Determination of the structure of the total lung capacity (TLC, or TLC). Body plethysmography and DLCO study - methodology and interpretation of results

Over the past 20-30 years, much attention has been paid to the study of lung function in patients with pulmonary pathology. A large number of physiological tests have been proposed to qualitatively or quantitatively determine the state of the function of the external respiration apparatus. Thanks to the existing system of functional studies, it is possible to identify the presence and degree of DN in various pathological conditions, find out the mechanism of respiratory failure. Functional lung tests allow you to determine the amount of lung reserves and the compensatory capabilities of the respiratory system. Functional studies can be used to quantify the changes that occur under the influence of various therapeutic effects(surgical interventions, therapeutic use of oxygen, bronchodilators, antibiotics, etc.), and therefore for an objective assessment of the effectiveness of these measures.

Functional research occupies a large place in practice. medical and labor expertise to determine the degree of disability.

General data on lung volumes The chest, which determines the boundaries of the possible expansion of the lungs, can be in four main positions, which determine the main volumes of air in the lungs.

1. During the period of calm breathing, the depth of breathing is determined by the volume of inhaled and exhaled air. The amount of air inhaled and exhaled during normal inhalation and exhalation is called the tidal volume (TO) (normally 400-600 ml; i.e. 18% VC).

2. At the maximum inhalation, an additional volume of air is introduced into the lungs - the inspiratory reserve volume (RIV), and at the maximum possible exhalation, the expiratory reserve volume (ERV) is determined.

3. Vital capacity of the lungs (VC) - the air that a person is able to exhale after a maximum breath.

VC = ROVd + TO + ROVd 4. After maximum exhalation, a certain amount of air remains in the lungs - the residual volume of the lungs (RLR).

5. Total lung capacity (TLC) includes VC and TRL, i.e., is the maximum lung capacity.

6. OOL + ROV = functional residual capacity (FRC), i.e., this is the volume that the lungs occupy at the end of a quiet exhalation. It is this capacity that largely includes alveolar air, the composition of which determines gas exchange with the blood of the pulmonary capillaries.

For a correct assessment of the actual indicators obtained during the examination, proper values ​​are used for comparison, i.e. theoretically calculated individual norms. When calculating due indicators, gender, height, weight, age are taken into account. When assessing, they usually calculate the percentage (%) of the actually obtained value to the due one. It should be taken into account that the volume of gas depends on atmospheric pressure, temperature of the medium and saturation with water vapor. Therefore, the measured lung volumes are corrected for barometric pressure, temperature and humidity at the time of the study. Currently, most researchers believe that indicators reflecting the volumetric values ​​of the gas must be reduced to body temperature (37 C), with full saturation with water vapor. This state is called BTPS (in Russian - TTND - body temperature, atmospheric pressure, saturation with water vapor).

When studying gas exchange, the resulting gas volumes lead to the so-called standard conditions (STPD) i.e. e. to a temperature of 0 C, a pressure of 760 mm Hg and dry gas (in Russian - STDS - standard temperature, atmospheric pressure and dry gas).

In mass surveys, an average correction factor is often used, which, for middle lane RF in the STPD system is taken equal to 0.9, in the BTPS system - 1. 1. For more accurate studies, special tables are used.

All lung volumes and capacities have a certain physiological significance. The volume of the lungs at the end of a quiet exhalation is determined by the ratio of two oppositely directed forces - the elastic traction of the lung tissue, directed inward (towards the center) and seeking to reduce the volume, and the elastic force of the chest, directed during quiet breathing mainly in the opposite direction - from the center outwards. The amount of air depends on many factors. First of all, the state of the lung tissue itself, its elasticity, the degree of blood filling, etc. matter. However, the volume of the chest, the mobility of the ribs, the state of the respiratory muscles, including the diaphragm, which is one of the main muscles that inhale, play a significant role.

The values ​​of lung volumes are affected by the position of the body, the degree of fatigue of the respiratory muscles, the excitability of the respiratory center and the state of nervous system.

Spirography is a method for assessing pulmonary ventilation with graphic registration respiratory movements, expressing changes in lung volume in time coordinates. The method is relatively simple, accessible, low burden and highly informative.

The main calculated indicators determined by spirograms

1. Frequency and rhythm of breathing. The number of breaths normally at rest ranges from 10 to 18-20 per minute. According to the spirogram of calm breathing with the rapid movement of the paper, one can determine the duration of the inhalation and exhalation phases and their relationship to each other. Normally, the ratio of inhalation and exhalation is 1: 1, 1: 1. 2; on spirographs and other devices, due to the high resistance during the exhalation period, this ratio can reach 1: 1. 3-1. 4. An increase in the duration of expiration increases with violations of bronchial patency and can be used in a comprehensive assessment of the function of external respiration. When evaluating the spirogram, in some cases, the rhythm of breathing and its disturbances matter. Persistent respiratory arrhythmias usually indicate dysfunction of the respiratory center.

2. Minute volume of breathing (MOD). MOD is the amount of ventilated air in the lungs in 1 min. This value is a measure of pulmonary ventilation. Its assessment should be carried out with the obligatory consideration of the depth and frequency of breathing, as well as in comparison with the minute volume of O 2. Although the MOD is not an absolute indicator of the effectiveness of alveolar ventilation (i.e., an indicator of the efficiency of circulation between the outside and alveolar air), the diagnostic value of this value is emphasized by a number of researchers (A. G. Dembo, Komro, etc.).

MOD \u003d DO x BH, where BH is the frequency of respiratory movements in 1 min DO - tidal volume

MOD under the influence of various influences can increase or decrease. An increase in MOD usually appears with DN. Its value also depends on the deterioration in the use of ventilated air, on difficulties in normal ventilation, on violations of the processes of diffusion of gases (their passage through membranes in the lung tissue), etc. An increase in MOD is observed with an increase in metabolic processes (thyrotoxicosis), with some CNS lesions. A decrease in MOD is noted in severe patients with pronounced pulmonary or heart failure, with depression of the respiratory center.

3. Minute oxygen uptake (MPO 2). Strictly speaking, this is an indicator of gas exchange, but its measurement and evaluation are closely related to the study of MOR. According to special methods, MPO 2 is calculated. Based on this, the oxygen utilization factor (KIO 2) is calculated - this is the number of milliliters of oxygen absorbed from 1 liter of ventilated air.

KIO 2 \u003d MPO 2 in ml MOD in l

Normal KIO 2 averages 40 ml (from 30 to 50 ml). A decrease in KIO 2 less than 30 ml indicates a decrease in ventilation efficiency. However, it must be remembered that with severe degrees of insufficiency of the function of external respiration, the MOD begins to decrease, since compensatory possibilities begin to be depleted, and gas exchange at rest continues to be ensured by the inclusion of additional circulatory mechanisms (polycythemia), etc. Therefore, the assessment of CIO 2 indicators, so same as the MOD, it is necessary to compare with clinical course underlying disease.

4. Vital capacity of the lungs (VC) VC is the volume of gas that can be exhaled with maximum effort after the deepest breath possible. The value of VC is influenced by the position of the body, therefore, at present, it is generally accepted to determine this indicator in the patient's sitting position.

The study should be carried out at rest, i.e., 1.5-2 hours after a light meal and after 10-20 minutes of rest. Various types of water and dry spirometers, gas meters and spirographs are used to determine VC.

When recorded on a spirograph, VC is determined by the amount of air from the moment of the deepest breath to the end of the strongest exhalation. The test is repeated three times with rest intervals, the largest value is taken into account.

VC, in addition to the usual technique, can be recorded two-stage, i.e. after a calm exhalation, the subject is asked to take the deepest possible breath and return to the level of calm breathing, and then exhale as much as possible.

For a correct assessment of the actually received VC, the calculation of the due VC (JEL) is used. The most widely used is the calculation according to the Anthony formula:

JEL \u003d DOO x 2.6 for men JEL \u003d DOO x 2.4 for women, where DOO is the proper basal exchange, is determined according to special tables.

When using this formula, it must be remembered that the values ​​of the DOC are determined under STPD conditions.

The formula proposed by Bouldin et al. has received recognition: 27.63 - (0.112 x age in years) x height in cm (for men)21. 78 - (0.101 x age in years) x height in cm (for women) The All-Russian Research Institute of Pulmonology offers JEL in liters in the BTPS system to calculate using the following formulas: 0.052 x height in cm - 0.029 x age - 3.2 (for men)0. 049 x height in cm - 0. 019 x age - 3.9 (for women) When calculating JEL, nomograms and calculation tables have found their application.

Evaluation of the data obtained: 1. Data deviating from the proper value by more than 12% in men and - 15% in women should be considered reduced: normally, such values ​​occur only in 10% of practically healthy individuals. Having no right to consider such indicators as obviously pathological, it is necessary to assess the functional state of the respiratory apparatus as reduced.

2. Data deviating from the proper values ​​by 25% in men and 30% in women should be considered as very low and considered a clear sign of a pronounced decrease in function, because normally such deviations occur in only 2% of the population.

Pathological conditions that prevent the maximum expansion of the lungs (pleurisy, pneumothorax, etc.), changes in the lung tissue itself (pneumonia, lung abscess, tuberculous process) and causes not associated with pulmonary pathology (limited diaphragm mobility, ascites, etc.). The above processes are changes in the function of external respiration according to the restrictive type. The degree of these violations can be expressed by the formula:

VC x 100% VC 100-120% - normal values ​​100-70% - restrictive disorders of moderate severity 70-50% - restrictive disorders of significant severity less than 50% - pronounced disorders of the obstructive type functional state of the nervous system, general state sick. A pronounced decrease in VC is observed in diseases of cardio-vascular system and is largely due to stagnation in the pulmonary circulation.

5. Focused vital capacity (FVC) To determine FVC, spirographs with high pulling speeds (from 10 to 50-60 mm/s) are used. Preliminary research and recording of VC is carried out. After a short rest, the subject takes the deepest possible breath, holds his breath for a few seconds, and performs maximum exhalation(forced exhalation).

There are various ways to assess FVC. However, the definition of one-second, two- and three-second capacity, that is, the calculation of the volume of air in 1, 2, 3 seconds, has received the greatest recognition from us. The one-second test is more commonly used.

Normally, the duration of exhalation in healthy people is from 2.5 to 4 seconds. , somewhat delayed only in the elderly.

