What is the minute volume of breathing at rest. External respiration and lung volumes

Lung volumes and capacities

In the process of pulmonary ventilation, the gas composition of the alveolar air is continuously updated. The amount of pulmonary ventilation is determined by the depth of breathing, or tidal volume, and the frequency of respiratory movements. During respiratory movements, the lungs of a person are filled with inhaled air, the volume of which is part of the total volume of the lungs. To quantify lung ventilation, total lung capacity was divided into several components or volumes. In this case, the lung capacity is the sum of two or more volumes.

Lung volumes are divided into static and dynamic. Static lung volumes are measured with completed respiratory movements without limiting their speed. Dynamic lung volumes are measured during respiratory movements with a time limit for their implementation.

lung volumes. The volume of air in the lungs and respiratory tract depends on the following indicators: 1) anthropometric individual characteristics of a person and the respiratory system; 2) properties of lung tissue; 3) surface tension of the alveoli; 4) the force developed by the respiratory muscles.

Tidal volume (TO) The volume of air that a person inhales and exhales during quiet breathing. In an adult, DO is approximately 500 ml. The value of TO depends on the measurement conditions (rest, load, body position). DO is calculated as the average value after measuring approximately six quiet respiratory movements.

Inspiratory reserve volume (RIV)- the maximum volume of air that the subject can inhale after a quiet breath. The value of ROVD is 1.5-1.8 liters.

Expiratory reserve volume (ERV) is the maximum amount of air that a person can additionally exhale from the level of calm exhalation. The value of ROvyd is lower in the horizontal position than in the vertical position, and decreases with obesity. It is equal to an average of 1.0-1.4 liters.

Residual volume (RO) is the volume of air that remains in the lungs after maximum exhalation. The value of the residual volume is 1.0-1.5 liters.

The study of dynamic lung volumes is of scientific and clinical interest and their description is beyond the scope of the course of normal physiology.

Lung containers. Vital capacity (VC) includes tidal volume, inspiratory reserve volume, and expiratory reserve volume. In middle-aged men, VC varies within 3.5-5.0 liters or more. For women, lower values ​​are typical (3.0-4.0 l). Depending on the method of measuring VC, the VC of inhalation is distinguished, when the deepest breath is taken after a full exhalation and the VC of exhalation, when the maximum exhalation is made after a full breath.

The inspiratory capacity (Evd) is equal to the sum of the tidal volume and the inspiratory reserve volume. In humans, EUD averages 2.0-2.3 liters.

Functional residual capacity (FRC) - the volume of air in the lungs after a quiet exhalation. FRC is the sum of expiratory reserve volume and residual volume. FRC is measured by the methods of gas dilution, or dilution of gases, and plethysmographically. The FRC value is significantly affected by the level of physical activity of a person and the position of the body: FRC is less in a horizontal position of the body than in a sitting or standing position. FRC decreases with obesity due to a decrease in the overall compliance of the chest.

Total lung capacity (TLC) is the volume of air in the lungs at the end of a full breath. OEL is calculated in two ways: OEL - OO + VC or OEL - FOE + Evd. TRL can be measured using plethysmography or gas dilution.

Measurement of lung volumes and capacities is of clinical importance in the study of lung function in healthy individuals and in the diagnosis of human lung disease. The measurement of lung volumes and capacities is usually performed by spirometry, pneumotachometry with the integration of indicators and body plethysmography. Static lung volumes may decrease in pathological conditions leading to limited expansion of the lungs. These include neuromuscular diseases, diseases of the chest, abdomen, pleural lesions that increase the rigidity of the lung tissue, and diseases that cause a decrease in the number of functioning alveoli (atelectasis, resection, cicatricial changes in the lungs).

For comparability of the results of measurements of gas volumes and capacities, the obtained data should be correlated with conditions in the lungs, where the temperature of the alveolar air corresponds to body temperature, the air is at a certain pressure and is saturated with water vapor. This state is called the standard state and is denoted by the letters BTPS (body temperature, pressure, saturated).

To assess the quality of lung function, he examines respiratory volumes (using special devices - spirometers).

Tidal volume (TO) is the amount of air that a person inhales and exhales during quiet breathing in one cycle. Normal = 400-500 ml.

Minute respiratory volume (MOD) - the volume of air passing through the lungs in 1 minute (MOD = TO x NPV). Normal = 8-9 liters per minute; about 500 liters per hour; 12000-13000 liters per day. With an increase in physical activity, the MOD increases.

