The amount of air that the lungs can hold, i.e. contained in the lungs at the end of maximum inspiration is called total lung capacity (TLC). It consists of the residual air volume (RAV) remaining in the lungs after maximum exhalation and the vital capacity of the lungs.

Spirometry indicator: vital capacity of the lungs (inspiratory vital capacity)

Vital capacity, in turn, constitutes the tidal volume (TI), i.e. the volume of air inhaled and exhaled during each respiratory cycle, inspiratory reserve volume (IRV) - the volume that can be inhaled after a normal inhalation to the level of maximum inhalation, expiratory reserve volume (ERVSH) - the volume of air that can be exhaled from the position of quiet exhalation to the level maximum exhalation. Inhalation vital capacity is calculated as the difference in lung volume between a complete exhalation and a complete inhalation. RO EXP and RH add up to the functional residual capacity (FRC). Vital vital capacity is not an indicator of the functional capacity of the external respiration apparatus. At the same time, disruption of physiological processes can cause changes in lung volumes, so it is necessary to know them normal values and be able to assess deviations from the norm. The value of vital capacity depends mainly on gender, age and height (on body weight only insofar as it correlates with height).

Of greatest interest is not the absolute value of vital capacity, but its relationship to the standards developed taking into account the listed factors. To calculate the proper vital capacity (VC), nomograms, tables and formulas have been compiled. Preference should be given to the following formulas: JEL (l) is for men 25-60 years old 0.052 x P - 0.028 x B - 3.20, and for women of the same ages 0.049 x P - 0.019 x B - 3.76, where P is height (cm); B—age (years). It is believed that the actual vital capacity corresponds to the expected value if it differs from it by no more than ±15%, and the main practical significance is the reduction of the actual vital capacity (vital vital capacity more than 90% vital capacity is the norm, 90-85% vital capacity is the conditional norm, or the border zone ). Most often, a decrease in vital capacity is the result of an absolute decrease in the amount of functioning lung tissue(pulmonary edema, pneumonia, fibrosis, atelectasis, blockage of the main bronchus, etc.), less often - limited mobility chest, diaphragm.

An increase in vital capacity is usually observed in trained individuals (athletes, representatives of professions in which work requires significant physical stress) and is not a pathological sign.

Forced vital capacity (F expiratory vital capacity) is calculated as the difference in volume between the points of the beginning and end of forced expiration after the deepest possible inspiration.

Spirometry indicator FEV 1

FEV 1 - forced expiratory volume during the first second of the FVC maneuver, is the main criterion for diagnosing the presence of obstructive disorders; a decrease in FEV1 by 20% or more from normal indicates the presence of severe obstruction.

Spirometry indicator: Tiffno index

FEV 1/VC (Tiffno index) is expressed as a percentage and is a sensitive index of the presence or absence of bronchial obstruction. The proper value is considered to be 80% for men and 82% for women, the lower limit of the norm is 70%; conventional norm - 70-65%.

Spirometry indicator SOS 25-75 :

SOS25-75 - average volumetric expiratory flow rate, determined during exhalation from 25 to 75% of expiratory FVC, or the maximum average expiratory flow. The decrease in air flow speed is directly proportional to the degree of narrowing of the bronchial lumen. Impaired bronchial patency is possible due to its deformation by a tumor, silicotic conglomerates, accumulation of difficult to separate sputum, swelling of the bronchial wall, bronchospasm and due to other reasons in various combinations.

Spirometry indicator PIC

PSV - peak volumetric flow rate, the maximum flow achieved during exhalation of the first 20% of FVC. If the POS is determined later, this indicates that the maneuver was performed incorrectly, with a late development of the maximum force.

MOS spirometry indicator

MVR - instantaneous volumetric velocities, calculated at a certain exhalation volume. MOS25 is calculated at the time of exhalation 25% FVC, MOS50 at the time of exhalation 50% FVC, and MOS75 at the time of exhalation 75% FVC. A decrease in MOS, especially MOS50 and MOS75, indicates the presence of early expiratory disorders and is a valuable diagnostic criterion, since it is detected earlier than a decrease in FEV1.

Tpos is the time required to achieve POS. In healthy people, when the maneuver is performed correctly, Tpos does not exceed 0.1 s; with an increase in Tpos, we can talk about insufficient effort applied by the patient to perform forced exhalation.

TFVC - the time required to exhale 100 FVC of exhalation; if TFVC is less than 1 s, then this most likely indicates incomplete exhalation. An increase in TFVC is common with obstruction.

Currently, automatic spirometers are most often used to study FVD.