According to a number of researchers (B. S. Agov, G. P. Khlopova, and others), valuable data are provided not only by the analysis of quantitative indicators, but also by the qualitative characteristics of the spirogram. Different parts of the forced expiratory curve have different diagnostic value. The initial part of the curve characterizes the resistance of large bronchi, which account for 80% of the total bronchial resistance. The final part of the curve, which reflects the state of the small bronchi, unfortunately does not have an exact quantitative expression due to poor reproducibility, but is one of the important descriptive features of the spirogram. AT last years devices “peak-fluorimeters” have been developed and put into practice, which make it possible to more accurately characterize the state of the distal section of the bronchial tree. being small in size, they allow to monitor the degree of bronchial obstruction in patients with bronchial asthma, to use drugs in a timely manner, before the appearance of subjective symptoms of bronchospasm.

A healthy person exhales in 1 second. approximately 83% of their vital lung capacity, in 2 seconds. - 94%, in 3 sec. - 97%. Exhalation in the first second of less than 70% always indicates pathology.

signs respiratory failure obstructive type:

FZhEL x 100% (Tiffno index) VC up to 70% - normal 65-50% - moderate 50-40% - significant less than 40% - sharp

6. Maximum ventilation of the lungs (MVL). In the literature, this indicator is found under various names: the limit of breathing (Yu. N. Shteingrad, Knippint, etc.), the limit of ventilation (M. I. Anichkov, L. M. Tushinskaya, etc.).

AT practical work the definition of MVL by spirogram is more often used. The most widely used method for determining MVL by arbitrary forced (deep) breathing with the maximum available frequency. In a spirographic study, the recording begins with a calm breath (until the level is established). Then the subject is asked to breathe into the apparatus for 10-15 seconds with the maximum possible speed and depth.

The magnitude of MVL in healthy people depends on height, age, and sex. It is influenced by the occupation, fitness and general condition of the subject. MVL largely depends on the willpower of the subject. Therefore, for the purposes of standardization, some researchers recommend performing MVL with a breathing depth of 1/3 to 1/2 VC with a respiratory rate of at least 30 per minute.

The average MVL figures in healthy people are 80-120 liters per minute (i.e., this is the largest amount of air that can be ventilated through the lungs with the deepest and most frequent breathing in one minute). MVL changes both during obsiructive processes and during restriction, the degree of violation can be calculated by the formula:

MVL x 100% 120-80% - normal indicators of DMVL 80-50% - moderate violations 50-35% - significant less than 35% - pronounced violations

Various formulas for determining due MVL (DMVL) have been proposed. The most widespread definition of DMVL, which is based on the Peaboda formula, but with an increase in the 1/3 JEL proposed by him to 1/2 JEL (A. G. Dembo).

Thus, DMVL \u003d 1/2 JEL x 35, where 35 is the respiratory rate in 1 minute.

DMVL can be calculated based on the body surface area (S), taking into account age (Yu. I. Mukharlyamov, A. I. Agranovich).

To calculate DMVL, the Gaubats formula is satisfactory: DMVL \u003d JEL x 22 for people under 45 years old DMVL \u003d JEL x 17 for people over 45 years old

7. Residual volume (RVR) and functional residual lung capacity (FRC). TRL is the only indicator that cannot be studied by direct spirography; to determine it, additional special gas analytical instruments (POOL-1, nitrogenograph) are used. Using this method, the FRC value is obtained, and using the VC and ROvyd. , calculate OOL, OEL and OEL/OEL.

OOL \u003d FOE - ROVyd DOEL \u003d JEL x 1. 32, where DOEL is the proper total lung capacity.

The value of FOE and OOL is very high. With an increase in the OOL, the uniform mixing of the inhaled air is disturbed, and the ventilation efficiency decreases. OOL increases with emphysema, bronchial asthma.

FFU and OOL decrease with pneumosclerosis, pleurisy, pneumonia.

Limits of the norm and gradations of deviation from the norm of respiratory parameters

The earliest and most pronounced changes in respiratory function in patients with asthma, they are observed in the ventilation link, which affects bronchial patency and the structure of lung volumes. These changes increase depending on the phase and severity of BA. Even with a mild course of BA in the phase of exacerbation of the disease, there is a significant deterioration in bronchial patency with its improvement in the remission phase, but without complete normalization. The greatest violations are observed in patients at the height of an asthma attack and, especially, in asthmatic status (Raw reaches more than 20 cm of water column, SGaw is less than 0.01 cm of water column, and FEV is less than 15% of due). Raw in BA increases both during inhalation and exhalation, which does not allow a clear differentiation of BA from COB. The most characteristic feature of BA should be considered not so much the transient nature of obstruction as its lability, which manifests itself both during the day and in seasonal fluctuations.

Bronchial obstruction are usually combined with a change in the OEL and its structure. This is manifested by a shift in the level of functional residual capacity (FRC) to the inspiratory area, a slight increase in the RCL and a regular increase in the RCL, which sometimes reaches 300-400% of the proper value during exacerbation of BA. In the early stages of the disease, VC does not change, but with the development of pronounced changes, it clearly decreases, and then TOL/TOL can reach 75% or more.

When using bronchodilators there was a clear dynamics of the studied parameters with their almost complete normalization in the remission phase, which indicates a decrease in bronchomotor tone.

In patients with BA more often than in other lung pathologies, both in the interictal period and in the remission phase, general alveolar hyperventilation is observed with clear signs of its uneven distribution and inadequacy to pulmonary blood flow. This hyperventilation is associated with excessive stimulation of the respiratory center from the cortex and subcortical structures, irritant and mechanoreceptors of the lungs and respiratory muscles, due to impaired control of bronchial tone and respiratory mechanics in patients with asthma. First of all, there is an increase in the ventilation of the functional dead space. Alveolar hypoventilation is more often observed with severe attacks of suffocation, it is usually accompanied by severe hypoxemia and hypercapnia. The latter can reach 92.1 + 7.5 mm Hg. at stage III of asthmatic status.

With absence signs of development of pneumofibrosis and emphysema of the lungs in patients with asthma, there is no decrease in the diffusion capacity of the lungs and its components (according to the breath-holding method according to CO) either during an asthma attack or in the interictal period. After the use of bronchodilators, against the background of a significant improvement in the state of bronchial patency and the structure of the RFE, there is often a decrease in the diffusion capacity of the lungs, an increase in ventilation-perfusion unevenness and hypoxemia due to the inclusion of a larger number of hypoventilated alveoli in ventilation.

FVD has its own characteristics in patients with chronic suppurative lung diseases, the outcome of which is to some extent pronounced destructive changes in the lungs. Chronic suppurative lung diseases include bronchiectasis, chronic abscesses, cystic hypoplasia of the lungs. The development of bronchiectasis, as a rule, is facilitated by a violation of bronchial patency and inflammation of the bronchi. The presence of a focus of infection inevitably leads to the development of bronchitis, in connection with which violations of respiratory function are largely associated. Moreover, the severity of ventilation disorders directly depends on the volume of bronchial damage. The most characteristic functional changes in bronchiectasis are mixed or obstructive. Restrictive violations occur in only 15-20% of cases. In the pathogenesis of violations of bronchial patency, the main role is played by edematous-inflammatory changes in the bronchial tree: edema, hypertrophy of the mucosa, accumulation of pathological contents in the bronchi. In about half of the patients, bronchospasm also plays a role. With a combination of bronchiectasis with pneumosclerosis, emphysema, pleural adhesions, changes in the mechanics of breathing become even more heterogeneous. Lung compliance is often reduced. There is an increase in OOL and the ratio of OOL / OEL. Increasing uneven ventilation. More than half of the patients have impaired lung diffusion, and the severity of hypoxemia at the onset of the disease is low. The acid-base state usually corresponds to metabolic acidosis.

In chronic abscess violations of respiratory function practically do not differ from respiratory disorders in bronchiectasis.

With cystic underdevelopment of the bronchi more pronounced violations of bronchial patency and a lesser severity of diffusion disorders are revealed than with acquired bronchiectasis, which indicates a good compensation for this defect and the limited nature of the inflammatory process.

One of the main methods for assessing the ventilation function of the lungs, used in the practice of medical and labor examination, is spirography, which allows determining statistical lung volumes - lung capacity (VC), functional residual capacity (FRC), residual lung volume (RLV), total lung capacity (TLC).

Knowing FFU, you can calculate the residual volume by subtracting the expiratory reserve volume from it. Then calculate total lung capacity, adding up OOL and ZHEL. Normally, the TEL is from 4 to 7 liters. There are several formulas for calculating OEL d olzhnoy. The most accurate formulas are Baldwin and co-authors:

DOEL\u003d (36.2 - 0.06) x age x height in cm (for men);

DOEL\u003d (28.6 - 0.06) x age x height in cm (for women).

Normal values OEL- within DOEL± 20%, going beyond this range is considered as a pathology:

±20-35% - moderate pathology,
±35-50% - significant,
more than ±50% - sharp.

Of particular interest is the proportion residual volume lungs in total lung capacity. The normal values ​​reported by different authors fluctuate around the figure of 25-30%, increasing to 35% by the age of 50-60.

An increase in these values ​​within the limits of up to 10% is considered as an upward trend: from ±10 to ±20% - a moderate increase, from 20 to 30% - a significant increase, more than 30% - sharp increase OOL.

By size OOL / OEL one can judge both the elasticity of the lungs and bronchial patency. This is due to the nature of the sample. At healthy person the expiratory limit is determined by the possibilities of compression of the rib cage. With emphysema, due to the insufficiency of the elastic structures of the lung parenchyma, the alveolar walls collapse, leading to the closure of inhalation into the bronchioles. Part of the air is blocked in the emphysematous alveolar sacs and loses communication with the bronchi.

A similar picture is observed in violation of bronchial patency, when under the influence of high intrathoracic pressure during deep expiration, the walls of the bronchi subside before exhalation ends. With tracheobronchial dyskinesias, which are associated with a decrease in the tone of the membranous part of the wall of the trachea and large bronchi, on expiration there is a narrowing and complete overlap in this area. Exhalation stops, the expiratory reserve volume is small.

All these phenomena are accompanied by an increase residual volume and such a restructuring OEL, at which VC is reduced, and OOL- enlarged. If normal in a young healthy person OOL takes 25% OEL, a FFU- 50%, then with emphysema FFU takes 70-80% OEL and consists almost entirely of OOL, and the expiratory reserve volume is absent or sharply reduced. However, it should be noted that the increase OOL / OEL, pathognomonic for emphysema, can also be observed with reversible violations of bronchial patency, for example, during an attack of bronchial asthma, in which case we are talking about acute swelling of the lungs.

Medical rehabilitation / Ed. V. M. Bogolyubov. Book I. - M., 2010. S. 38-39.

A number of methods are used to diagnose respiratory failure. modern methods studies that allow to get an idea of ​​the specific causes, mechanisms and severity of the course of respiratory failure, concomitant functional and organic changes internal organs, hemodynamic state, acid-base state, etc. For this purpose, the function of external respiration, blood gas composition, respiratory and minute ventilation volumes, hemoglobin and hematocrit levels, blood oxygen saturation, arterial and central venous pressure, heart rate, ECG, and, if necessary, wedge pressure are determined. pulmonary artery(DZLA), conduct echocardiography and others (A.P. Zilber).