Not all inhaled air is involved in the ventilation of the alveoli (gas exchange), because. some of it does not reach the acini and remains in the airways, where there is no possibility for diffusion. The volume of such airways is called "respiratory dead space". Normal in an adult = 140-150 ml, i.e. 1/3 TO.

Inspiratory reserve volume (IRV) is the amount of air that a person can inhale during the strongest maximum breath after a quiet breath, i.e. over to. Normal = 1500-3000 ml.

Expiratory reserve volume (ERV) is the amount of air that a person can additionally exhale after a normal exhalation. Normal = 700-1000 ml.

Vital capacity of the lungs (VC) - the amount of air that a person can exhale as much as possible after the deepest breath (VC=DO+ROVd+ROVd = 3500-4500 ml).

Residual lung volume (RLV) is the amount of air remaining in the lungs after maximum exhalation. Normal = 100-1500 ml.

Total lung capacity (TLC) is the maximum amount of air that can be in the lungs. TEL = VC + TOL = 4500-6000 ml.

DIFFUSION OF GAS

The composition of the inhaled air: oxygen - 21%, carbon dioxide - 0.03%.

The composition of the exhaled air: oxygen-17%, carbon dioxide - 4%.

The composition of the air contained in the alveoli: oxygen-14%, carbon dioxide -5.6% o.

As you exhale, the alveolar air mixes with the air in the airways (in the "dead space"), which causes the indicated difference in air composition.

The transition of gases through the air-blood barrier is due to the difference in concentrations on both sides of the membrane.

Partial pressure is that part of the pressure that falls on a given gas. At atmospheric pressure of 760 mm Hg, the partial pressure of oxygen is 160 mm Hg. (i.e. 21% of 760), in the alveolar air, the partial pressure of oxygen is 100 mm Hg, and carbon dioxide is 40 mm Hg.

The gas pressure is the partial pressure in the liquid. Oxygen tension in venous blood - 40 mm Hg. Due to the pressure gradient between the alveolar air and blood - 60 mm Hg. (100 mm Hg and 40 mm Hg) oxygen diffuses into the blood, where it binds to hemoglobin, turning it into oxyhemoglobin. Blood containing a large amount of oxyhemoglobin is called arterial. 100 ml of arterial blood contains 20 ml of oxygen, 100 ml of venous blood contains 13-15 ml of oxygen. Also, along the pressure gradient, carbon dioxide enters the blood (because it is contained in large quantities in tissues) and carbhemoglobin is formed. In addition, carbon dioxide reacts with water, forming carbonic acid (the reaction catalyst is the carbonic anhydrase enzyme found in erythrocytes), which decomposes into a hydrogen proton and a bicarbonate ion. CO 2 tension in venous blood - 46 mm Hg; in the alveolar air - 40 mm Hg. (pressure gradient = 6 mmHg). Diffusion of CO 2 occurs from the blood into the external environment.

IVL! If you understand it, it is equivalent to the appearance, as in films, of a superhero (doctor) super weapons(if the doctor understands the subtleties of mechanical ventilation) against the death of the patient.

To understand mechanical ventilation, you need basic knowledge: physiology = pathophysiology (obstruction or restriction) of breathing; the main parts, the structure of the ventilator; provision of gases (oxygen, atmospheric air, compressed gas) and dosing of gases; adsorbers; elimination of gases; breathing valves; breathing hoses; breathing bag; humidification system; breathing circuit (semi-closed, closed, semi-open, open), etc.

All ventilators carry out ventilation by volume or by pressure (whatever they are called, depending on which mode the doctor has set). Basically, the doctor sets the ventilation mode for obstructive pulmonary diseases (or during anesthesia) by volume, with restriction by pressure.

The main types of IVL are designated as follows:

CMV (Continuous mandatory ventilation) - Controlled (artificial) ventilation of the lungs

VCV (Volume controlled ventilation)

PCV (Pressure controlled ventilation)

IPPV (Intermittent positive pressure ventilation) - ventilation with intermittent positive pressure on inspiration

ZEEP (Zero endexpiratory pressure) - mechanical ventilation with end-expiratory pressure equal to atmospheric

PEEP (Positive endexpiratory pressure) - Positive end-expiratory pressure (PEEP)

CPPV (Continuous positive pressure ventilation) - mechanical ventilation with PEEP

IRV (Inversed ventilation ratio)

SIMV (Synchronized intermittent mandatory ventilation) - Synchronized intermittent mandatory ventilation = A combination of spontaneous and hardware breathing, when, when the frequency of spontaneous breathing decreases to a certain value, with continued attempts to inhale, overcoming the level of the set trigger, hardware breathing is synchronously connected

You should always look at the letters ..P.. or ..V.. If P (Pressure) means by pressure, if V (Volume) by volume.

