Breathing volumes. Pulmonary volumes and lung capacities Magnitude of minute volume of respiration

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Common to all living cells is the process of breaking down organic molecules through a successive series of enzymatic reactions, resulting in the release of energy. Almost any process in which the oxidation of organic substances leads to the release of chemical energy is called breathing. If it requires oxygen, then breathing is calledaerobic, and if reactions occur in the absence of oxygen - anaerobic breathing. For all tissues of vertebrate animals and humans, the main source of energy is the processes of aerobic oxidation, which occur in the mitochondria of cells adapted to convert the energy of oxidation into the energy of reserve high-energy compounds such as ATP. The sequence of reactions by which the cells of the human body use the energy of the bonds of organic molecules is called internal, tissue or cellular breathing.

The respiration of higher animals and humans is understood as a set of processes that ensure the supply of oxygen to the internal environment of the body, its use for the oxidation of organic substances and the removal of carbon dioxide from the body.

The function of breathing in humans is realized by:

1) external, or pulmonary, respiration, which carries out gas exchange between the external and internal environment of the body (between air and blood);
2) blood circulation, which ensures the transport of gases to and from tissues;
3) blood as a specific gas transport medium;
4) internal, or tissue, respiration, which carries out the direct process of cellular oxidation;
5) means of neurohumoral regulation of breathing.

The result of the activity of the external respiration system is the enrichment of the blood with oxygen and the release of excess carbon dioxide.

Changes in the gas composition of blood in the lungs are ensured by three processes:

1) continuous ventilation of the alveoli to maintain the normal gas composition of the alveolar air;
2) diffusion of gases through the alveolar-capillary membrane in a volume sufficient to achieve equilibrium in the pressure of oxygen and carbon dioxide in the alveolar air and blood;
3) continuous blood flow in the capillaries of the lungs in accordance with the volume of their ventilation

Lung capacity

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Total capacity. The amount of air in the lungs after maximum inspiration is the total lung capacity, the value of which in an adult is 4100-6000 ml (Fig. 8.1).
It consists of the vital capacity of the lungs, which is the amount of air (3000-4800 ml) that comes out of the lungs during the deepest exhalation after the deepest inhalation, and
residual air (1100-1200 ml), which still remains in the lungs after maximum exhalation.

Total capacity = Vital capacity + Residual volume

Vital capacity makes up three lung volumes:

1) tidal volume , representing the volume (400-500 ml) of air inhaled and exhaled during each respiratory cycle;
2) reserve volumeinhalation (additional air), i.e. the volume (1900-3300 ml) of air that can be inhaled during a maximum inhalation after a normal inhalation;
3) expiratory reserve volume (reserve air), i.e. volume (700-1000 ml) that can be exhaled at maximum exhalation after normal exhalation.

Vital capacity = Inspiratory reserve volume + Tidal volume + Expiratory reserve volume

functional residual capacity. During quiet breathing, after exhalation, an expiratory reserve volume and residual volume remain in the lungs. The sum of these volumes is called functional residual capacity, as well as normal lung capacity, resting capacity, equilibrium capacity, buffer air.

functional residual capacity = Expiratory reserve volume + Residual volume

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

To understand mechanical ventilation you need basic knowledge: physiology = pathophysiology (obstruction or restriction) of breathing; main parts, 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 provide ventilation by volume or pressure (no matter what they are called; depending on what mode the doctor has set). Basically, the doctor sets the mechanical ventilation mode for obstructive pulmonary diseases (or during anesthesia) by volume, during restriction by pressure.

The main types of ventilation are designated as follows:

CMV (Continuous mandatory ventilation) - Controlled (artificial) ventilation

VCV (Volume controlled ventilation) - volume controlled ventilation

PCV (Pressure controlled ventilation) - pressure controlled ventilation

IPPV (Intermittent positive pressure ventilation) - mechanical ventilation with intermittent positive pressure during inspiration

ZEEP (Zero endexpiratory pressure) - ventilation with pressure at the end of expiration equal to atmospheric

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

CPPV (Continuous positive pressure ventilation) - ventilation with PDKV

IRV (Inversed ratio ventilation) - mechanical ventilation with a reverse (inverted) inhalation:exhalation ratio (from 2:1 to 4:1)

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

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

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

1. Tidal volume(Vt, DO) set from 5 ml to 10 ml/kg (depending on the pathology, normal 7-8 ml per kg) = how much volume the patient should inhale at a time. But to do 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 should 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 our patient should weigh. Imagine, oh allai deseishi! For a man with a weight of 150 kg and a height of 165 cm, we must set the tidal volume (TI) from 5 ml/kg (61.466·5=307.33 ml) to 10 ml/kg (61.466·10=614.66 ml) depending on pathology and extensibility 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 breathing volume (MVR) = minute ventilation (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 (outdated formula, often leads to hyperventilation).