Assessment of respiratory function

The most important method for diagnosing respiratory failure is the assessment of the respiratory function of the respiratory function), the main tasks of which can be formulated as follows:

1. Diagnosis of violations of the function of external respiration and an objective assessment of the severity of respiratory failure.
2. Differential diagnosis of obstructive and restrictive disorders of pulmonary ventilation.
3. Substantiation of pathogenetic therapy of respiratory failure.
4. Evaluation of the effectiveness of the treatment.

These tasks are solved using a number of instrumental and laboratory methods: pyrometry, spirography, pneumotachometry, tests for the diffusion capacity of the lungs, impaired ventilation-perfusion relations, etc. The volume of examinations is determined by many factors, including the severity of the patient's condition and the possibility (and expediency!) a full and comprehensive study of FVD.

The most common methods for studying the function of external respiration are spirometry and spirography. Spirography provides not only a measurement, but a graphical recording of the main indicators of ventilation during calm and shaped breathing, physical activity, carrying out pharmacological tests. In recent years, the use of computer spirographic systems has greatly simplified and accelerated the examination and, most importantly, made it possible to measure the volumetric velocity of inspiratory and expiratory air flows as a function of lung volume, i.e. analyze the flow-volume loop. Such computer systems include, for example, spirographs manufactured by Fukuda (Japan) and Erich Eger (Germany) and others.

Research methodology. The simplest spirograph consists of a double cylinder filled with air, immersed in a container of water and connected to a device to be registered (for example, a drum calibrated and rotating at a certain speed, on which the readings of the spirograph are recorded). The patient in a sitting position breathes through a tube connected to an air cylinder. Changes in lung volume during respiration are recorded by a change in the volume of a cylinder connected to a rotating drum. The study is usually carried out in two modes:

• In the conditions of the main exchange - in the early morning hours, on an empty stomach, after a 1-hour rest in the supine position; 12-24 hours before the study, medication should be stopped.
• In conditions of relative rest - in the morning or afternoon, on an empty stomach or not earlier than 2 hours after a light breakfast; before the study, rest for 15 minutes in a sitting position is necessary.

The study is carried out in a separate dimly lit room with an air temperature of 18-24 C, after familiarizing the patient with the procedure. When conducting a study, it is important to achieve full contact with the patient, since his negative attitude towards the procedure and the lack of necessary skills can significantly change the results and lead to an inadequate assessment of the data obtained.

The main indicators of pulmonary ventilation

Classical spirography allows you to determine:

1. the value of most lung volumes and capacities,
2. main indicators of pulmonary ventilation,
3. oxygen consumption by the body and ventilation efficiency.

There are 4 primary lung volumes and 4 containers. The latter include two or more primary volumes.

lung volumes

1. Tidal volume (TO, or VT - tidal volume) is the volume of gas inhaled and exhaled during quiet breathing.
2. Inspiratory reserve volume (RO vd, or IRV - inspiratory reserve volume) - the maximum amount of gas that can be additionally inhaled after a quiet breath.
3. Expiratory reserve volume (RO vyd, or ERV - expiratory reserve volume) - the maximum amount of gas that can be additionally exhaled after a quiet exhalation.
4. Residual lung volume (OOJI, or RV - residual volume) - the volume of reptile remaining in the lungs after maximum exhalation.

lung capacity

1. The vital capacity of the lungs (VC, or VC - vital capacity) is the sum of TO, RO vd and RO vyd, i.e. the maximum volume of gas that can be exhaled after a maximum deep breath.
2. Inspiratory capacity (Evd, or 1C - inspiratory capacity) is the sum of TO and RO vd, i.e. the maximum volume of gas that can be inhaled after a quiet exhalation. This capacity characterizes the ability of lung tissue to stretch.
3. Functional residual capacity (FRC, or FRC - functional residual capacity) is the sum of OOL and PO vyd i.e. the amount of gas remaining in the lungs after a quiet exhalation.
4. The total lung capacity (TLC, or TLC - total lung capacity) is the total amount of gas contained in the lungs after a maximum breath.

Ordinary spirographs, widely used in clinical practice, allow you to determine only 5 lung volumes and capacities: DO, RO vd, RO vyd. VC, Evd (or, respectively, VT, IRV, ERV, VC and 1C). To find the most important indicator of lung ventilation - functional residual capacity (FRC, or FRC) and calculate the residual lung volume (ROL, or RV) and total lung capacity (TLC, or TLC), it is necessary to apply special techniques, in particular, helium dilution methods, flushing nitrogen or whole body plethysmography (see below).

The main indicator in the traditional method of spirography is the vital capacity of the lungs (VC, or VC). To measure VC, the patient, after a period of quiet breathing (TO), first takes a maximum breath, and then, possibly, a full exhalation. In this case, it is advisable to evaluate not only the integral value of VC) and inspiratory and expiratory vital capacity (VCin, VCex, respectively), i.e. the maximum volume of air that can be inhaled or exhaled.

The second obligatory method used in traditional spirography is a test with the determination of forced (expiratory) vital capacity of the lungs OGEL, or FVC - forced vital capacity expiratory), which allows you to determine the most (formative speed indicators of pulmonary ventilation during forced exhalation, characterizing, in particular, the degree Intrapulmonary airway obstruction As with the VC test, the patient inhales as deeply as possible, and then, in contrast to the VC determination, exhales the air as fast as possible (forced expiration), which registers a gradually flattening exponential curve. Evaluating the spirogram of this expiratory maneuver, several indicators are calculated:

1. Forced expiratory volume in one second (FEV1, or FEV1 - forced expiratory volume after 1 second) - the amount of air removed from the lungs in the first second of exhalation. This indicator decreases both with airway obstruction (due to an increase in bronchial resistance) and with restrictive disorders (due to a decrease in all lung volumes).
2. Tiffno index (FEV1 / FVC,%) - the ratio of forced expiratory volume in the first second (FEV1 or FEV1) to forced vital capacity (FVC, or FVC). This is the main indicator of the expiratory maneuver with forced exhalation. It decreases significantly in broncho-obstructive syndrome, since the slowing of exhalation due to bronchial obstruction is accompanied by a decrease in forced expiratory volume in 1 s (FEV1 or FEV1) in the absence or slight decrease general meaning FZhEL (FVC). With restrictive disorders, the Tiffno index practically does not change, since FEV1 (FEV1) and FVC (FVC) decrease almost to the same extent.
3. Maximum expiratory flow rate at 25%, 50% and 75% of forced vital capacity . These indicators are calculated by dividing the corresponding forced expiratory volumes (in liters) (at the level of 25%, 50% and 75% of total FVC) by the time to reach these volumes during forced exhalation (in seconds).
4. Mean expiratory flow rate at 25~75% of FVC (COC25-75% or FEF25-75). This indicator is less dependent on the patient's voluntary effort and more objectively reflects bronchial patency.
5. Peak volumetric forced expiratory flow rate (POS vyd, or PEF - peak expiratory flow) - the maximum volumetric forced expiratory flow rate.

Based on the results of the spirographic study, the following are also calculated:

1. the number of respiratory movements during quiet breathing (RR, or BF - breathing freguency) and
2. minute volume of breathing (MOD, or MV - minute volume) - the amount of total ventilation of the lungs per minute with calm breathing.

Investigation of the flow-volume relationship

Computer spirography

Modern computer spirographic systems allow you to automatically analyze not only the above spirographic indicators, but also the flow-volume ratio, i.e. dependence of the volume flow rate of air during inhalation and exhalation on the value of lung volume. Automatic computer analysis of the inspiratory and expiratory flow-volume loop is the most promising method for quantifying pulmonary ventilation disorders. Although the flow-volume loop itself contains much of the same information as a simple spirogram, the visibility of the relationship between volumetric airflow rate and lung volume allows a more detailed study of the functional characteristics of both the upper and lower airways.

The main element of all modern spirographic computer systems is a pneumotachographic sensor that registers the volumetric air flow rate. The sensor is a wide tube through which the patient breathes freely. In this case, as a result of a small, previously known, aerodynamic resistance of the tube between its beginning and end, a certain pressure difference is created, which is directly proportional to the volumetric air flow rate. Thus, it is possible to register changes in the volumetric flow rate of air during inhalation and exhalation - pneumotachogram.

Automatic integration of this signal also makes it possible to obtain traditional spirographic indicators - lung volume values ​​in liters. Thus, at each moment of time, information about the volumetric air flow rate and about the volume of the lungs at a given moment of time simultaneously enters the computer's memory device. This allows a flow-volume curve to be plotted on the monitor screen. A significant advantage of this method is that the device operates in an open system, i.e. the subject breathes through the tube along an open circuit, without experiencing additional resistance to breathing, as in conventional spirography.

The procedure for performing breathing maneuvers when registering a flow-volume curve is similar to writing a normal coroutine. After a period of compound breathing, the patient delivers a maximum breath, resulting in the inspiratory portion of the flow-volume curve being recorded. The volume of the lung at point "3" corresponds to the total lung capacity (TLC, or TLC). Following this, the patient performs a forced expiration, and the expiratory part of the flow-volume curve (“3-4-5-1” curve) is recorded on the monitor screen. reaching a peak (peak volumetric velocity - POS vyd, or PEF), and then decreases linearly until the end of the forced exhalation, when the forced exhalation curve returns to its original position.

In a healthy person, the shape of the inspiratory and expiratory parts of the flow-volume curve differ significantly from each other: the maximum volumetric flow rate during inspiration is reached at about 50% VC (MOS50%inspiration > or MIF50), while during forced expiration, the peak expiratory flow ( POSvyd or PEF) occurs very early. The maximum inspiratory flow (MOS50% of inspiration, or MIF50) is about 1.5 times the maximum expiratory flow at mid-vital capacity (Vmax50%).

The described flow-volume curve test is carried out several times until a concurrence of results is obtained. In most modern instruments, the procedure for collecting the best curve for further processing of the material is carried out automatically. The flow-volume curve is printed along with multiple pulmonary ventilation measurements.

Using a pneumotochographic sensor, the curve of the volumetric air flow rate is recorded. Automatic integration of this curve makes it possible to obtain a tidal volume curve.

Evaluation of the results of the study

Most lung volumes and capacities, as in healthy patients, and in patients with lung diseases, depend on a number of factors, including age, gender, chest size, body position, fitness level, etc. For example, the vital capacity of the lungs (VC, or VC) in healthy people decreases with age, while the residual volume of the lungs (ROL, or RV) increases, and the total lung capacity (TLC, or TLC) practically does not change. VC is proportional to the size of the chest and, accordingly, the height of the patient. In women, VC is on average 25% lower than in men.