1. Vt is the tidal volume,
2. f - respiratory rate, MV - minute ventilation
3. PEEP - PEEP = positive end expiratory pressure
4. Tinsp - inspiratory time;
5. Pmax is the inspiratory pressure or maximum airway pressure.
6. Gas flow of oxygen and air.

1. Tidal volume(Vt, TO) set from 5 ml to 10 ml / kg (depending on the pathology, normally 7-8 ml per kg) = how much volume the patient should inhale at a time. But for this you need to find out the ideal (proper, predicted) body weight of a given patient using the formula (NB! remember):

Men: BMI (kg) = 50 + 0.91 (height, cm - 152.4)

Women: BMI (kg) = 45.5 + 0.91 (height, cm - 152.4).

Example: a man weighs 150 kg. This does not mean that we have to set the tidal volume to 150kg 10ml= 1500 ml. First, we calculate BMI = 50 + 0.91 (165cm-152.4) = 50 + 0.91 12.6 = 50 + 11.466 = 61,466 kg should weigh our patient. Imagine, oh allai deseishi! For a man with a weight of 150 kg and a height of 165 cm, we should set the tidal volume (TR) from 5 ml/kg (61.466 5=307.33 ml) to 10 ml/kg (61.466 10=614.66 ml) depending on pathology and distensibility of the lungs.

2. The second parameter that the doctor must set is breathing rate(f). The normal respiratory rate is 12 to 18 per minute at rest. And we don't know what frequency to set 12 or 15, 18 or 13? To do this, we must calculate due MOD (MV). Synonyms for minute respiratory volume (MOD) = minute ventilation of the lungs (MVL), maybe something else ... This means how much air the patient needs (ml, l) per minute.

MOD=BMI kg:10+1

according to the Darbinyan formula (an outdated formula, often leads to hyperventilation).

Or a modern calculation: MOD \u003d BMIkg 100.

(100%, or 120%-150% depending on the patient's body temperature.., from the basal metabolism in short).

Example: The patient is a woman, weighs 82 kg, height is 176 cm. BMI=45.5+0.91 (height, cm – 152.4)=45.5+0.91 (176 cm-152.4)= 45.5+0.91 23.6=45.5+21.476= 66,976 kg should weigh. MOD=67(immediately rounded) 100= 6700 ml or 6,7 liters per minute. Now only after these calculations we can find out the respiratory rate. f=MOD:TO=6700 ml: 536 ml=12.5 times per minute, so 12 or 13 once.

3. Install PEER. Normal (before) 3-5 mbar. Now you can 8-10 mbar in patients with normal lungs.

4. The inspiratory time in seconds is set by the ratio of inhalation to exhalation: I: E=1:1,5-2 . In this parameter, knowledge about the respiratory cycle, ventilation-perfusion ratio, etc. will be useful.

5. Pmax, Pinsp peak pressure is set so as not to cause barotrauma or tear the lungs. Normally I think 16-25 mbar, depending on the elasticity of the lungs, the weight of the patient, the extensibility of the chest, etc. In my knowledge, the lungs can rupture when Pinsp is more than 35-45 mbar.

6. The fraction of inhaled oxygen (FiO 2) should not exceed 55% in the inhaled respiratory mixture.

All calculations and knowledge are needed in order for the patient to have such indicators: PaO 2 \u003d 80-100 mm Hg; PaCO 2 \u003d 35-40 mm Hg. Just, oh allai deseishi!

Breathing rate - the number of inhalations and exhalations per unit of time. An adult makes an average of 15-17 respiratory movements per minute. Training is of great importance. 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. The respiratory rate is affected by the ambient temperature, 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-related changes in external respiration parameters 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 respiratory minute volume during work to a higher level than their non-exercising peers (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 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 to 18-19 years of age, 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 gender. 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 doing sports such 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 own 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 of the arterial blood depends on its composition.

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. The low level 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.