Or modern calculation: MOD=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 (rounded up immediately) 100 = 6700 ml or 6,7 liters per minute. Now only after these calculations can we find out the breathing frequency. f=MOD:UP TO=6700 ml: 536 ml=12.5 times per minute, which means 12 or 13 once.

3. Install REER. Normally (previously) 3-5 mbar. Now you can 8-10 mbar in patients with normal lungs.

4. The inhalation time in seconds is determined 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 rupture 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, lungs can rupture when Pinsp is more than 35-45 mbar.

6. The fraction of inhaled oxygen (FiO 2) should be no more than 55% in the inhaled respiratory mixture.

All calculations and knowledge are needed so that the patient has the following indicators: PaO 2 = 80-100 mm Hg; PaCO 2 =35-40 mm Hg. Just, oh allai deseishi!

Tidal volume (TV) 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).

Of this, about 150 ml is the volume of air in the functional dead space (FSD) in the larynx, trachea, and bronchi, which does not take part in gas exchange. The functional role of HFMP is that it mixes with the inhaled air, moisturizing and warming it.

Expiratory reserve volume

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

Inspiratory reserve volume

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

Vital capacity of the lungs

Vital capacity of the lungs (VC) is the maximum amount of air exhaled after the deepest inhalation. Vital vital capacity is one of the main indicators of the condition of the external respiration apparatus, widely used in medicine. Together with the residual volume, i.e. the volume of air remaining in the lungs after the deepest exhalation, vital capacity forms the total lung capacity (TLC).

Normally, vital capacity is about 3/4 of the total lung capacity and characterizes the maximum volume within which a person can change the depth of his breathing. During quiet breathing, a healthy adult uses a small part of vital capacity: inhales and exhales 300-500 ml of air (the so-called tidal volume). In this case, the inspiratory reserve volume, i.e. the amount of air that a person is able to additionally inhale after a quiet inhalation, and the reserve volume of exhalation, equal to the volume of additionally exhaled air after a quiet exhalation, averages approximately 1500 ml each. During physical activity, tidal volume increases due to the use of inhalation and exhalation reserves.

Vital capacity is an indicator of the mobility of the lungs and chest. Despite the name, it does not reflect breathing parameters in real (“life”) conditions, since even with the highest demands placed on the respiratory system by the body, the depth of breathing never reaches the maximum possible value.

From a practical point of view, it is inappropriate to establish a “single” standard for the vital capacity of the lungs, since this value depends on a number of factors, in particular on age, gender, body size and position, and the degree of fitness.

With age, the vital capacity of the lungs decreases (especially after 40 years). This is due to a decrease in the elasticity of the lungs and the mobility of the chest. Women have on average 25% less than men.

The relationship with height can be calculated using the following equation:

VC=2.5*height (m)

Vital capacity depends on the position of the body: in a vertical position it is slightly greater than in a horizontal position.

This is explained by the fact that in an upright position the lungs contain less blood. In trained people (especially swimmers and rowers), it can be up to 8 liters, since athletes have highly developed auxiliary respiratory muscles (pectoralis major and minor).

Residual volume

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

Total lung capacity

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

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

Vital capacity of the lungs. Systematic physical education and sports contribute to the development of respiratory muscles and expansion of the chest. Already 6-7 months after starting swimming or running, the vital capacity of young athletes’ lungs can increase by 500 cc. and more. A decrease in it is a sign of overwork.

The vital capacity of the lungs is measured with a special device - a spirometer. To do this, first close the hole in the inner cylinder of the spirometer with a stopper and disinfect its mouthpiece with alcohol. After taking a deep breath, exhale deeply through the mouthpiece. In this case, air should not pass past the mouthpiece or through the nose.

The measurement is repeated twice, and the highest result is recorded in the diary.

The vital capacity of the lungs in humans ranges from 2.5 to 5 liters, and in some athletes it reaches 5.5 liters or more. The vital capacity of the lungs depends on age, gender, physical development and other factors. A decrease of more than 300 cc may indicate overwork.