Therefore, from a practical point of view, it is not advisable to compare the values ​​​​of lung volumes and capacities obtained during a spirographic study: with single “standards”, the fluctuations in the values ​​\u200b\u200bof which due to the influence of the above and other factors are very significant (for example, VC normally can range from 3 to 6 l) .

The most acceptable way to evaluate the spirographic indicators obtained during the study is to compare them with the so-called due values, which were obtained when examining large groups of healthy people, taking into account their age, sex and height.

Proper values ​​of ventilation indicators are determined by special formulas or tables. In modern computer spirographs, they are calculated automatically. Boundaries are given for each indicator normal values as a percentage in relation to the calculated due value. For example, VC (VC) or FVC (FVC) is considered reduced if its actual value is less than 85% of the calculated proper value. A decrease in FEV1 (FEV1) is stated if the actual value of this indicator is less than 75% of the due value, and a decrease in FEV1 / FVC (FEV1 / FVC) - if the actual value is less than 65% of the due value.

Limits of normal values ​​of the main spirographic indicators (as a percentage in relation to the calculated proper value).

In addition, when evaluating the results of spirography, it is necessary to take into account some additional conditions under which the study was carried out: the levels of atmospheric pressure, temperature and humidity of the surrounding air. Indeed, the volume of air exhaled by the patient usually turns out to be somewhat less than that which the same air occupied in the lungs, since its temperature and humidity, as a rule, are higher than those of the surrounding air. To exclude differences in the measured values ​​associated with the conditions of the study, all lung volumes, both due (calculated) and actual (measured in this patient), are given for conditions corresponding to their values ​​at a body temperature of 37 ° C and full saturation with water. in pairs (BTPS system - Body Temperature, Pressure, Saturated). In modern computer spirographs, such a correction and recalculation of lung volumes in the BTPS system are performed automatically.

Interpretation of results

A practitioner should have a good idea of ​​the true possibilities of the spirographic research method, which are usually limited by the lack of information about the values ​​of the residual lung volume (RLV), functional residual capacity (FRC) and total lung capacity (TLC), which does not allow a full analysis of the RL structure. At the same time, spirography makes it possible to get a general idea of ​​the state of external respiration, in particular:

1. identify a decrease in lung capacity (VC);
2. identify violations of tracheobronchial patency, and using modern computer analysis of the flow-volume loop - at the earliest stages of the development of obstructive syndrome;
3. identify the presence of restrictive disorders of pulmonary ventilation in cases where they are not combined with impaired bronchial patency.

Modern computer spirography allows obtaining reliable and complete information about the presence of broncho-obstructive syndrome. More or less reliable detection of restrictive ventilation disorders using the spirographic method (without the use of gas-analytical methods for assessing the structure of the TEL) is possible only in relatively simple, classic cases of impaired lung compliance, when they are not combined with impaired bronchial patency.

Diagnosis of obstructive syndrome

The main spirographic sign of obstructive syndrome is the slowing down of forced exhalation due to an increase in airway resistance. When registering a classic spirogram, the forced expiratory curve becomes stretched, such indicators as FEV1 and the Tiffno index (FEV1 / FVC, or FEV, / FVC) decrease. VC (VC) at the same time either does not change, or slightly decreases.

A more reliable sign of broncho-obstructive syndrome is a decrease in the Tiffno index (FEV1 / FVC, or FEV1 / FVC), since the absolute value of FEV1 (FEV1) can decrease not only with bronchial obstruction, but also with restrictive disorders due to a proportional decrease in all lung volumes and capacities, including FEV1 (FEV1) and FVC (FVC).

Already in the early stages of the development of an obstructive syndrome, the calculated indicator of the average volumetric velocity decreases at the level of 25-75% of FVC (SOS25-75%) - O "is the most sensitive spirographic indicator, indicating an increase in airway resistance earlier than others. However, its calculation requires sufficient accurate manual measurements of the descending knee of the FVC curve, which is not always possible according to the classical spirogram.

More accurate and more accurate data can be obtained by analyzing the flow-volume loop using modern computerized spirographic systems. Obstructive disorders are accompanied by changes predominantly in the expiratory part of the flow-volume loop. If in most healthy people this part of the loop resembles a triangle with an almost linear decrease in the volumetric air flow rate during exhalation, then in patients with impaired bronchial patency, a kind of “sagging” of the expiratory part of the loop and a decrease in the volumetric air flow rate are observed at all values ​​of lung volume. Often, due to an increase in lung volume, the expiratory part of the loop is shifted to the left.

Reduced spirographic indicators such as FEV1 (FEV1), FEV1 / FVC (FEV1 / FVC), peak expiratory volume flow rate (POS vyd, or PEF), MOS25% (MEF25), MOS50% (MEF50), MOC75% (MEF75) and COC25-75% (FEF25-75).

Vital capacity (VC) may remain unchanged or decrease even in the absence of concomitant restrictive disorders. At the same time, it is also important to assess the value of the expiratory reserve volume (ERV), which naturally decreases in obstructive syndrome, especially when early expiratory closure (collapse) of the bronchi occurs.

According to some researchers, a quantitative analysis of the expiratory part of the flow-volume loop also makes it possible to get an idea of ​​the predominant narrowing of large or small bronchi. It is believed that obstruction of the large bronchi is characterized by a decrease in forced expiratory volume velocity, mainly in the initial part of the loop, and therefore such indicators as peak volume velocity (PFR) and maximum volume velocity at the level of 25% of FVC (MOV25%) are sharply reduced or MEF25). At the same time, the volume flow rate of air in the middle and end of expiration (MOC50% and MOC75%) also decreases, but to a lesser extent than POS vyd and MOS25%. On the contrary, with obstruction of small bronchi, a decrease in MOC50% is predominantly detected. MOS75%, while MOSvyd is normal or slightly reduced, and MOS25% is moderately reduced.

However, it should be emphasized that these provisions are currently quite controversial and cannot be recommended for use in general clinical practice. In any case, there are more reasons to believe that the uneven decrease in the volumetric air flow rate during forced expiration reflects the degree of bronchial obstruction rather than its localization. early stages bronchial constriction is accompanied by a slowdown in the expiratory air flow at the end and middle of expiration (decrease in MOS50%, MOS75%, SOS25-75% with little-changed values ​​of MOS25%, FEV1/FVC and POS), whereas with severe bronchial obstruction, a relatively proportional decrease in all speed indicators is observed , including the Tiffno index (FEV1/FVC), POS and MOS25%.

Of interest is the diagnosis of obstruction of the upper airways (larynx, trachea) using computer spirographs. There are three types of such obstruction:

1. fixed obstruction;
2. variable extrathoracic obstruction;
3. variable intrathoracic obstruction.

An example of a fixed obstruction of the upper airways is deer stenosis due to the presence of a tracheostomy. In these cases, breathing is carried out through a rigid, relatively narrow tube, the lumen of which does not change during inhalation and exhalation. This fixed obstruction limits the flow of air both inspiratory and expiratory. Therefore, the expiratory part of the curve resembles the inspiratory part in shape; volumetric inspiratory and expiratory velocities are significantly reduced and almost equal to each other.

In the clinic, however, more often one has to deal with two variants of variable obstruction of the upper airways, when the lumen of the larynx or trachea changes the time of inhalation or exhalation, which leads to selective limitation of inspiratory or expiratory air flows, respectively.

Variable extrathoracic obstruction is observed with various kinds of stenosis of the larynx (edema of the vocal cords, swelling, etc.). As is known, during respiratory movements, the lumen of the extrathoracic airways, especially narrowed ones, depends on the ratio of intratracheal and atmospheric pressures. During inspiration, the pressure in the trachea (as well as the intraalveolar and intrapleural pressure) becomes negative, i.e. below atmospheric. This contributes to the narrowing of the lumen of the extrathoracic airways and a significant limitation of the inspiratory air flow and a decrease (flattening) of the inspiratory part of the flow-volume loop. During forced exhalation, intratracheal pressure becomes significantly higher than atmospheric pressure, and therefore the diameter of the airways approaches normal, and the expiratory part of the flow-volume loop changes little. Variable intrathoracic obstruction of the upper airways is also observed in tumors of the trachea and dyskinesia of the membranous part of the trachea. The diameter of the thoracic airways is largely determined by the ratio of intratracheal and intrapleural pressures. With forced exhalation, when intrapleural pressure increases significantly, exceeding the pressure in the trachea, the intrathoracic airways narrow, and their obstruction develops. During inspiration, the pressure in the trachea slightly exceeds the negative intrapleural pressure, and the degree of narrowing of the trachea decreases.

Thus, with variable intrathoracic obstruction of the upper airways, there is a selective limitation of the air flow on exhalation and flattening of the inspiratory part of the loop. Its inspiratory part remains almost unchanged.

With variable extrathoracic obstruction of the upper airways, selective restriction of the volumetric airflow rate is observed mainly on inspiration, with intrathoracic obstruction - on expiration.

It should also be noted that in clinical practice, cases are quite rare when the narrowing of the lumen of the upper airways is accompanied by flattening of only the inspiratory or only the expiratory part of the loop. Usually reveals airflow limitation in both phases of breathing, although during one of them this process is much more pronounced.

Diagnosis of restrictive disorders

Restrictive violations of pulmonary ventilation are accompanied by a limitation of filling the lungs with air due to a decrease in the respiratory surface of the lung, turning off part of the lung from breathing, reducing the elastic properties of the lung and chest, as well as the ability of the lung tissue to stretch (inflammatory or hemodynamic pulmonary edema, massive pneumonia, pneumoconiosis, pneumosclerosis and so-called). At the same time, if restrictive disorders are not combined with the violations of bronchial patency described above, airway resistance usually does not increase.

The main consequence of restrictive (restrictive) ventilation disorders detected by classical spirography is an almost proportional decrease in most lung volumes and capacities: TO, VC, RO ind, RO vy, FEV, FEV1, etc. It is important that, unlike the obstructive syndrome, a decrease in FEV1 is not accompanied by a decrease in the FEV1/FVC ratio. This indicator remains within the normal range or even slightly increases due to a more significant decrease in VC.

In computed spirography, the flow-volume curve is a reduced copy of the normal curve, shifted to the right due to a general decrease in lung volume. Peak volumetric flow rate (PFR) of expiratory flow FEV1 is reduced, although the FEV1/FVC ratio is normal or increased. Due to the limitation of lung expansion and, accordingly, a decrease in its elastic traction, flow rates (for example, COC25-75%, MOC50%, MOC75%) in some cases can also be reduced even in the absence of airway obstruction.