The study should be carried out in conditions of relative rest: in the morning or daytime, on an empty stomach or 2 hours after a small breakfast, after resting for 15 minutes, in a sitting position. To obtain undistorted values, it is necessary to discontinue bronchodilator therapy 12 hours before the study and quit smoking at least 2 hours before the study. Failure to comply with these conditions may affect the results obtained, which must be taken into account when interpreting them. When performing spirometry, the subject is in a sitting position, holding the spirometer mouthpiece in one hand, and a clamp is applied to the nose. After connecting to the device, the person performs 2-3 calm inhalations and exhalations to adapt to breathing into the device. Then, on command, a deep, complete exhalation is made from the level of calm breathing, and then a deep, calm inhalation, after which, without holding the breath, a full exhalation is performed with maximum effort, which must be achieved at the beginning of the maneuver and maintained throughout its entire duration. The study is repeated at least three times. The criterion for correct execution of maneuvers is the difference in results between attempts not exceeding 5%.

In order to more reliably judge the capacitance and velocity parameters of the respiratory function, the data obtained must be reduced to the conditions that existed in the lungs: at body temperature, ambient pressure and full saturation with water vapor, or BTPS. For this purpose, two corrections are made to take into account the change in volume with decreasing temperature and due to the condensation of water vapor during cooling. To simplify calculations, the correction factor can be calculated in advance (Table 12).

Table 12. Coefficients for converting gas volume to the BTPS system: BTPS - body temperature, pressure, saturated

Most modern spirometers allow you to determine the minute volume of respiration (MRV) - the volume of air that is ventilated in the lungs in 1 minute to provide the body with the necessary amount of oxygen and remove carbon dioxide. If breathing is uniform, then MOD is the product of the depth of breathing and its frequency; if it is uneven, then the MOD is equal to the sum of all tidal volumes per minute. The value of MOD depends on the body’s need for oxygen and the degree of utilization of ventilated air, i.e. on the amount of oxygen absorbed from a certain volume of air. The need for oxygen, even in the same person, varies dramatically depending on many factors, primarily physical activity. The degree of oxygen absorption from ventilated air also depends on many factors. Thus, MOR increases with deterioration of function cardiovascular system, disruption of the normal relationship between blood flow and ventilation, etc. The condition of the alveolar membrane is very important. In pneumosclerosis of toxic origin or pneumoconiosis, when the diffusion process is significantly hampered, an increase in ventilation occurs even if the body's need for oxygen remains unchanged.

The study is carried out under basal metabolic conditions: in the morning, on an empty stomach, after an hour's rest in a lying position, in a quiet, dimly lit room with a comfortable air temperature. Deviations from these strict conditions introduce significant changes in the results obtained. MOR is determined either by recording and subsequent processing of spirograms, or by measuring the volume of air exhaled over a known time using a gas meter or a large-capacity spirometer. The latter method is somewhat less accurate, but is quite accessible and quite widespread. Depending on the design of the device, a mask with a rubber gasket, pressed tightly to the face, or a mouthpiece is used; in the latter case, a clamp is applied to the nose. The advantage of using a mouthpiece is the significant reduction in dead space. The subject, in a sitting position, breathes calmly for several minutes until the amount of air exhaled per minute becomes the same. Even in healthy people, normal MOD values ​​vary widely (from 3 to 10 l) depending on gender, age, height, and body weight. Most often, in healthy men, the MOD is 5-7 l, in women it is slightly less. For a more accurate answer to the question of whether the actual MOD in a particular case corresponds to what it should, compare the resulting value, normalized to BTPS, with the amount of oxygen consumption, and if this is not possible, with the proper oxygen consumption. To establish the proper minute oxygen consumption (MOD) (the value of the proper basal metabolic rate divided by 7.07) should be divided by 40.

Spirometry indicator: h frequency and depth of breathing.

Depth of respiration can be measured using a spirograph or, although less accurately, a spirometer, and by dividing the MVR by the respiratory rate. Fluctuations in the depth of breathing even at rest can be significant (from 300 to 900 ml). In sick and untrained healthy people, an increase in ventilation often occurs with increased breathing and a decrease in its depth. Frequent and shallow breathing is ineffective, since the alveoli in this case are poorly ventilated, and the influence of “dead space” increases. Healthy and trained people breathe less often and deeper. Normally, the respiratory rate can range from 10 to 30 cycles per minute, but for most it is 16-18 and rarely exceeds 20.

Spirometry reading: m axial ventilation (MVL)

this is the maximum amount of air that can be ventilated in 1 minute. MVL is a very important dynamic indicator that gives an idea of ​​the amount of unused breathing reserves, the resistance that arises in the respiratory tract, etc. MVL can decrease during restrictive processes, mainly due to a decrease in vital capacity. A sharp decrease in MVL, not combined with an equally sharp decrease in vital capacity, as a rule, indicates an increase in respiratory resistance and indicates bronchial obstruction. Determining the reliable value of MVL is associated with some methodological difficulties. A significant influence on the result is exerted by the subject’s training, his ability to choose the optimal combination of frequency and depth of breathing, the need for a certain willpower. Research is carried out as follows. The patient is asked to breathe for 15 seconds at maximum frequency (40-60 times per minute) and depth. The result obtained is multiplied by 4, i.e. determine the volume of ventilation in 1 minute. If the study causes difficulties due to the patient’s condition, it can be carried out for 10 s and the result multiplied by 6. Then follows the reduction to BTPS conditions. DMVL is for men 25-60 years old DEL x 25 l min"1, and for women of the same age DEL x 26 l min"1, and values ​​​​of more than 85% are taken as the norm, and 85-75% as the conditional norm.