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

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

Minute respiration volume (MRV) is the volume of air passing through the lungs in 1 minute (MRV = DO x RR). Normal = 8-9 liters per minute; about 500 l per hour; 12000-13000 liters per day. With increasing physical activity, MOD increases.

Not all inhaled air participates in alveolar ventilation (gas exchange), because some of it does not reach the acini and remains in the respiratory tract, where there is no opportunity for diffusion. The volume of such airways is called “respiratory dead space”. Normally for 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 inhalation after a quiet inhalation, i.e. over DO. Normal = 1500-3000 ml.

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

Vital capacity of the lungs (VC) is the amount of air that a person can maximally exhale after the deepest inhalation (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 held in the lungs. TEL=VEL+TOL = 4500-6000 ml.

DIFFUSION OF GASES

Composition of inhaled air: oxygen - 21%, carbon dioxide - 0.03%.

Composition of exhaled air: oxygen - 17%, carbon dioxide - 4%.

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

As you exhale, the alveolar air is mixed with the air in the respiratory tract (in the “dead space”), which causes the indicated difference in air composition.

The transition of gases through the air-hematic 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 an 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.

Gas voltage is the partial pressure in a liquid. Oxygen tension in venous blood is 40 mm Hg. Due to the pressure gradient between alveolar air and blood - 60 mm Hg. (100 mm Hg and 40 mm Hg), oxygen diffuses into the blood, where it binds to hemoglobin, converting 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 (since it is contained in large quantities in the tissues) and carbhemoglobin is formed. In addition, carbon dioxide reacts with water, forming carbonic acid (the reaction catalyst is the enzyme carbonic anhydrase, found in red blood cells), which breaks down into a hydrogen proton and bicarbonate ion. CO 2 tension in venous blood is 46 mm Hg; in alveolar air – 40 mm Hg. (pressure gradient = 6 mmHg). Diffusion of CO 2 occurs from the blood into the external environment.

SPIROGRAPHY.

Measurement device and principles.

Target: study algorithms for measuring basic parameters

external respiration using spirographs

1. Spirography method.

2. Breathing phases.

3. Technique for performing spirography. Static indicators.

4. Spirogram: flow volume – time.

5. Spirogram: volumetric flow rate – flow volume.

6. Body plethysmography.

7. Principles of modeling the operation of a spirograph in MS-9.

Literature:

Medical devices. Development and Application. John G. Webster, John W. Clark Jr., Michael R. Newman, Walter H. Olson, et al. 652 pp., 2004, chapter 9.

2. Trifonov E.V. Human pneumaticpsychosomatologyRussian-English-Russian encyclopedia, 15th ed., 2012.

Spirography

Spirography- a method of graphically recording changes in lung volumes during natural respiratory movements and volitional forced respiratory maneuvers.

Spirography allows you to obtain a number of indicators that describe lung ventilation. First of all, these are static volumes and capacities that characterize the elastic properties of the lungs and chest wall, as well as dynamic indicators that determine the amount of air ventilated through the respiratory tract during inhalation and exhalation per unit time. Indicators are determined in the mode of quiet breathing, and some - during forced breathing maneuvers.

In technical performance, all spirographs are divided into open and closed type devices(Fig. 1). In open-type devices, the patient inhales atmospheric air through a valve box, and the exhaled air enters a Douglas bag or a Tiso spirometer (capacity 100-200 l), sometimes to a gas meter, which continuously determines its volume. The air collected in this way is analyzed: the values ​​of oxygen absorption and carbon dioxide release per unit of time are determined. Closed-type devices use the air from the bell of the device, circulating in a closed circuit without communication with the atmosphere. Exhaled carbon dioxide is absorbed by a special absorber.

A

b

Rice. 1. Schematic representation of the simplest open-type spirograph (a) and (b).

Indications for spirography:

1. Determination of the type and degree of pulmonary insufficiency.

2. Monitoring pulmonary ventilation indicators in order to determine the degree and speed of progression of the disease.

3. Evaluation of the effectiveness of course treatment of diseases with bronchial obstruction with short- and long-acting bronchodilators, anticholinergics), inhalation and membrane-stabilizing drugs.

4. Carrying out differential diagnosis between pulmonary and heart failure in combination with other research methods.

5. Identification of initial signs of ventilation failure in persons at risk of pulmonary diseases, or in persons working under the influence of harmful production factors.

6. Performance examination and military examination based on assessment of pulmonary ventilation function in combination with clinical indicators.

7. Conducting bronchodilation tests to identify the reversibility of bronchial obstruction, as well as provocative inhalation tests to identify bronchial hyperreactivity.