The most important diagnostic criteria restrictive ventilation disorders that can be reliably distinguished from obstructive disorders are:

1. an almost proportional decrease in lung volumes and capacities measured by spirography, as well as flow indicators and, accordingly, a normal or slightly changed shape of the curve of the flow-volume loop, shifted to the right;
2. normal or even increased value of the Tiffno index (FEV1 / FVC);
3. the decrease in inspiratory reserve volume (RIV) is almost proportional to the expiratory reserve volume (ROV).

It should be emphasized once again that for the diagnosis of even “pure” restrictive ventilation disorders, one cannot focus only on a decrease in VC, since the sweat rate in severe obstructive syndrome can also decrease significantly. More reliable differential diagnostic signs are the absence of changes in the shape of the expiratory part of the flow-volume curve (in particular, normal or increased values ​​of FB1 / FVC), as well as a proportional decrease in RO ind and RO vy.

Determination of the structure of total lung capacity (TLC, or TLC)

As mentioned above, the methods of classical spirography, as well as computer processing of the flow-volume curve, make it possible to get an idea of ​​​​the changes in only five of the eight lung volumes and capacities (TO, RVD, ROV, VC, EVD, or, respectively - VT, IRV, ERV , VC and 1C), which makes it possible to assess predominantly the degree of obstructive pulmonary ventilation disorders. Restrictive disorders can be reliably diagnosed only if they are not combined with a violation of bronchial patency, i.e. in the absence of mixed disorders of pulmonary ventilation. Nevertheless, in the practice of a doctor, such mixed disorders are most often encountered (for example, in chronic obstructive bronchitis or bronchial asthma, complicated by emphysema and pneumosclerosis, etc.). In these cases, the mechanisms of impaired pulmonary ventilation can only be identified by analyzing the structure of the RFE.

To solve this problem, you need to use additional methods determine functional residual capacity (FRC, or FRC) and calculate indicators of residual lung volume (ROL, or RV) and total lung capacity (TLC, or TLC). Since FRC is the amount of air remaining in the lungs after maximum expiration, it is measured only by indirect methods (gas analysis or using whole body plethysmography).

The principle of gas analysis methods is that the lungs are either injected with an inert gas helium (dilution method), or the nitrogen contained in the alveolar air is washed out, forcing the patient to breathe pure oxygen. In both cases, the FRC is calculated from the final gas concentration (R.F. Schmidt, G. Thews).

Helium dilution method. Helium, as is known, is an inert and harmless gas for the body, which practically does not pass through the alveolar-capillary membrane and does not participate in gas exchange.

The dilution method is based on measuring the helium concentration in the closed container of the spirometer before and after mixing the gas with the lung volume. A covered spirometer with a known volume (V cn) is filled with a gas mixture consisting of oxygen and helium. At the same time, the volume occupied by helium (V cn) and its initial concentration (FHe1) are also known. After a quiet exhalation, the patient begins to breathe from the spirometer, and helium is evenly distributed between the volume of the lungs (FOE, or FRC) and the volume of the spirometer (V cn). After a few minutes, the helium concentration in the general system (“spirometer-lungs”) decreases (FHe 2).

Nitrogen washout method. In this method, the spirometer is filled with oxygen. The patient breathes into the closed circuit of the spirometer for several minutes, while measuring the volume of exhaled air (gas), the initial content of nitrogen in the lungs and its final content in the spirometer. The FRC (FRC) is calculated using an equation similar to that of the helium dilution method.

The accuracy of both of the above methods for determining the FRC (RR) depends on the completeness of the mixing of gases in the lungs, which in healthy people occurs within a few minutes. However, in some diseases accompanied by a pronounced uneven ventilation (for example, with obstructive pulmonary pathology), balancing the concentration of gases takes long time. In these cases, the measurement of FRC (FRC) by the methods described may be inaccurate. These shortcomings are devoid of the more technically complex method of whole body plethysmography.

Whole body plethysmography. The method of whole body plethysmography is one of the most informative and complex research methods used in pulmonology to determine lung volumes, tracheobronchial resistance, elastic properties of lung tissue and chest, as well as to evaluate some other parameters of pulmonary ventilation.

The integral plethysmograph is a hermetically sealed chamber with a volume of 800 liters, in which the patient is freely placed. The subject breathes through a pneumotachograph tube connected to a hose open to the atmosphere. The hose has a flap that allows you to automatically shut off the air flow at the right time. Special barometric sensors measure the pressure in the chamber (Pcam) and in oral cavity(Rrot). the latter, with the valve of the hose closed, is equal to the alveolar pressure inside. The pneumotachograph allows you to determine the air flow (V).

The principle of operation of an integral plethysmograph is based on Boyle Moriosht's law, according to which, at a constant temperature, the relationship between pressure (P) and gas volume (V) remains constant:

P1xV1 = P2xV2, where P1 is the initial gas pressure, V1 is the initial gas volume, P2 is the pressure after changing the gas volume, V2 is the volume after changing the gas pressure.

The patient inside the plethysmograph chamber inhales and exhales calmly, after which (at the FRC level, or FRC) the hose flap is closed, and the subject makes an attempt to “inhale” and “exhale” (the “breathing” maneuver) With this “breathing” maneuver intra-alveolar pressure changes, and the pressure in the closed chamber of the plethysmograph changes inversely proportional to it. When you try to "inhale" with a closed valve, the volume of the chest increases, which leads, on the one hand, to a decrease in intra-alveolar pressure, and on the other hand, to a corresponding increase in pressure in the plethysmograph chamber (Pcam). On the contrary, when you try to "exhale" the alveolar pressure increases, and the volume of the chest and the pressure in the chamber decrease.

Thus, the whole body plethysmography method makes it possible to calculate intrathoracic gas volume (IGO) with high accuracy, which in healthy individuals quite accurately corresponds to the value of functional residual lung capacity (FRC, or CS); the difference between VGO and FOB usually does not exceed 200 ml. However, it should be remembered that in case of impaired bronchial patency and some other pathological conditions, VGO can significantly exceed the value of the true FOB due to an increase in the number of unventilated and poorly ventilated alveoli. In these cases, it is advisable to combine a study using gas analytical methods of the whole body plethysmography method. By the way, the difference between VOG and FOB is one of the important indicators of uneven ventilation of the lungs.

Interpretation of results

The main criterion for the presence of restrictive disorders of pulmonary ventilation is a significant decrease in the TEL. With a "pure" restriction (without a combination of bronchial obstruction), the structure of the TEL does not change significantly, or a slight decrease in the ratio of TOL/TEL was observed. If restrictive disorders occur against the background of bronchial patency disorders (mixed type of ventilation disorders), along with a clear decrease in the TFR, a significant change in its structure is observed, which is characteristic of broncho-obstructive syndrome: an increase in TRL/TRL (more than 35%) and FFU/TEL (more than 50% ). In both variants of restrictive disorders, VC is significantly reduced.

Thus, the analysis of the structure of the REL makes it possible to differentiate all three variants of ventilation disorders (obstructive, restrictive, and mixed), while the assessment of only spirographic parameters does not make it possible to reliably distinguish the mixed variant from the obstructive variant, accompanied by a decrease in VC).

The main criterion for the obstructive syndrome is a change in the structure of the REL, in particular, an increase in the ROL / TEL (more than 35%) and FFU / TEL (more than 50%). For “pure” restrictive disorders (without a combination with obstruction), the most characteristic is a decrease in the TEL without changing its structure. The mixed type of ventilation disturbances is characterized by a significant decrease in the TRL and an increase in the ratios of TOL/TEL and FFU/TEL.

Determination of uneven ventilation of the lungs

In a healthy person, there is a certain physiological uneven ventilation of different parts of the lungs, due to differences in the mechanical properties of the airways and lung tissue, as well as the presence of the so-called vertical pleural pressure gradient. If the patient is in an upright position, at the end of exhalation, pleural pressure in the upper lung is more negative than in the lower (basal) sections. The difference can reach 8 cm of water column. Therefore, before the start of the next breath, the alveoli of the tops of the lungs are stretched more than the alveoli of the lower basal regions. In this regard, during inspiration, a larger volume of air enters the alveoli of the basal regions.

The alveoli of the lower basal sections of the lungs are normally better ventilated than the areas of the apexes, which is associated with the presence of a vertical intrapleural pressure gradient. However, normally, such uneven ventilation is not accompanied by a noticeable disturbance of gas exchange, since the blood flow in the lungs is also uneven: the basal sections are better perfused than the apical ones.

In some diseases of the respiratory system, the degree of uneven ventilation can increase significantly. The most common causes of such pathological uneven ventilation are:

• Diseases accompanied by an uneven increase in airway resistance (chronic bronchitis, bronchial asthma).
• Diseases with unequal regional extensibility of lung tissue (pulmonary emphysema, pneumosclerosis).
• Inflammation of the lung tissue (focal pneumonia).
• Diseases and syndromes, combined with local restriction of expansion of the alveoli (restrictive) - exudative pleurisy, hydrothorax, pneumosclerosis, etc.

Often various reasons are combined. For example, in chronic obstructive bronchitis complicated by emphysema and pneumosclerosis, regional disorders of bronchial patency and extensibility of the lung tissue develop.

With uneven ventilation, the physiological dead space increases significantly, gas exchange in which does not occur or is weakened. This is one of the reasons for the development of respiratory failure.

To assess the unevenness of pulmonary ventilation, gas analytical and barometric methods are more often used. Thus, a general idea of ​​the uneven ventilation of the lungs can be obtained, for example, by analyzing the curves of helium mixing (dilution) or nitrogen leaching, which are used to measure FRC.

In healthy people, mixing helium with alveolar air or washing out nitrogen from it occurs within three minutes. With violations of bronchial patency, the number (volume) of poorly ventilated alveoli increases dramatically, and therefore the mixing (or washing out) time increases significantly (up to 10-15 minutes), which is an indicator of uneven pulmonary ventilation.

More accurate data can be obtained using a nitrogen leaching test with a single breath of oxygen. The patient exhales as much as possible, and then inhales pure oxygen as deeply as possible. Then he exhales slowly closed system spirograph equipped with a device for determining the concentration of nitrogen (azotograph). Throughout the exhalation, the volume of the exhaled gas mixture is continuously measured, and the changing concentration of nitrogen in the exhaled gas mixture containing nitrogen of the alveolar air is also determined.

The nitrogen leaching curve consists of 4 phases. At the very beginning of exhalation, air enters the spirograph from the upper airways, which is 100% p. oxygen that filled them during the previous breath. The nitrogen content in this portion of exhaled gas is zero.