To assess the state of bronchial patency, it is possible to use pneumotachometry (PTM)

This is the determination of maximum (peak) air flow velocities. The indicators obtained during forced inhalation and exhalation are usually not quite accurately called the power of inhalation and exhalation (Min and Min). The study is performed using a pneumotachometer, from the tube of which, after maximum exhalation, a maximum inhalation (Min) is made, or after a maximum inhalation, a maximum exhalation (Min) is made into the tube. Tests are repeated 4-5 times at short intervals. The MVID is of greatest importance. Normally, its fluctuations within a wide range are noted (3.5-7.3 l s-1 in men and 3-5.9 l s-1 in women), which significantly complicates the interpretation of the results obtained. There are no generally accepted Mvyd standards. An approximate idea of ​​the appropriate value for a given subject can be obtained by multiplying the actual vital capacity by 1.2. However, the use of this technique does not always give reliable results. At the same time, the determination of Mvyd is very valuable when comparing the results of examination of the same patient during dynamic observation, when selecting optimal bronchodilators, as a screening during occupational examinations, etc.

To increase the diagnostic value of FVD studies, various tests are often used, which make it possible to clarify the mechanism of development of the identified changes. The bronchodilator test is used to determine the reversibility of obstruction and can be a valuable criterion in the differential diagnosis bronchial asthma and obstructive bronchitis. Provocative tests can reveal latent bronchospasm (test with methacholine), as well as the etiology of bronchospasm (test with physical activity, cold air, industrial allergens).

The main research method for assessing the condition of the bronchopulmonary system is spirography, interpretation of the results of which allows one to determine deviations and select the optimal treatment method. When performing a spirometric procedure, the obtained indicators are displayed in the spirogram - graphically and using established symbols. The necessary calculations are performed on the same device or using a special program on a computer. Understanding their essence helps not only the attending physician, but also the patient to monitor their condition and the effectiveness of treatment procedures.

Key indicators

During the process, the values ​​indicated in the table are measured.

The total number of parameters by which spirography itself is performed, deciphering and interpreting its results is much greater, since not only the listed values ​​are used to assess the bronchopulmonary system, but also their ratio in various combinations. In this case, the study is most often carried out purposefully, so one spirogram does not indicate all the available indicators, but only those that the test is aimed at. The most common are:

• vital capacity test;
• FVC test (Tiffno test);
• determination of maximum ventilation;
• frequency and depth of breathing;
• minute volume of respiration, etc.

In addition, a Post-BD examination may be prescribed, during which all specified values ​​are measured.

Explanation of meanings

The method used to decipher the spirogram is to compare the results obtained with normal values. In this case, the basic values ​​are calculated taking into account gender, height (P, cm) and age (B, number of full years) using the following formulas:

Pay attention! Normally, the main indicators should be more than 75–80% of the established values. If the examination result shows less than 70% of the standard parameters, this indicates the presence of pathology.

Spirography rates in the range of 70–80% are considered taking into account individual characteristics patient – ​​age, health status, constitution. In particular, for older people such spirography results may be the norm, but for a younger person they may indicate initial signs of obstruction.

The FEV1/VC ratio is called the Tiffno index. It is used to assess the degree of bronchial obstruction based on a bronchodilator test. An increase in indicators in this case is a sign of bronchospasm, a decrease indicates the presence of other mechanisms of obstruction.

In addition, one of the most commonly used indicators for assessing the condition of the bronchopulmonary system is the depth of breathing. It is measured by a spirograph or calculated by the ratio of MOR to respiratory rate (RR). This parameter varies significantly in a person even in a calm state, regardless of the presence of pathologies (within 300–1000 ml). With low physical fitness or the presence of respiratory dysfunction, increased ventilation of the lungs is usually achieved through rapid shallow breathing. It is characterized by low efficiency, since it does not provide adequate ventilation of the alveoli and leads to an increase in “dead space”. A healthy and trained person is characterized by infrequent deep breathing - an average of 20 cycles per minute.

Thus, after spirography has been performed, you can look at the results on the spirogram and understand the overall picture of the state of your bronchopulmonary system. But only a specialist can give a professional assessment of the severity of the pathology and the effect of the treatment on it.

» How is spirometry performed and what indicators correspond to the norm?

How is spirometry performed and what indicators correspond to the norm?

Spirometry is one of the studies that is used for pathologies of the bronchi and lungs. The method is painless and informative; it allows you to identify the type of respiratory tract insufficiency and make a preliminary diagnosis. Let's look at how spirometry is performed, what its indications and contraindications are, and how the results are interpreted.

The essence of the study

What spirometry is becomes clear from the name of the procedure: spiro meter translates as “breathing measurement.” During the examination, the doctor determines the speed and volume of breathing using a spirometer.

To better understand the essence of the method, you need to turn to anatomy respiratory system. Its 3 main elements are:

1. The respiratory tract allows air to pass through.
2. Lung tissue is responsible for gas exchange.
3. The chest works like a pump.