Contraindications to spirography:

1. severe general condition of the patient, which does not make it possible to conduct research;

2. progressive angina pectoris, myocardial infarction, acute cerebrovascular accident;

3. malignant arterial hypertension, hypertensive crisis;

4. toxicosis of pregnancy, second half of pregnancy;

5. stage III circulatory failure;

6. severe pulmonary insufficiency that does not allow breathing maneuvers.

Breathing phases.

Lung volume. Breathing rate. Depth of breathing. Pulmonary air volumes. Tidal volume. Reserve, residual volume. Lung capacity.

External respiration process is caused by changes in the volume of air in the lungs during the inhalation and exhalation phases of the respiratory cycle. During quiet breathing, the ratio of the duration of inhalation to exhalation in the respiratory cycle is on average 1:1.3. External breathing of a person is characterized by the frequency and depth of respiratory movements. Breathing rate a person is measured by the number of respiratory cycles within 1 minute and its value at rest in an adult varies from 12 to 20 per 1 minute. This indicator of external respiration increases with physical work, increasing ambient temperature, and also changes with age. For example, in newborns the respiratory rate is 60-70 per 1 min, and in people aged 25-30 years - an average of 16 per 1 min. Breathing depth determined by the volume of inhaled and exhaled air during one respiratory cycle. The product of the frequency of respiratory movements and their depth characterizes the basic value of external respiration - ventilation. A quantitative measure of pulmonary ventilation is the minute volume of breathing - this is the volume of air that a person inhales and exhales in 1 minute. The minute volume of a person's breathing at rest varies between 6-8 liters. During physical work, a person's minute breathing volume can increase 7-10 times.

Rice. 10.5. Volumes and capacities of air in the human lungs and the curve (spirogram) of changes in air volume in the lungs during quiet breathing, deep inhalation and exhalation. FRC - functional residual capacity.

Pulmonary air volumes. IN respiratory physiology a unified nomenclature of pulmonary volumes in humans has been adopted, which fill the lungs during quiet and deep breathing during the inhalation and exhalation phases of the respiratory cycle (Fig. 10.5). The lung volume that is inhaled or exhaled by a person during quiet breathing is called tidal volume. Its value during quiet breathing averages 500 ml. The maximum amount of air that a person can inhale above the tidal volume is called inspiratory reserve volume(average 3000 ml). The maximum amount of air that a person can exhale after a quiet exhalation is called the expiratory reserve volume (on average 1100 ml). Finally, the amount of air that remains in the lungs after maximum exhalation is called the residual volume, its value is approximately 1200 ml.

The sum of two or more pulmonary volumes is called pulmonary capacity. Air volume in human lungs it is characterized by inspiratory lung capacity, vital lung capacity and functional residual lung capacity. Inspiratory capacity (3500 ml) is the sum of tidal volume and inspiratory reserve volume. Vital capacity of the lungs(4600 ml) includes tidal volume and inspiratory and expiratory reserve volumes. Functional residual lung capacity(1600 ml) is the sum of expiratory reserve volume and residual lung volume. Sum vital capacity of the lungs And residual volume is called the total lung capacity, the average value of which in humans is 5700 ml.

When inhaling, the human lungs due to contraction of the diaphragm and external intercostal muscles, they begin to increase their volume from the level, and its value during quiet breathing is tidal volume, and with deep breathing - reaches different values reserve volume inhale. When exhaling, the volume of the lungs returns to the original level of functional function. residual capacity passively, due to elastic traction of the lungs. If air begins to enter the volume of exhaled air functional residual capacity, which occurs during deep breathing, as well as when coughing or sneezing, then exhalation is carried out by contracting the muscles of the abdominal wall. In this case, the value of intrapleural pressure, as a rule, becomes higher than atmospheric pressure, which determines the highest speed of air flow in the respiratory tract.

2. Spirography technique .

The study is carried out in the morning on an empty stomach. Before the study, the patient is recommended to remain calm for 30 minutes, and also stop taking bronchodilators no later than 12 hours before the start of the study.

The spirographic curve and pulmonary ventilation indicators are shown in Fig. 2.

Static indicators(determined during quiet breathing).

The main variables used to display the observed indicators of external respiration and to construct construct indicators are: the volume of respiratory gas flow, V (l) and time t ©. The relationships between these variables can be presented in the form of graphs or charts. All of them are spirograms.

A graph of the volume of flow of a mixture of respiratory gases versus time is called a spirogram: volume flow - time.

