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Residual lung volume (RLV) and total lung capacity (TLC). Methods for assessing acid-base status

Currently, clinical respiratory physiology- one of the fastest growing scientific disciplines with its inherent theoretical foundations, methods and tasks. The numerous research methods, their increasing complexity and rising costs make it difficult for them to be adopted by practical healthcare. Many new methods for studying various breathing parameters are still under research; There are no clear indications for their use, or criteria for quantitative and qualitative assessment.

In practical work, spirography, pneumotachometry and methods for determining residual lung volume remain the most common. The integrated use of these methods allows one to obtain quite a lot of information.

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

From the FVC curve, the forced expiratory volume in the first second (FEV 1) and maximum pulmonary ventilation (MVL) are determined when breathing with an arbitrary maximum depth and frequency. R. F. Clement recommends performing MVL at a given respiratory volume, not exceeding the volume of the straight part of the FVC curve, and with a maximum frequency.

Measurement of functional residual capacity (FRC) and residual lung volume (RLV) significantly complements spirography, allowing one 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 air - air capacity; ROL—residual lung volume; Vital capacity - vital capacity of the lungs; RO ind — inspiratory reserve volume; RO exhalation reserve volume; DO - tidal volume; FVC - forced vital capacity curve; FEV 1 - one-second forced expiratory volume; MVL - maximum ventilation.

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

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

Note. When using the SG spirograph, the required FEV 1 decreases in men by 0.19 l, in women by 0.14 l. In persons aged 20 years, vital capacity and FEV are approximately 0.2 l less than at the age of 25 years; for persons over 50 years of age, the coefficient when calculating the proper international level is reduced by 2.

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

The use of the given standards of TLC/TLC, FRC/TLC and VC allows us to determine the proper values ​​of TLC, FRC and TLC.

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 normal limits and gradations of deviations in external respiration indicators, which allow you to correctly evaluate the data obtained. However, with severe disturbances of bronchial obstruction, a significant decrease in vital capacity is also observed, which complicates the interpretation of spirography data and the differentiation of obstructive and mixed disorders.

A natural decrease in vital capacity as bronchial obstruction intensifies was demonstrated and substantiated 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 traction of the lungs and a decrease in the volume of all pulmonary structures. The narrowing of the lumen of the bronchi and especially the bronchioles during 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 collapse to a critical level. In this regard, in case of severe disturbances of bronchial obstruction, analysis of the structure of the TLC becomes of great importance, revealing a significant increase in the TLC along with a decrease in VC.

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

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

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

Depending on the mechanism of bronchial obstruction, changes in vital capacity and speed indicators have their own characteristics [Kanaev N. N., Orlova A. G., 1976]. When the bronchospastic component of obstruction predominates, TLC increases, despite the increase in TLC, vital capacity decreases slightly compared to speed indicators.

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

To assess the nature of ventilation problems, the following rules apply.

Rules used to assess options for ventilation problems [according to Kanaev N.N., 1980]

The assessment is made according to the indicator that is 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) air flow velocities are determined, which are called pneumotachometric power of inhalation and exhalation (M and M in). Assessing PTM indicators is difficult because the study results are very variable and depend on many factors. Various formulas have been proposed to determine the proper values. G. O. Badalyan proposes to consider the due M equal to 1.2 vital capacity, A. O. Navakatikyan - 1.2 due vital capacity.

PTM is not used to assess the degree of ventilation impairment, but is important for studying patients over time and conducting pharmacological tests.

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

Gensler Air Flow Index: ratio of MVL to proper MVL, %/ratio of vital capacity to proper vital capacity, %.

Amatuni index: Tiffno index/Ratio of vital capacity to vital capacity, %.

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

A decrease in M ​​eq FEV 1 and an increase in R characterize damage to large bronchi (the first 7 - 8 generations).

"Chronic nonspecific lung diseases"
N.R.Paleev, L.N.Tsarkova, A.I.Borokhov

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

On a regular radiograph in chronic bronchitis, as a rule, it is not possible to detect symptoms characterizing the actual damage to the bronchi. These negative radiological data are confirmed by morphological studies indicating that inflammatory changes in the bronchial wall are not sufficient to make the bronchi, previously invisible on the radiograph, become visible. However, in some cases it is possible to identify radiological changes associated with...

A diffuse increase in the transparency of the lung fields is considered the most important radiological sign of pulmonary emphysema. B. E. 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 areas of the lung may be detected. Large emphysematous bullae with a diameter of more than 3 - 4 cm have the appearance of a limited field of increased transparency...

With the development of pulmonary hypertension and chronic cor pulmonale, certain radiological signs appear. The most important of them is a decrease in the caliber of small peripheral vessels. This symptom develops as a result of generalized vascular spasm caused by 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...

Bronchographic examination significantly expands the possibilities for 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, symptoms of chronic bronchitis are detected in 96.8% of cases [Gerasin V. A. et al., 1975]. Bronchographic examination is not mandatory for chronic bronchitis, but is of great importance in diagnosing it...