The second phase is characterized by a sharp increase in the concentration of nitrogen, which is due to the leaching of this gas from the anatomical dead space.

During the long third phase, the nitrogen concentration of the alveolar air is recorded. In healthy people, this phase of the curve is flat - in the form of a plateau (alveolar plateau). If there is uneven ventilation during this phase, the nitrogen concentration increases due to the gas being washed out from the poorly ventilated alveoli, which are emptied last. Thus, the greater the rise in the nitrogen washout curve at the end of the third phase, the more pronounced is the unevenness of pulmonary ventilation.

The fourth phase of the nitrogen washout curve is associated with the expiratory closure of the small airways of the basal parts of the lungs and the inflow of air mainly from the apical parts of the lungs, the alveolar air in which contains nitrogen of a higher concentration.

Assessment of the ventilation-perfusion ratio

Gas exchange in the lungs depends not only on the level of general ventilation and the degree of its unevenness in various parts of the organ, but also on the ratio of ventilation and perfusion at the level of the alveoli. Therefore, the value of the ventilation-perfusion ratio (VPO) is one of the most important functional characteristics of the respiratory organs, which ultimately determines the level of gas exchange.

Normal VPO for the lung as a whole is 0.8-1.0. With a decrease in VPO below 1.0, perfusion of poorly ventilated areas of the lungs leads to hypoxemia (decrease in oxygenation arterial blood). An increase in VPO greater than 1.0 is observed with preserved or excessive ventilation of zones, the perfusion of which is significantly reduced, which can lead to impaired CO2 excretion - hypercapnia.

Causes of HPE violation:

1. All diseases and syndromes that cause uneven ventilation of the lungs.
2. The presence of anatomical and physiological shunts.
3. Thromboembolism of small branches of the pulmonary artery.
4. Violation of microcirculation and thrombosis in the vessels of the small circle.

Capnography. Several methods have been proposed to detect violations of HPV, of which one of the simplest and most accessible is the capnography method. It is based on the continuous registration of CO2 content in the exhaled mixture of gases using special gas analyzers. These instruments measure the absorption of infrared rays by carbon dioxide as it passes through an exhaled gas cuvette.

When analyzing a capnogram, three indicators are usually calculated:

1. slope of the alveolar phase of the curve (segment BC),
2. the value of CO2 concentration at the end of exhalation (at point C),
3. the ratio of functional dead space (MP) to tidal volume (TO) - MP / DO.

Determination of diffusion of gases

Diffusion of gases through the alveolar-capillary membrane obeys Fick's law, according to which the diffusion rate is directly proportional to:

1. partial pressure gradient of gases (O2 and CO2) on both sides of the membrane (P1 - P2) and
2. diffusion capacity of the alveolar-caillary membrane (Dm):

VG \u003d Dm x (P1 - P2), where VG is the gas transfer rate (C) through the alveolar-capillary membrane, Dm is the diffusion capacity of the membrane, P1 - P2 is the partial pressure gradient of gases on both sides of the membrane.

To calculate the diffusion capacity of light POs for oxygen, it is necessary to measure the 62 (VO 2 ) uptake and the average O 2 partial pressure gradient. VO 2 values ​​are measured using an open or closed type spirograph. To determine the oxygen partial pressure gradient (P 1 - P 2), more complex gas analytical methods are used, since in clinical conditions it is difficult to measure the partial pressure of O 2 in the pulmonary capillaries.

The most commonly used definition of the diffusion capacity of light is ne for O 2, but for carbon monoxide (CO). Since CO binds 200 times more actively with hemoglobin than oxygen, its concentration in the blood of the pulmonary capillaries can be neglected. Then, to determine DlCO, it is sufficient to measure the rate of passage of CO through the alveolar-capillary membrane and the gas pressure in the alveolar air.

The single-breath method is most widely used in the clinic. The subject inhales a gas mixture with a small content of CO and helium, and at the height of a deep breath for 10 seconds holds his breath. After that, the composition of the exhaled gas is determined by measuring the concentration of CO and helium, and the diffusion capacity of the lungs for CO is calculated.

Normally, DlCO, reduced to body area, is 18 ml/min/mm Hg. st./m2. The diffusion capacity of the lungs for oxygen (DlO2) is calculated by multiplying DlCO by a factor of 1.23.

The following diseases most often cause a decrease in the diffusion capacity of the lungs.

• Emphysema of the lungs (due to a decrease in the surface area of ​​the alveolar-capillary contact and the volume of capillary blood).
• Diseases and syndromes accompanied by diffuse lesions of the lung parenchyma and thickening of the alveolar-capillary membrane (massive pneumonia, inflammatory or hemodynamic pulmonary edema, diffuse pneumosclerosis, alveolitis, pneumoconiosis, cystic fibrosis, etc.).
• Diseases accompanied by damage to the capillary bed of the lungs (vasculitis, embolism of small branches of the pulmonary artery, etc.).

For the correct interpretation of changes in the diffusion capacity of the lungs, it is necessary to take into account the hematocrit index. An increase in hematocrit in polycythemia and secondary erythrocytosis is accompanied by an increase, and its decrease in anemia is accompanied by a decrease in the diffusion capacity of the lungs.

Airway resistance measurement

Measurement of airway resistance is a diagnostically important parameter of pulmonary ventilation. Aspirated air moves through the airways under the action of a pressure gradient between the oral cavity and the alveoli. During inspiration, expansion of the chest leads to a decrease in viutripleural and, accordingly, intra-alveolar pressure, which becomes lower than the pressure in the oral cavity (atmospheric). As a result, the air flow is directed into the lungs. During expiration, the action of the elastic recoil of the lungs and chest is aimed at increasing the intra-alveolar pressure, which becomes higher than the pressure in the oral cavity, resulting in a reverse flow of air. Thus, the pressure gradient (∆P) is the main force that ensures the transport of air through the airways.

The second factor that determines the amount of gas flow through the airways is the aerodynamic drag (Raw), which, in turn, depends on the clearance and length of the airways, as well as on the viscosity of the gas.

The value of the volumetric air flow rate obeys the Poiseuille law: V = ∆P / Raw, where

• V is the volumetric velocity of the laminar air flow;
• ∆P - pressure gradient in the oral cavity and alveoli;
• Raw - aerodynamic resistance of the airways.

It follows that in order to calculate the aerodynamic resistance of the airways, it is necessary to simultaneously measure the difference between the pressure in the oral cavity in the alveoli (∆P), as well as the volumetric air flow rate.

There are several methods for determining Raw based on this principle:

• whole body plethysmography method;
• airflow blocking method.

Determination of blood gases and acid-base status

The main method for diagnosing acute respiratory failure is the study of arterial blood gases, which includes the measurement of PaO2, PaCO2 and pH. You can also measure the saturation of hemoglobin with oxygen (oxygen saturation) and some other parameters, in particular the content of buffer bases (BB), standard bicarbonate (SB) and the amount of excess (deficit) of bases (BE).

The parameters PaO2 and PaCO2 most accurately characterize the ability of the lungs to saturate the blood with oxygen (oxygenation) and remove carbon dioxide (ventilation). The latter function is also determined from the pH and BE values.

To determine the gas composition of the blood in patients with acute respiratory failure in intensive care units, a complex invasive technique for obtaining arterial blood is used by puncturing a large artery. More often, a puncture of the radial artery is performed, since the risk of developing complications is lower. The hand has a good collateral blood flow, which is carried out by the ulnar artery. Therefore, even if the radial artery is damaged during puncture or operation of the arterial catheter, the blood supply to the hand is preserved.

Indications for puncture of the radial artery and placement of an arterial catheter are:

• the need for frequent measurement of arterial blood gases;
• severe hemodynamic instability against the background of acute respiratory failure and the need for constant monitoring of hemodynamic parameters.

Catheter insertion is contraindicated negative test Allen. For the test, the ulnar and radial arteries are pinched with fingers so as to turn the arterial blood flow; the hand turns pale after a while. After that, the ulnar artery is released, continuing to compress the radial. Usually the color of the brush is quickly (within 5 seconds) restored. If this does not happen, then the hand remains pale, ulnar artery occlusion is diagnosed, the test result is considered negative, and the radial artery is not punctured.

When positive result test palm and forearm of the patient is fixed. After preparing the surgical field in the distal parts of the radial artery, the guests palpate the pulse on the radial artery, perform anesthesia in this place, and puncture the artery at an angle of 45°. The catheter is advanced until blood appears in the needle. The needle is removed, leaving the catheter in the artery. To prevent excessive bleeding, the proximal part of the radial artery is pressed with a finger for 5 minutes. The catheter is fixed to the skin with silk sutures and covered with a sterile dressing.

Complications (bleeding, arterial occlusion by a thrombus, and infection) during catheter placement are relatively rare.

It is preferable to draw blood for research into a glass rather than a plastic syringe. It is important that the blood sample does not come into contact with the surrounding air, i.e. collection and transport of blood should be carried out under anaerobic conditions. Otherwise, exposure to the blood sample of ambient air leads to the determination of the level of PaO2.

Determination of blood gases should be carried out no later than 10 minutes after arterial blood sampling. Otherwise, ongoing metabolic processes in the blood sample (initiated mainly by the activity of leukocytes) significantly change the results of the determination of blood gases, reducing the level of PaO2 and pH, and increasing PaCO2. Especially pronounced changes are observed in leukemia and in severe leukocytosis.

Methods for assessing the acid-base state

Measurement of blood pH

The pH value of blood plasma can be determined by two methods:

• The indicator method is based on the property of some weak acids or bases, used as indicators, to dissociate at certain pH values, thus changing the color.
• The pH-metry method makes it possible to more accurately and quickly determine the concentration of hydrogen ions using special polarographic electrodes, on the surface of which, when immersed in a solution, a potential difference is created that depends on the pH of the medium under study.

One of the electrodes - active, or measuring, is made of a noble metal (platinum or gold). The other (reference) serves as a reference electrode. The platinum electrode is separated from the rest of the system by a glass membrane permeable only to hydrogen ions (H+). Inside the electrode is filled with a buffer solution.

The electrodes are immersed in the test solution (for example, blood) and polarized from a current source. As a result, a current appears in a closed electrical circuit. Since the platinum (active) electrode is additionally separated from the electrolyte solution by a glass membrane permeable only to H + ions, the pressure on both surfaces of this membrane is proportional to blood pH.

Most often, the acid-base state is assessed by the Astrup method on the microAstrup apparatus. Determine the indicators of BB, BE and PaCO2. Two portions of the studied arterial blood are brought into equilibrium with two gas mixtures of known composition, differing in the partial pressure of CO2. pH is measured in each portion of blood. The pH and PaCO2 values ​​in each portion of blood are plotted as two points on a nomogram. Through 2 points marked on the nomogram, a straight line is drawn to the intersection with the standard graphs of BB and BE and the actual values ​​of these indicators are determined. Then measure the pH of the blood under study and find on the resulting straight point corresponding to this measured pH value. The projection of this point onto the y-axis determines the actual pressure of CO2 in the blood (PaCO2).