The graph of the relationship between the volumetric flow rate of a mixture of respiratory gases and the flow volume is called a spirogram: volumetric velocity flow - volume flow.

Measure tidal volume(DO) - the average volume of air that the patient inhales and exhales during normal breathing at rest. Normally it is 500-800 ml. The part of sediments that takes part in gas exchange is called alveolar volume(AO) and on average equals 2/3 of the DO value. The remainder (1/3 of the DO value) is functional dead space volume(FMP).

After a calm exhalation, the patient exhales as deeply as possible - measured expiratory reserve volume(ROvyd), which is normally 1000-1500 ml.

After a calm inhalation, the deepest possible breath is taken - measured inspiratory reserve volume(Rovd). When analyzing static indicators, it is calculated inspiratory capacity(Evd) - the sum of DO and Rovd, which characterizes the ability of lung tissue to stretch, as well as vital capacity(VC) - the maximum volume that can be inhaled after the deepest exhalation (the sum of DO, RO VD and Rovyd normally ranges from 3000 to 5000 ml).

After normal quiet breathing, a breathing maneuver is performed: the deepest possible breath is taken, and then the deepest, sharpest and longest (at least 6 s) exhalation is taken. This is how it is determined forced vital capacity(FVC) - the volume of air that can be exhaled during forced exhalation after maximum inspiration (normally 70-80% VC).

As the final stage of the study, recording is carried out maximum ventilation(MVL) - the maximum volume of air that can be ventilated by the lungs in 1 min. MVL characterizes the functional capacity of the external respiration apparatus and is normally 50-180 liters. A decrease in MVL is observed with a decrease in pulmonary volumes due to restrictive (limiting) and obstructive disorders of pulmonary ventilation.

When analyzing the spirographic curve obtained in the maneuver with forced exhalation, measure certain speed indicators (Fig. 3):

1) forced expiratory volume in the first second (FEV 1) - the volume of air that is exhaled in the first second with the fastest possible exhalation; it is measured in ml and calculated as a percentage of FVC; healthy people exhale at least 70% of FVC in the first second;

2) sample or Tiffno index- ratio of FEV 1 (ml)/VC (ml), multiplied by 100%; normally is at least 70-75%;

3) maximum volumetric air velocity at the expiratory level of 75% FVC (MOV 75) remaining in the lungs;

4) maximum volumetric air velocity at the expiratory level of 50% FVC (MOV 50) remaining in the lungs;

5) maximum volumetric air velocity at the expiratory level of 25% FVC (MOV 25) remaining in the lungs;

6) average forced expiratory volumetric flow rate, calculated in the measurement interval from 25 to 75% FVC (SES 25-75).

Symbols on the diagram.
Indicators of maximum forced expiration:
25 ÷ 75% FEV- volumetric flow rate in the average forced expiratory interval (between 25% and 75%
vital capacity of the lungs),
FEV1- flow volume during the first second of forced exhalation.

Rice. 3. Spirographic curve obtained in the forced expiratory maneuver. Calculation of FEV 1 and SOS 25-75 indicators

Calculation of speed indicators is of great importance in identifying signs of bronchial obstruction. A decrease in the Tiffno index and FEV 1 is a characteristic sign of diseases that are accompanied by a decrease in bronchial patency - bronchial asthma, chronic obstructive pulmonary disease, bronchiectasis, etc. MOS indicators are of the greatest value in diagnosing the initial manifestations of bronchial obstruction. SOS 25-75 reflects the state of patency of small bronchi and bronchioles. The latter indicator is more informative than FEV 1 for identifying early obstructive disorders.
Due to the fact that in Ukraine, Europe and the USA there is some difference in the designation of lung volumes, capacities and speed indicators that characterize pulmonary ventilation, we present the designations of these indicators in Russian and English (Table 1).

Table 1. Name of pulmonary ventilation indicators in Russian and English

Table 2. Name and correspondence of pulmonary ventilation indicators in different countries

All indicators of pulmonary ventilation are variable. They depend on gender, age, weight, height, body position, the state of the patient’s nervous system and other factors. Therefore, for a correct assessment of the functional state of pulmonary ventilation, the absolute value of one or another indicator is insufficient. It is necessary to compare the obtained absolute indicators with the corresponding values ​​in a healthy person of the same age, height, weight and gender - the so-called proper indicators. This comparison is expressed as a percentage relative to the proper indicator. Deviations exceeding 15-20% of the expected value are considered pathological.