If the functions of any department are disrupted, it upsets the functioning of the lungs. Spirometry evaluates breathing parameters, which makes it possible to identify respiratory diseases, learn about the severity of pathologies and the effectiveness of therapy.

In addition to the name “spirography”, “spirometry” is also used. This means the same study. These designations differ only in that doctors understand spirography as a method of examining the respiratory organs, and spirography as a graphical recording of measurements made by a spirograph.

Indications

About spirometry we can say that this is a study that is widely used in medicine: in pulmonology for bronchitis and asthma, in allergology, in cardiology to differentiate pulmonary from cardiac dyspnea. The method is often used by anesthesiologists when preparing for surgery under general anesthesia.

Indications for the procedure:

• frequent ARVI;
• shortness of breath and persistent cough;
• lung problems identified by other methods;
• determining the causes of gas exchange disorders;
• allergy;
• early stage COPD (to monitor development and make a prognosis);
• preparation for surgery;
• examination of smokers' airways for obstruction if there are no symptoms;
• monitoring the condition of the lungs and bronchi during the treatment period;
• identifying the severity of breathing problems due to asthma, tuberculosis, etc.;
• diagnosis of respiratory failure;
• assessment of physical condition.

Preparing for a breath test

Preparation for spirometry is simple. It is carried out in the morning on an empty stomach, so you cannot eat enough. You can easily have breakfast 2 hours before the start, but not later.

Also, when preparing for the study you need:

• stop smoking several hours before the examination;
• do not drink coffee in the morning, you can replace it with juice;
• wear comfortable clothes that do not impede breathing;
• relax and come to your doctor's appointment in a calm state.

It is possible to temporarily stop some medications the patient is taking. The doctor will also ask if he has a pneumothorax or heart attack. This completes the patient's preparation.

How is the procedure performed?

The optimal time for spirometry is before 12 am. The procedure is carried out with a spirograph, which records changes.

The algorithm is as follows:

1. A disposable mouthpiece is attached to the spirograph.
2. The patient sits on a chair next to the device.
3. A nose clip is placed on the nose to allow breathing only through the mouth.
4. The patient is connected to the spirometer with a mouthpiece.
5. Inhalations and exhalations are performed following the doctor’s instructions.

Spirometry for patients is a painless and harmless procedure. The device automatically processes the data, so the results are shown to the patient after 5-10 minutes. after the examination. Next, the doctor analyzes the data and determines the localization of the problem.

Spirometry for bronchial asthma is often performed after taking medication to dilate the bronchi. This allows you to differentiate the disease from COPD and find out whether the obstruction has decreased.

For daily monitoring of their condition, asthma patients can use the pneumotachography method. It is simpler than spirography and is available for independent use. A device called a pneumotachograph is used. This is also a tube with replaceable mouthpieces that connect a person to a computing device. It automatically detects many breathing parameters. Carrying out such examinations at home will not only allow the patient to keep his health under control, but will also facilitate the work of the specialist: the results of pneumotachography show the dynamics of the disease in the intervals between visits to the clinic.

Features of spirometry in children

Spirometric testing is carried out in children from 5 years of age. He is no longer appointed younger age, since the rules for performing the procedure require taking a maximum breath. Otherwise, spirometry interpretation will be inaccurate.

At the adult level, a child can be examined from the age of 9 years. Before this, you need to try to create a positive atmosphere - with toys, affectionate attitude.

It is better for young patients to undergo spirometry in children's centers, and conventional laboratories do not adapt to their characteristics. Before the procedure, the child should be told in simple language how to inhale and exhale. For intense forced exhalation, images are sometimes used - for example, showing a candle on the screen, asking it to be blown out. The doctor should ensure that the baby's lips are pressed tightly against the mouthpiece. The protocol then indicates the number of successful cycles. Spirometry results are adjusted for age.

Research results

Spirometry indicators are the main source of information for diagnosing pulmonary diseases. The norms are average values ​​calculated based on the results of a survey of healthy people. They vary based on gender, age, height, weight and lifestyle.

Spirometry standards are given in the table:

Ventilation failure can be obstructive or restrictive. The first develops due to a decrease in the lumen of the bronchi with an increase in resistance to air flow. The second occurs due to a decrease in the ability of lung tissue to stretch.

When deciphering the results, the following parameters indicate the obstructive type:

• ELC is normal or higher;
• Tiffno index is underestimated;
• EOL increased.
• FEV 1 decreased.

With restrictive insufficiency, TLC decreases.

Contraindications

During the procedure, weakness and dizziness sometimes appear, which quickly disappear. An increase in pressure is also possible due to the load on the chest, since inhalation is made with effort.

Due to the possible deterioration of the patient's condition during spirometry, it is not prescribed in the following cases:

• surgeries on the eyes, sternum, and abdomen undergone during the last two months;
• pulmonary hemorrhage;
• metabolic disorders;
• heart attack or stroke that occurred less than a month ago;
• pneumothorax;
• uncontrolled hypertension;
• mental disorders;
• age less than 5 and more than 75 years.