Direct measurement of CO2 pressure (PaCO2)

In recent years, for direct measurement of PaCO2 in a small volume, a modification of polarographic electrodes designed to measure pH has been used. Both electrodes (active and reference) are immersed in an electrolyte solution, which is separated from the blood by another membrane, permeable only to gases, but not to hydrogen ions. CO2 molecules, diffusing through this membrane from the blood, change the pH of the solution. As mentioned above, the active electrode is additionally separated from the NaHCO3 solution by a glass membrane permeable only to H + ions. After the electrodes are immersed in the test solution (for example, blood), the pressure on both surfaces of this membrane is proportional to the pH of the electrolyte (NaHCO3). In turn, the pH of the NaHCO3 solution depends on the concentration of CO2 in the blood. Thus, the magnitude of the pressure in the circuit is proportional to the PaCO2 of the blood.

The polarographic method is also used to determine PaO2 in arterial blood.

Determination of BE from the results of direct measurement of pH and PaCO2

Direct determination of pH and PaCO2 of the blood makes it possible to significantly simplify the procedure for determining the third indicator of the acid-base state - the excess of bases (BE). The latter indicator can be determined by special nomograms. After direct measurement of pH and PaCO2, the actual values ​​of these indicators are plotted on the corresponding nomogram scales. The points are connected by a straight line and continue it until it intersects with the BE scale.

This method of determining the main indicators of the acid-base state does not require balancing the blood with a gas mixture, as when using the classical Astrup method.

Interpretation of results

Partial pressure of O2 and CO2 in arterial blood

The values ​​of PaO2 and PaCO2 serve as the main objective indicators of respiratory failure. In a healthy adult breathing room air with an oxygen concentration of 21% (FiO 2 \u003d 0.21) and normal atmospheric pressure (760 mm Hg), PaO 2 is 90-95 mm Hg. Art. With a change in barometric pressure, ambient temperature and some other conditions, PaO2 in a healthy person can reach 80 mm Hg. Art.

Lower values ​​of PaO2 (less than 80 mm Hg) can be considered the initial manifestation of hypoxemia, especially against the background of acute or chronic damage to the lungs, chest, respiratory muscles, or the central regulation of respiration. Reducing PaO2 to 70 mm Hg. Art. in most cases indicates compensated respiratory failure and is usually accompanied by clinical signs decrease in the functionality of the external respiration system:

• slight tachycardia;
• shortness of breath, respiratory discomfort, appearing mainly during physical exertion, although at rest the respiratory rate does not exceed 20-22 per minute;
• a noticeable decrease in exercise tolerance;
• participation in breathing of the auxiliary respiratory muscles, etc.

At first glance, these criteria for arterial hypoxemia contradict the definition of respiratory failure by E. Campbell: “respiratory failure is characterized by a decrease in PaO2 below 60 mm Hg. st ... ". However, as already noted, this definition refers to decompensated respiratory failure, manifested by a large number of clinical and instrumental signs. Indeed, a decrease in PaO2 below 60 mm Hg. Art., as a rule, indicates severe decompensated respiratory failure, and is accompanied by shortness of breath at rest, an increase in the number of respiratory movements up to 24-30 per minute, cyanosis, tachycardia, significant pressure of the respiratory muscles, etc. Neurological disorders and signs of hypoxia in other organs usually develop when PaO2 is below 40-45 mm Hg. Art.

PaO2 from 80 to 61 mm Hg. Art., especially against the background of acute or chronic damage to the lungs and the respiratory apparatus, should be regarded as the initial manifestation of arterial hypoxemia. In most cases, it indicates the formation of mild compensated respiratory failure. Reducing PaO 2 below 60 mm Hg. Art. indicates moderate or severe precompensated respiratory failure, clinical manifestations which are clearly expressed.

Normally, the pressure of CO2 in arterial blood (PaCO 2) is 35-45 mm Hg. Hypercapia is diagnosed when PaCO2 rises above 45 mm Hg. Art. PaCO2 values ​​are greater than 50 mm Hg. Art. usually correspond to the clinical picture of severe ventilation (or mixed) respiratory failure, and above 60 mm Hg. Art. - serve as an indication for mechanical ventilation, aimed at restoring the minute volume of breathing.

Diagnostics various forms respiratory failure (ventilation, parenchymal, etc.) is based on the results of a comprehensive examination of patients - the clinical picture of the disease, the results of determining the function of external respiration, chest X-ray, laboratory tests, including the assessment of blood gas composition.

Above, some features of the change in PaO 2 and PaCO 2 in ventilation and parenchymal respiratory failure have already been noted. Recall that for ventilation respiratory failure, in which the process of releasing CO 2 from the body is disturbed in the lungs, hypercapnia is characteristic (PaCO 2 is more than 45-50 mm Hg), often accompanied by compensated or decompensated respiratory acidosis. At the same time, progressive hypoventilation of the alveoli naturally leads to a decrease in the oxygenation of the alveolar air and the pressure of O 2 in arterial blood (PaO 2), resulting in the development of hypoxemia. Thus, a detailed picture of ventilation respiratory failure is accompanied by both hypercapnia and increasing hypoxemia.

The early stages of parenchymal respiratory failure are characterized by a decrease in PaO 2 (hypoxemia), in most cases combined with severe hyperventilation of the alveoli (tachypnea) and developing in connection with this hypocapnia and respiratory alkalosis. If this condition cannot be stopped, signs of a progressive total decrease in ventilation, minute respiratory volume and hypercapnia gradually appear (PaCO 2 is more than 45-50 mm Hg). This indicates the accession of ventilation respiratory failure due to fatigue of the respiratory muscles, a pronounced obstruction of the airways, or a critical drop in the volume of functioning alveoli. Thus, the later stages of parenchymal respiratory failure are characterized by a progressive decrease in PaO 2 (hypoxemia) in combination with hypercapnia.

Depending on the individual features development of the disease and the predominance of certain pathophysiological mechanisms of respiratory failure, other combinations of hypoxemia and hypercapnia are possible, which are discussed in subsequent chapters.

Acid-base disorders

In most cases, to accurately diagnose respiratory and non-respiratory acidosis and alkalosis, as well as to assess the degree of compensation for these disorders, it is quite sufficient to determine blood pH, pCO2, BE, and SB.

During the period of decompensation, a decrease in blood pH is observed, and in alkalosis, it is quite simple to determine the values ​​of the acid-base state: with acidego, an increase. It is also easy to determine the respiratory and non-respiratory types of these disorders by laboratory parameters: changes in pCO 2 and BE in each of these two types are multidirectional.

The situation is more complicated with the assessment of the parameters of the acid-base state during the period of compensation for its violations, when the pH of the blood is not changed. Thus, a decrease in pCO 2 and BE can be observed both in non-respiratory (metabolic) acidosis and in respiratory alkalosis. In these cases, an assessment of the overall clinical situation helps to understand whether the corresponding changes in pCO 2 or BE are primary or secondary (compensatory).

Compensated respiratory alkalosis is characterized by a primary increase in PaCO2, which is essentially the cause of this acid-base disorder; in these cases, the corresponding changes in BE are secondary, that is, they reflect the inclusion of various compensatory mechanisms aimed at reducing the concentration of bases. On the contrary, for compensated metabolic acidosis, changes in BE are primary, and shifts in pCO2 reflect compensatory hyperventilation of the lungs (if it is possible).

Thus, comparing the parameters of acid-base disturbances with clinical picture diseases in most cases allows to reliably diagnose the nature of these disorders even in the period of their compensation. Establishing the correct diagnosis in these cases can also help evaluate changes in the electrolyte composition of the blood. In respiratory and metabolic acidosis, hypernatremia (or normal concentration of Na +) and hyperkalemia are often observed, and in respiratory alkalosis, hypo- (or normo) natremia and hypokalemia

Pulse oximetry

The supply of oxygen to peripheral organs and tissues depends not only on the absolute values ​​of D2 pressure in arterial blood, but also on the ability of hemoglobin to bind oxygen in the lungs and release it in the tissues. This ability is described by an S-shaped oxyhemoglobin dissociation curve. The biological meaning of this shape of the dissociation curve is that the region of high values ​​of O2 pressure corresponds to the horizontal section of this curve. Therefore, even with fluctuations in oxygen pressure in arterial blood from 95 to 60-70 mm Hg. Art. saturation (saturation) of hemoglobin with oxygen (SaO 2) remains at a sufficiently high level. Yes, healthy young man at PaO 2 \u003d 95 mm Hg. Art. saturation of hemoglobin with oxygen is 97%, and at PaO 2 = 60 mm Hg. Art. - 90%. The steep slope of the middle section of the oxyhemoglobin dissociation curve indicates a very favorable conditions to provide oxygen to the tissues.

Under the influence of certain factors (temperature increase, hypercapnia, acidosis), the dissociation curve shifts to the right, which indicates a decrease in the affinity of hemoglobin for oxygen and the possibility of its easier release in tissues. the same level requires more PaO 2 .

The shift of the oxyhemoglobin dissociation curve to the left indicates an increased affinity of hemoglobin for O 2 and its lower release in tissues. Such a shift occurs due to the action of hypocapnia, alkalosis and more. low temperatures. In these cases, a high saturation of hemoglobin with oxygen is maintained even at lower values ​​of PaO 2

Thus, the value of saturation of hemoglobin with oxygen in respiratory failure acquires an independent value for characterizing the provision of peripheral tissues with oxygen. The most common non-invasive method for determining this indicator is pulse oximetry.

Modern pulse oximeters contain a microprocessor connected to a sensor containing a light emitting diode and a light sensitive sensor located opposite the light emitting diode). Usually 2 wavelengths of radiation are used: 660 nm (red light) and 940 nm (infrared). Oxygen saturation is determined by the absorption of red and infrared light, respectively, by reduced hemoglobin (Hb) and oxyhemoglobin (HbJ 2 ). The result is displayed as SaO2 (saturation obtained from pulse oximetry).

Normal oxygen saturation is over 90%. This indicator decreases with hypoxemia and a decrease in PaO 2 less than 60 mm Hg. Art.

When evaluating the results of pulse oximetry, one should bear in mind a rather large error of the method, reaching ± 4-5%. It should also be remembered that the results of an indirect determination of oxygen saturation depend on many other factors. For example, from the presence on the nails of the examined varnish. The varnish absorbs part of the radiation from the anode with a wavelength of 660 nm, thereby underestimating the values ​​of the SaO 2 index.

