxygen and carbon dioxide in the lungs are given in Table. 31.

Tab. 31. Partial pressure and tension of oxygen and carbon dioxide in the lungs, mm Hg. Art.

These pressure gradients (differences) are the driving force for O 2 and CO 2 diffusion, i.e. gas exchange in the lungs.

The diffusion capacity of the lungs for oxygen is very high. This is due to the large number of alveoli (hundreds of millions), their large gas exchange surface (about 100 m 2), as well as the small thickness (about 1 micron) of the alveolar membrane. The diffusion capacity of the lungs for oxygen in humans is about 25 ml / min per 1 mm Hg. Art. For carbon dioxide, due to its high solubility in the lung membrane, the diffusion capacity is 24 times higher.

Oxygen diffusion is provided by a partial pressure difference of about 60 mm Hg. Art., and carbon dioxide - only about 6 mm Hg. Art. The time for blood to flow through the capillaries of the small circle (about 0.8 s) is enough to completely equalize the partial pressure and gas tension: oxygen dissolves in the blood, and carbon dioxide passes into the alveolar air. The transition of carbon dioxide into alveolar air at a relatively small pressure difference is explained by the high diffusion capacity for this gas (Atl., Fig. 7, p. 168).

Thus, in the pulmonary capillaries there is a constant exchange of oxygen and carbon dioxide. As a result of this exchange, the blood is saturated with oxygen and released from carbon dioxide.

The main methods for studying breathing in humans include:

· Spirometry is a method for determining the vital capacity of the lungs (VC) and its constituent air volumes.

· Spirography - a method of graphic registration of indicators of the function of the external link of the respiratory system.

· Pneumotachometry - a method of measuring the maximum rate of inhalation and exhalation during forced breathing.

Pneumography is a method of recording the respiratory movements of the chest.

· Peak fluorometry - a simple way of self-assessment and continuous monitoring of bronchial patency. The device - peak flowmeter allows you to measure the volume of air passing during exhalation per unit time (peak expiratory flow).

· Functional trials(Shtange and Genche).

Spirometry

The functional state of the lungs depends on age, sex, physical development and a number of other factors. The most common characteristic of the state of the lungs is the measurement of lung volumes, which indicate the development of the respiratory organs and the functional reserves of the respiratory system. The volume of air inhaled and exhaled can be measured using a spirometer.

Spirometry is the most important way to assess the function of external respiration. This method determines the vital capacity of the lungs, lung volumes, as well as the volumetric airflow rate. During spirometry, a person inhales and exhales with maximum force. The most important data is given by the analysis of the expiratory maneuver - exhalation. Lung volumes and capacities are called static (basic) respiratory parameters. There are 4 primary lung volumes and 4 containers.

Vital capacity of the lungs

Vital capacity is the maximum amount of air that can be exhaled after a maximum inhalation. During the study, the actual VC is determined, which is compared with the due VC (JEL) and calculated by the formula (1). In an adult of average height, JEL is 3-5 liters. In men, its value is about 15% more than in women. Schoolchildren aged 11-12 have a JEL of about 2 liters; children under 4 years old - 1 liter; newborns - 150 ml.

VC=DO+ROVD+ROvyd, (1)

Where VC is the vital capacity of the lungs; DO - respiratory volume; Rvd - inspiratory reserve volume; ROvyd - expiratory reserve volume.

JEL (l) \u003d 2.5Chrost (m). (2)

Tidal volume

Tidal volume (TO), or the depth of breathing, is the volume of inhaled and

air exhaled at rest. In adults, DO = 400-500 ml, in children 11-12 years old - about 200 ml, in newborns - 20-30 ml.

expiratory reserve volume

Expiratory reserve volume (ERV) is the maximum volume that can be forcefully exhaled after a quiet exhalation. ROvy = 800-1500 ml.

Inspiratory reserve volume

Inspiratory reserve volume (IRV) is the maximum amount of air that can be additionally inhaled after a normal inspiration. Inspiratory reserve volume can be determined in two ways: calculated or measured with a spirometer. To calculate, it is necessary to subtract the sum of the respiratory and expiratory reserve volumes from the VC value. To determine the inspiratory reserve volume using a spirometer, it is necessary to draw from 4 to 6 liters of air into the spirometer and, after a calm breath from the atmosphere, take a maximum breath from the spirometer. The difference between the initial volume of air in the spirometer and the volume remaining in the spirometer after a deep breath corresponds to the inspiratory reserve volume. Rovd \u003d 1500-2000 ml.

Residual volume

Residual volume (VR) is the volume of air remaining in the lungs even after maximum exhalation. It is measured only by indirect methods. The principle of one of them is that a foreign gas such as helium is injected into the lungs (dilution method) and the volume of the lungs is calculated from the change in its concentration. The residual volume is 25-30% of the VC value. Take OO=500-1000 ml.

Total lung capacity

Total capacity lung (TEL) - the amount of air in the lungs after a maximum breath. TEL = 4500-7000 ml. Calculated by formula (3)

HEL \u003d WILD + OO. (3)

Functional residual lung capacity

Functional residual capacity (FRC) is the amount of air remaining in the lungs after a normal exhalation.

Calculated by formula (4)

FOEL = Rovd. (four)

Input capacity

Inlet capacity (ERC) is the maximum volume of air that can be inhaled after a normal exhalation. Calculated by formula (5)

EVD=DO+ROVD. (5)

In addition to static indicators characterizing the degree of physical development of the respiratory apparatus, there are additional - dynamic indicators that provide information on the effectiveness of lung ventilation and the functional state of the respiratory tract.

forced vital capacity

Forced vital capacity (FVC) is the amount of air that can be exhaled during a forced exhalation after a maximum inhalation. Normally, the difference between VC and FVC is 100-300 ml. An increase in this difference to 1500 ml or more indicates resistance to air flow due to narrowing of the lumen of the small bronchi. FVC = 3000-7000 ml.

Anatomical dead space

Anatomical dead space (DMP) - the volume in which gas exchange does not occur (nasopharynx, trachea, large bronchi) - cannot be directly determined. DMP = 150 ml.

Breathing rate

Respiratory rate (RR) - the number of respiratory cycles in one minute. BH \u003d 16-18 d.c. / min.

Minute breathing volume

Minute respiratory volume (MOD) - the amount of air ventilated in the lungs in 1 minute.

MOD = TO + BH. MOD = 8-12 l.

Alveolar ventilation

Alveolar ventilation (AV) - the volume of exhaled air entering the alveoli. AB = 66 - 80% of MOD. AB = 0.8 l/min.

Breath reserve

Respiratory reserve (RD) - an indicator that characterizes the possibility of increasing ventilation. Normally, RD is 85% of the maximum ventilation of the lungs (MVL). MVL = 70-100 l / min.