Research is sometimes prescribed even if there are contraindications, but then doctors must be ready to provide emergency assistance to the patient.

Is it possible to fool a spirometer?

To work in hazardous conditions, you must undergo a medical examination, including spirometry. The ability to continue working depends on whether the indicators are normal. In such cases, some try to deceive the device and the doctor, but this is not easy to do. During the procedure, the patient exhales 3 times, and if the specialist’s instructions are followed, this reduces the risk of errors to a minimum.

Inaccuracies in spirography occur when incorrect information about age, height and weight is provided in an attempt to obtain normal values, and also when the procedure is violated if a person breathes with insufficient intensity or takes a shallow breath.

Spirometry is a safe and informative method for diagnosing pathologies of the lungs and bronchi. During the examination, breathing parameters are measured, which allows you to identify the disease or find out the effectiveness of medications. By providing reliable information about weight, height, age and following the procedure, the results are accurate and the risk of errors is minimal.

The respiratory rate (RR) is determined by the number of respiratory cycles recorded in one minute, which corresponds to a 50 mm horizontal segment of the spirogram. Normally, in a healthy adult, the number of respiratory movements is 16-20 per minute. RR depends on gender, age, profession, body position during the study. A physiological increase in breathing is observed when physical activity, emotional excitement, after a heavy meal.

An increase in respiratory rate in pathological conditions is observed:

a) with a decrease in the respiratory surface of the lungs: pneumonia, tuberculosis, collapse (atelectasis) of the lung due to its compression from the outside by liquid or gas, pneumosclerosis, fibrosis, pulmonary embolism, pulmonary edema;

b) with insufficient depth of breathing: difficulty contracting the intercostal muscles or diaphragm when sharp pain(dry pleurisy, acute myositis, intercostal neuralgia, rib fracture, development of tumor metastases in the ribs); a sharp increase in intra-abdominal pressure and a high position of the diaphragm (ascites, flatulence, late dates pregnancy, hysteria).

Pathological decrease in breathing observed when the respiratory center is depressed and its excitability is reduced (brain tumors, meningitis, cerebral hemorrhage, cerebral edema), when the respiratory center is exposed to toxic products due to their significant accumulation in the blood (uremia, hepatic coma, diabetic coma, some infectious diseases), with obstructive processes (bronchial asthma, chronic obstructive bronchitis, pulmonary emphysema).

Definition of DO(tidal volume) - the volume of air inhaled or exhaled during each normal respiratory cycle. The height of the respiratory wave is determined in millimeters and multiplied by the scale of the spirograph (20 or 40 ml depending on the type of spirograph). Normally, DO is 300-900 ml (average 500 ml).

A decrease in RR is usually combined with an increase in RR, and an increase in RR is usually combined with a decrease in RR (see reasons above). However, sometimes there can be a simultaneous decrease in DO and RR (sparse shallow breathing) with a sharp depression of the respiratory center, severe emphysema, a sharp narrowing of the glottis or trachea, or a simultaneous increase in DO and an increase in RR with high fever, severe anemia.

Determination of minute volume of respiration (MVR)

Amount of ventilated air per 1 min. MOD is determined by multiplying DO by breathing frequency: MOD (l) = DO (ml) x RR. If the respiratory waves are unequal, then the MRR is determined by summing up the DO in one minute. Normally, MOD ranges from 4-10 liters (average 5 liters). MVR is a measure of pulmonary ventilation, but not an absolute indicator of the effectiveness of alveolar ventilation; depends on the DO, BH and the amount of dead space. With the same MOP, alveolar ventilation can be different: frequent and shallow breathing is less rational, since a significant part of the inhaled air ventilates only the dead space without entering the alveoli, effective alveolar ventilation is reduced. With the same MOD indicators, but with slow and deep breathing, effective alveolar ventilation is much higher. Thus, the determination of the MRR, frequency and depth of breathing and the comparison of these indicators with each other and over time becomes of practical importance.

Determination of the proper MOD (DMOD)6 carried out according to the formula A.G. Dembo. The calculation is based on the proper basal metabolic rate, which is found using the table of Harris and Benedict. First, calculate DPO 2 using the formula: DPO 2 = DPO: 7.07 (coefficient 7.07 is the product of the thermal equivalent of 1 liter of oxygen, equal to 4.9, by the number of minutes per day - 1440 and divided by 1000). DMOD=DPO 2:40. IN normal conditions From every liter of ventilated air, 40 ml of oxygen is absorbed. MOD depends on the deterioration of the use of ventilated air, the difficulty of normal ventilation, disruption of gas diffusion processes, the body's need for O 2, and the intensity of metabolic processes.

MAUD increases:

a) when the body’s need for oxygen increases (degrees I and II of pulmonary and heart failure);

b) when increasing metabolic processes(thyrotoxicosis);

c) with some lesions of the central nervous system.