The readings of the pulse oximeter are affected by a shift in the hemoglobin dissociation curve that occurs under the influence of various factors (temperature, blood pH, PaCO2 level), skin pigmentation, anemia at a hemoglobin level below 50-60 g/l, etc. For example, small pH fluctuations lead to significant changes indicator SaO2, with alkalosis (for example, respiratory, developed against the background of hyperventilation), SaO2 is overestimated, with acidosis - underestimated.

In addition, this technique does not allow taking into account the appearance in the peripheral blood of pathological varieties of hemoglobin - carboxyhemoglobin and methemoglobin, which absorb light of the same wavelength as oxyhemoglobin, which leads to an overestimation of SaO2 values.

Nevertheless, pulse oximetry is currently widely used in clinical practice, in particular, in departments intensive care and resuscitation for a simple approximate dynamic monitoring of the state of saturation of hemoglobin with oxygen.

Assessment of hemodynamic parameters

For a complete analysis of the clinical situation in acute respiratory failure, it is necessary to dynamically determine a number of hemodynamic parameters:

• blood pressure;
• heart rate (HR);
• central venous pressure (CVP);
• pulmonary artery wedge pressure (PWP);
• cardiac output;
• ECG monitoring (including for the timely detection of arrhythmias).

Many of these parameters (BP, heart rate, SaO2, ECG, etc.) make it possible to determine modern monitoring equipment in intensive care and resuscitation departments. In severely ill patients, it is advisable to catheterize the right heart with the installation of a temporary floating intracardiac catheter to determine CVP and PLA.

Currently clinical physiology of respiration— one of the most rapidly developing scientific disciplines with its inherent theoretical foundations, methods and tasks. Numerous research methods, their increasing complexity and rising cost make it difficult to master them in practical public health. Many new methods for studying various breathing parameters are still under research; there are no clear indications for their use, criteria for quantitative and qualitative assessment.

In practical work, spirography, pneumotachometry and methods for determining the residual volume of the lungs remain the most common. The complex use of these methods allows you to get quite a lot of information.

When analyzing the spirogram, the tidal volume (TO) is assessed- the amount of air inhaled and exhaled during quiet breathing; respiratory rate in 1 min (RR); minute volume of breath (MOD = TO x BH); vital capacity (VC) - the volume of air that a person can exhale after a maximum breath; curve of forced vital capacity (FVC), which is recorded when performing a full exhalation with maximum effort from the position of maximum inspiration at a high recording speed.

From the FVC curve, the forced expiratory volume in the first second (FEV 1) is determined, the maximum ventilation of the lungs (MVL) during breathing with an arbitrary maximum depth and frequency. R. F. Klement recommends performing MVL at a given volume of breathing, not exceeding the volume of the rectilinear part of the FVC curve, and with a maximum frequency.

Measurement of functional residual capacity (FRC) and residual lung volume (ROL) significantly complements spirography, allowing you to study the structure of total lung capacity (TLC).

A schematic representation of the spirogram and the structure of the total lung capacity is shown in the figure.

OEL - total lung capacity; FRC - functional residual capacity; E vd - air capacity; ROL, residual lung volume; VC - vital capacity of the lungs; RO vd — inspiratory reserve volume; RO vyd — expiratory reserve volume; DO - tidal volume; FVC - forced vital capacity curve; FEV 1 — one second forced expiratory volume; MVL - maximum ventilation of the lungs.

Two relative indicators are calculated from the spirogram: the Tiffno index (the ratio of FEV 1 to VC) and the air velocity indicator (PSVV) - the ratio of MVL to VC.

The analysis of the obtained indicators is carried out by comparing them with the proper values, which are calculated taking into account growth in centimeters (P) and age in years (B).

Note. When using a SG spirograph, the due FEV 1 decreases in men by 0.19 liters, in women by 0.14 liters. In persons aged 20 years, VC and FEV, approximately 0.2 liters less than at the age of 25 years; in persons over 50 years old, the coefficient when calculating the due MVL is reduced by 2.

For the ratio of FFU / OEL, a general standard is established for persons of both sexes, regardless of age, equal to 50 ± 6% [Kanaev N. N. et al., 1976].

The use of the above standards OOL / OEL, FOE / OEL and VC allows you to determine the proper values ​​​​of OEL, FOE and OOL.

With the development of obstructive syndrome, there is a decrease in absolute speed indicators (FEV 1 and MVL), exceeding the degree of decrease in VC, as a result of which relative speed indicators (FEV / VC and MVL / VC) decrease, characterizing the severity of bronchial obstruction.

The table shows the limits of the norm and the gradation of the deviation of external respiration indicators, which allow you to correctly evaluate the data obtained. However, with severe violations of bronchial patency, there is also a significant decrease in VC, which makes it difficult to interpret the data of spirography, differentiation of obstructive and mixed disorders.

A regular decrease in VC with increasing bronchial obstruction was demonstrated and justified by B. E. Votchal and N. A. Magazanik (1969) and is associated with a decrease in the lumen of the bronchi due to a weakening of the elastic recoil of the lungs and a decrease in the volume of all lung structures. The narrowing of the lumen of the bronchi and especially the bronchioles on exhalation leads to such an increase in bronchial resistance that further exhalation is impossible even with maximum effort.

It is clear that the smaller the lumen of the bronchi during exhalation, the sooner they will fall to a critical level. In this regard, with severe violations of bronchial patency great importance acquires an analysis of the structure of the TRL, revealing a significant increase in the TRL along with a decrease in VC.

Domestic authors attach great importance to the analysis of the structure of the OEL [Dembo A. G., Shapkaits Yu. M., 1974; Kanaev N. N., Orlova A. G., 1976; Klement R. F., Kuznetsova V. I., 1976, et al.] The ratio of FRC and inspiratory capacity (E vd) to a certain extent reflects the ratio of the elastic forces of the lung and chest, since the level of calm exhalation corresponds to the equilibrium position of these forces. An increase in FRC in the structure of the HL in the absence of a violation of bronchial patency indicates a decrease in the elastic recoil of the lungs.

Obstruction of the small bronchi leads to changes in the structure of the TRL, primarily an increase in the TRL. Thus, an increase in TRL with a normal spirogram indicates obstruction of the peripheral airways. The use of general plethysmography makes it possible to detect an increase in OOL with normal bronchial resistance (R aw) and to suspect obstruction of the small bronchi earlier than the determination of OOL by the helium mixing method [Kuznetsova VK, 1978; KriStufek P. et al., 1980].

However, V. J. Sobol, S. Emirgil (1973) indicate the unreliability of this indicator for the early diagnosis of obstructive pulmonary diseases due to the large fluctuation in normal values.

Depending on the mechanism of bronchial obstruction, changes in VC and speed indicators have their own characteristics [Kanaev N. N., Orlova A. G., 1976]. With the predominance of the bronchospastic component of the obstruction, an increase in the TRL occurs, despite the increase in the TOL, the VC decreases slightly compared to the speed indicators.

With the predominance of bronchial collapse on exhalation, there is a significant increase in TRL, which is usually not accompanied by an increase in TRL, which leads to a sharp decrease in VC along with a decrease in speed indicators. Thus, the characteristics of a mixed variant of ventilation disorders due to peculiarities of bronchial obstruction are obtained.

The following rules apply to assess the nature of ventilation disturbances.

The rules used to evaluate options for ventilation disorders [according to N. N. Kanaev, 1980]

The assessment is made according to the indicator, reduced to a greater extent in accordance with the gradations of deviation from the norm. The first two of the presented options are more common in chronic obstructive bronchitis.

With pneumotachometry (PTM), peak (maximum) airflow velocities are determined, which are called pneumotachometric inspiratory and expiratory power (M and M c). Evaluation of PTM indicators is difficult, since the results of the study are very variable and depend on many factors. Various formulas have been proposed to determine the proper values. G. O. Badalyan proposes to consider due Mex equal to 1.2 VC, A. O. Navakatikyan - 1.2 due VC.

PTM is not used to assess the degree of ventilation disorders, but is important for the study of patients in dynamics and pharmacological tests.

Based on the results of spirography and pneumotachometry, a number of other indicators are determined, which, however, have not found wide application.

Gensler Airflow Index: ratio of MVL to due MVL, %/ratio of VC to due VC, %.

Amatuni index: Tiffno index/Ratio of VC to VC, %.

Indicators Mvyd / VCL and Mvyd / DZhEL, corresponding to the indicators obtained from the analysis of the spirogram FEV 1 / VCL and FEV 1 / DZhEL [Amatuni V. G., Akopyan A. S., 1975].

Decreased M vyd FEV 1 , increased R characterize the defeat of large bronchi (the first 7 - 8 generations).

"Chronic non-specific lung diseases",
N.R. Paleev, L.N. Tsarkova, A.I. Borokhov

Identification of isolated obstruction of the peripheral sections of the bronchial tree is an important problem in the functional diagnosis of respiration, since modern ideas the development of an obstructive syndrome begins precisely with the defeat of the peripheral bronchi, and the pathological process at this stage is still reversible. For these purposes, a number of functional methods are used: a study of the frequency dependence of lung compliance, volume ...

On a conventional radiograph in chronic bronchitis, as a rule, it is not possible to detect symptoms that characterize the actual lesion of the bronchi. These negative radiological findings are supported by morphological studies indicating that the inflammatory changes in the bronchial wall are not sufficient to make the bronchi previously invisible on the radiograph visible. However, in some cases it is possible to detect radiological changes associated with ...

Diffuse increase in the transparency of the lung fields is considered the most important radiological sign of emphysema. BE Votchal (1964) emphasized the extreme unreliability of this symptom due to its extreme subjectivity. Along with this, large emphysematous bullae and locally pronounced swelling of individual sections of the lung can be detected. Large emphysematous bullae with a diameter of more than 3-4 cm look like a limited field of increased transparency ...

With the development of pulmonary hypertension and chronic cor pulmonale, certain radiological signs. The most important of them should include a decrease in the caliber of small peripheral vessels. This symptom develops as a result of generalized vascular spasm due to alveolar hypoxia and hypoxemia, and is a fairly early symptom of impaired pulmonary circulation. Later, the already indicated expansion of the large branches of the pulmonary artery is noted, which creates a symptom ...

Bronchography significantly expands the possibilities of diagnosing chronic bronchitis. The frequency of detection of signs of chronic bronchitis depends on the duration of the disease. In patients with a disease duration of more than 15 years, the symptoms of chronic bronchitis are determined in 96.8% of cases [Gerasin V. A. et al., 1975]. Bronchography is not mandatory in chronic bronchitis, but is of great importance in diagnosing it ...