MOD decreases:

a) in case of severe III degree pulmonary or heart failure due to depletion of the body’s compensatory capabilities;

b) with a decrease in metabolic processes (myxedema);

c) when the respiratory center is depressed.

Determination of inspiratory reserve volume (IRV) - the maximum volume of air that a person can inhale after a normal breath. The height of the maximum inhalation wave (in mm) is measured from the level of quiet breathing and multiplied by the scale of the spirograph scale. Normal Department of Internal Affairs. equal to 1500-2000 ml. ROVD.= 45-55% VEL. The value of ROVD is of great practical importance. does not, since in healthy individuals it is subject to significant fluctuations. District Department of Internal Affairs decreases with a decrease in the respiratory surface of the lungs and in the presence of reasons that interfere with the maximum expansion of the lungs.

Determination of expiratory reserve volume (ERV) - the maximum volume of air that can be exhaled after a quiet exhalation. The magnitude of the maximum exhalation wave (in mm) is measured from the level of quiet exhalation and multiplied by the scale of the spirograph scale. Normal ROvyd. equal to 1500-2000 ml. ROvyd. is approximately 25-35% vital capacity. Due to significant variability, this indicator does not have much practical significance. Significant reduction in ROvyd. observed in obstructive processes (pulmonary emphysema, bronchial asthma, chronic obstructive bronchitis). With stenotic breathing, the proportion of ROvyd. in vital capacity increases.

Determination of vital capacity of the lungs (VC) - the maximum amount of air that can be exhaled after a maximum inhalation. VIC is the sum of DO, ROvd. and ROvyd. Vital = BEFORE + ROVD. + ROvyd.

When determining vital capacity using a spirogram, the distance from the top of the inspiratory knee (maximum inspiration) to the top of the expiratory knee (maximum exhalation) is measured in millimeters and multiplied by the scale of the spirograph. Normally, vital capacity ranges from 3000 to 5000 ml. Its value depends on age (up to 35 years it grows, then gradually decreases), gender (in women, vital capacity indicators are lower than in men), height, body weight, and body position. To correctly assess the results, it is necessary to determine the ratio of actual to expected vital capacity (VCL). To determine JEL, use the formulas:

JEL in l = 0.052xP-0.028xB-3.20 (for men);

VEL in l = 0.049xP-0.019xB-3.76 (for women);

where P is height, B is age.

The deviation of VC from VC should not exceed 15%. Therefore, it is of practical importance to reduce vital capacity below 85% of the expected value.

Vital capacity decreases:

a) when pathological conditions preventing maximum expansion of the lungs (exudative pleurisy, pneumothorax);

b) when the area of ​​functioning pulmonary parenchyma decreases, which is associated with changes in the lung tissue itself (pulmonary tuberculosis, pneumonia, pulmonary fibrosis, lung abscess, atelectasis, etc.);

c) when the elastic framework of the lungs is depleted (emphysema);

d) with extrapulmonary pathology: processes that limit the expansion of the chest (kyphoscoliosis, ankylosing spondylitis), limited mobility of the diaphragm, increased intra-abdominal pressure (ascites, flatulence, etc.);

e) for diseases of the cardiovascular system in the presence of congestion in the pulmonary circulation;

f) with severe general weakness;

g) in case of violation functional state nervous system.

Diagnostic value Vital vital capacity in a single study cannot be considered sufficient, however, in a comprehensive study of respiratory function, this indicator is very important both for calculations and comparison with other values, and for assessing the degree and type of respiratory failure (RF).

Determination of forced vital capacity (FVC) - the volume of air that can be exhaled after a maximum inhalation at the maximum possible speed. This indicator characterizes bronchial patency, elastic properties of the lungs, and the functionality of the respiratory muscles. Recording is performed at the maximum tape advance speed (600 mm/min or 1200 mm/min).

The FVC curve consists of two parts. The first part, which is recorded from the very beginning of exhalation, is characterized by a fast linear stroke and corresponds to the maximum and constant exhalation speed. Then the exhalation rate slows down, the curve becomes less steep and acquires a curvilinear course. The straight course of the FVC curve is caused by exhalation due to the elasticity of the lung tissue. Curvilinear vital capacity corresponds to the increasing force of the expiratory muscles.

FVC is determined by measuring the height of the curve from the top to its deepest part (in mm), followed by multiplication by the scale of the spirograph. Normally, FVC is 8-11% (100-300 ml) less than VC, mainly due to an increase in resistance to air flow in the small bronchi. If bronchial obstruction is impaired and air flow resistance increases, the difference increases to 1500 ml or more. This is observed in bronchial asthma, chronic obstructive bronchitis, and emphysema.

Determination of forced expiratory volume in 1 second (FEV 1) - the volume of air that the subject can exhale in the first second of a maximally forced exhalation. To determine this indicator on the FVC spirogram, from the zero mark corresponding to the beginning of exhalation, a segment equal to 1 second is set aside (1 cm at a tape pulling speed of 600 mm/min or 2 cm at a tape drive speed of 1200 mm/min). From the end of this segment it descends perpendicular to the intersection with the FVC curve, measure the height of the perpendicular in mm and multiply by the scale of the spirograph scale,

Normally, FEV 1 ranges from 1.4 to 4.2 l/sec. For a more correct assessment of the results, the ratio of actual FEV 1 to expected FEV 1 (DOFV 1) is determined. To calculate DOFV 1, the following formulas are used:

DOFV 1 =0.36xP-0.031x6-1.41 (for men);

DOFV 1 =0.026xP-0.028xB-0.36 (for women).

A decrease in FEV 1 below 75% DOFV 1 is of practical importance. The diagnostic significance of FEV 1 approximately corresponds to the significance of vital capacity, however, FEV 1 decreases to a greater extent during obstructive processes.

Definition of the Votchal-Tiffneau test. This indicator represents the relative one-second capacity, the percentage of FEV 1 to VC.

Tiffno test = FEV 1 / VC x 100%

Normally, the Tiffno test averages 70-90%. A decrease in the Tiffno test below 70% is considered pathological. The Tiffno test is of great importance in identifying obstructive processes in the lungs and is sharply reduced in bronchial asthma and emphysema.

To identify the role of bronchospasm in the occurrence of respiratory failure and reduce these indicators, pharmacological tests with bronchodilators (aminophylline, adrenaline, ephedrine, etc.) are used. FVC is recorded before and after administration of bronchodilators. If there are phenomena of bronchospasm after the administration of bronchodilators, the one-second capacity increases.

Determination of maximum pulmonary ventilation (MVL):(breathing limit, maximum tidal capacity, maximum minute volume).

MVL is the maximum amount of air that can be ventilated within a minute. Characterizes the functional ability of the external respiration apparatus.

Definition of MVL:

a) calculate the RR at maximum ventilation of the lungs (in 15 seconds), multiply this value by 4 and thus determine the RR during mechanical ventilation for 1 min;

b) determine DO at maximum ventilation. To do this, measure the size of the respiratory cycle in millimeters and multiply it by the spirograph scale;

c) multiply the BH by the DO (with MVL)

MVL in l = RR at MVL x DO at MVL.

Normally, MVL is in the range of 50-180 liters per minute. Its magnitude depends on the gender, age, height of the person being studied, and body position. To correctly assess the results obtained, it is necessary to bring the actual MFL to the proper one. For calculations use the formulas:

DMVL=JELx25 (for men);

DMVL=JELx26 (for women).

It is of practical importance to reduce the MVL below 75% of the expected value. MVL depends on muscle strength, compliance of the lungs and chest, and resistance to air flow. Its decrease is observed in processes accompanied by a decrease in lung compliance and impaired bronchial conduction. MVL decreases with various diseases lungs and heart failure. Its decrease increases as pulmonary or heart failure progresses. MVL is an indicator that subtly reacts to the state of the nervous system.

Determination of respiratory reserve (RR)

Breathing reserve indicates how much the patient can increase ventilation.

RD in l = MVL-MOD

RD in %DMVL = RD/MVL x 100%

RD in % MVL is one of the valuable indicators of the functional state of the external respiration apparatus. Normally, RD = 70-80 liters and exceeds MOD by no less than 15-20 times. RD=85-95% MVL.

RD decreases with respiratory and heart failure to 60-55% and below.

Related information.

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.

Indications for spirography the following:

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

2.Monitoring of 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 bronchodilators, short- and long-acting β2-agonists, anticholinergics), inhaled corticosteroids and membrane-stabilizing drugs.

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

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

6.Expertise of performance 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.

Rice. 1.

Despite its widespread clinical use, spirography is contraindicated in the following diseases and pathological conditions:

1. 1. heavy general condition patient, which does not allow the study to be carried out;
   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, which does not allow breathing maneuvers.

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 are determined during quiet breathing. Measure tidal volume (TO) - 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 (JSC) and on average equals 2/3 of the value of DO. The remainder (1/3 of the DO value) is the volume functional dead space (FMP). After a calm exhalation, the patient exhales as deeply as possible - measured expiratory reserve volume (ROVyd), which normally amounts to IOOO-1500 ml. After a calm inhalation, the deepest possible breath is taken - measured inspiratory reserve volume (District Department of Internal Affairs). When analyzing static indicators, the inspiratory capacity (Evd) is calculated - the sum of IR and IRvd, which characterizes the ability of lung tissue to stretch, as well as the vital capacity of the lungs ( vital capacity) - the maximum volume that can be inhaled after the deepest possible exhalation (the sum of DO, ROVD and ROVd 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% vital capacity). 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.

Rice. 2.

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

1) o forced expiratory volume in the first second (FEV1) - the volume of air that is exhaled in the first second during 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 FEV1 (ml)/VC (ml), multiplied by 100%; normally is at least 70-75%;

3) maximum volumetric air velocity at the expiratory level 75% FVC ( MOS75), remaining in the lungs; 4) maximum volumetric air velocity at the expiratory level of 50% FVC (MOC50) remaining in the lungs; 5) maximum volumetric air velocity at the expiratory level 25% FVC ( MOS25), remaining in the lungs; 6) average forced expiratory volumetric flow rate, calculated in the measurement interval from 25 to 75% FVC ( SOS25-75).

Rice. 3. Spirographic curve obtained in the forced expiratory maneuver. Calculation of FEV1 and SOS25-75 indicators

Calculation of speed indicators is of great importance in identifying signs of bronchial obstruction. Decrease Tiffno index and FEV1 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 diagnosis initial manifestations bronchial obstruction. SOS25-75 displays the state of patency of small bronchi and bronchioles. The latter indicator is more informative than FEV1 for identifying early obstructive disorders. The indicators PSV and MSV 75 reflect the patency of large bronchi, and MSV 50 and MSV 25 reflect the patency of small bronchi.

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 characterizing pulmonary ventilation, we provide the designations of these indicators in Russian and English languages(Table 1).
It should also be emphasized that there is identity in the indicators of volumetric expiratory flow rates in different countries (Table 2).

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

Closing volume (CV) is the volume of gas remaining in the lungs when the small airways begin to collapse during maximum exhalation (Mosby's Medical Dictionary, 8th edition. © 2009, Elsevier.).

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.

SPIROGRAPHY WITH REGISTRATION OF THE FLOW-VOLUME LOOP

Spirography with registration of the flow-volume loop - modern method study of pulmonary ventilation, which consists in determining the volumetric speed of air flow in the inhalation tract and its graphical display in the form of a “flow-volume” loop during quiet breathing of the patient and when he performs certain breathing maneuvers. Abroad this method is called spirometry . The purpose of the study is to diagnose the type and degree of pulmonary ventilation disorders based on the analysis of quantitative and qualitative changes in spirographic parameters.

Indications and contraindications for the use of spirometry similar to those for classical spirography.

Methodology . The study is carried out in the first half of the day, regardless of food intake. The patient is asked to close both nasal passages with a special clamp, take an individual sterilized mouthpiece into his mouth and tightly clasp his lips around it. The patient, in a sitting position, breathes through the tube along an open circuit, experiencing virtually no breathing resistance
The procedure for performing respiratory maneuvers with recording the flow-volume curve of forced breathing is identical to that performed when recording FVC during classical spirography. The patient should be explained that in a test with forced breathing one should exhale into the device as if one were to extinguish the candles on a birthday cake. After a period of quiet breathing, the patient takes a maximally deep breath, resulting in an elliptical curve (AEB curve) being recorded. Then the patient makes the fastest and most intense forced exhalation. In this case, a curve of a characteristic shape is recorded, which in healthy people resembles a triangle (Fig. 4).

Rice. 4. Normal loop (curve) of the relationship between the volumetric flow rate and air volume during breathing maneuvers. Inhalation begins at point A, exhalation begins at point B. POSV is recorded at point C. The maximum expiratory flow in the middle of the FVC corresponds to point D, the maximum inspiratory flow to point E

The maximum expiratory volumetric air flow rate is displayed by the initial part of the curve (point C, where the peak expiratory volumetric flow rate is recorded - POSP) - After this, the volumetric flow rate decreases (point D, where MOC50 is recorded), and the curve returns to its original position (point A). In this case, the flow-volume curve describes the relationship between the volumetric air flow rate and the pulmonary volume (lung capacity) during respiratory movements.
Data on speeds and volumes of air flow are processed by a personal computer thanks to adapted software. The flow-volume curve is displayed on the monitor screen and can be printed on paper, saved on magnetic media or in the memory of a personal computer.
Modern devices work with spirography sensors in an open system with subsequent integration of the air flow signal to obtain synchronous values ​​of lung volumes. The computer-calculated research results are printed together with the flow-volume curve on paper in absolute values ​​and as a percentage of the required values. In this case, FVC (air volume) is plotted on the abscissa axis, and air flow, measured in liters per second (l/s), is plotted on the ordinate axis (Fig. 5).

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Last name: Ident. number: 4132
Name:
Date of birth: 01/11/1957 Age: 47 Years
Gender: female Weight: 70 kg
Height: 165.0 cm

Rice. 5. Forced breathing flow-volume curve and pulmonary ventilation indicators in a healthy person

Rice. 6 Scheme of the FVC spirogram and the corresponding forced expiratory curve in “flow-volume” coordinates: V - volume axis; V" - flow axis

The flow-volume loop is the first derivative of the classical spirogram. Although the flow-volume curve contains essentially the same information as the classic spirogram, the visualization of the relationship between flow and volume allows deeper insight into functional characteristics both upper and lower respiratory tracts (Fig. 6). Calculation of highly informative indicators MOS25, MOS50, MOS75 using a classical spirogram has a number of technical difficulties when performing graphic images. Therefore, its results are not highly accurate. In this regard, it is better to determine the indicated indicators using the flow-volume curve.
Assessment of changes in speed spirographic indicators is carried out according to the degree of their deviation from the proper value. As a rule, for lower limit norms, the value of the flow indicator is accepted, which is 60% of the proper level.