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 (DO, RO vd, ROvyd, VC, Evd, or, respectively, VT, IRV, ERV, VC and 1C), which makes it possible to assess the advantage and degree of obstructive pulmonary ventilation disorders. Restrictive disorders can only be reliably diagnosed if UN are not combined with impaired bronchial obstruction, i.e. in the absence of secret pulmonary ventilation disorders. However, in a doctor’s practice, more often BCQF0 Such mixed disorders occur (for example, in chronic but structural bronchitis or bronchial asthma, complicated by emphysema and pneumos!lerosis, etc.). In these cases, the mechanisms of pulmonary ventilation impairment can only be identified by analyzing the structure of the TLC.

To solve this problem, it is necessary to use additional methods for determining the functional residual capacity (FRC, or FRC) and calculate BYE both residual lung volume (RV, or RV) and total lung capacity (TLC, or TLC). Because FRC is the amount of air remaining in the lungs after maximum exhalation, it is measured only indirect methods(gas analytical or using whole body plethysmography).

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

Helium dilution method. Helium is known to be inert and harmless For the body with gas, 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 a closed spirometer container before and after mixing the gas with the lung volume (Fig. 2.38). An indoor spirometer with a known volume (V c „) is filled with a gas mixture consisting of oxygen and helium. In this case, the volume occupied by helium (V U1) and its initial concentration (Fnej) are also known (Fig. 2.38, a). After a quiet exhalation, the patient begins to breathe from the spirometer, and helium is evenly distributed between the lung volume (FRC, or FRC) and the spirometer volume (V c „; Fig. 2.38, b). After a few minutes, the concentration of helium in the general system (“spirometer-lungs”) decreases (PH e2) -

The calculation of FRC (FRC) is based on the law of conservation of matter: the total amount of helium equal to the product of its volume (V) and concentration (¥ts k), should be the same in the initial state and after mixing with lung volume (FRC, or FR*)


VcпxF lll. l =(V CII + ФOE)xF l


"(using the volume of the spirograph (V c „) and the helium concentration before and after the study (corresponding K1 and "pio, Fuej and Fhc2)> you can calculate the desired pulmonary volume (FRC, or FRC):

After this, the residual lung volume (RV, or RV) and total lung volume (TLC, or TLC) are calculated:

OOL = FOE - RO ext;

OEL = vital capacity + OOL.

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


The accuracy of both methods for determining FRC (FRC) depends on the water change in the lungs, which occurs within a few minutes in healthy people. However, in some diseases accompanied by severe unevenness of ventilation (for example, with obstructive pulmonary pathology), balancing the concentration of gases takes a long time. In these cases, FRC measurements using the methods described may be inaccurate. The more technically complex method of whole body plethysmography does not have these disadvantages.

Whole body plethysmography. The whole body plethysmography method is one of the most informative and complex research methods used in pulmonary polo! nor for determining pulmonary volumes, tracheal resistance, elastic properties of lung tissue and chest, as well as for assessing some other parameters of pulmonary ventilation.

The integral plethysmograph is a hermetically sealed chamber with a volume of M 800 l, in which the patient can freely accommodate (Fig. 2.39 and 2.40). The subject breathes through a non-neumotachographic tube connected to a hose open to the atmosphere. The hose has a damper that allows you to automatically shut off the air flow at the right time. Special barometric sensors measure the pressure in the chamber O"kam) and in the oral cavity (P, ut). The latter, with the hose valve closed, is equal to the intra-alveolar pressure. The pneumotachograph allows you to determine the air flow (V).

The operating principle of the integral plethysmograph is based on Boyaya-Moriysh law, according to which, at a constant temperature, the relationship between pressure (P) and volume of gas (V) remains constant:

P, x V, = P 2 x V 2,

where Pi is the initial gas pressure,

Vj is the initial volume of gas,

P> - pressure after changing gas volume,

V 2 - volume after changing gas pressure.

The patient, located inside the plethysmograph chamber, inhales and exhales, after which (at the level of FRC, or FRC), the hose valve is closed, and about* and the person trying to “inhale” and “exhale” (the “breathing” maneuver; Fig. 240) With this “breathing” maneuver, the viutralveolar pressure changes, and the pressure in the closed chamber of the plethysmograph changes in inverse proportion to it. When attempting to “inhale” with the valve closed, the volume of the chest increases, which leads, on the one hand, to a decrease in intra-alveolar pressure, and on the other, to a corresponding increase in pressure in the plethysmograph chamber (P K am) - On the contrary, when attempting to “exhale” alveolar pressure increases, and chest volume and chamber pressure decrease.


Over the past 20-30 years, much attention has been paid to the study of pulmonary function in patients with pulmonary pathology. A large number of physiological tests have been proposed that make it possible to qualitatively or quantitatively determine the state of the function of the external respiration apparatus. Thanks to the established system of functional studies, it is possible to identify the presence and degree of DN in various pathological conditions and to clarify the mechanism of breathing disorders. Functional pulmonary tests make it possible to determine the amount of pulmonary reserves and the compensatory capabilities of the respiratory organs. Functional studies can be used to quantify changes occurring under the influence of various therapeutic interventions (surgical interventions, therapeutic use of oxygen, bronchodilators, antibiotics, etc.), and, consequently, to objectively assess the effectiveness of these measures.

Functional studies occupy a large place in the practice of medical labor examination to determine the degree of disability.

General data on lung volumes The chest, which determines the boundaries of 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 quiet 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 tidal volume (TI) (normally 400-600 ml; i.e. 18% VC).

2. With maximum inhalation, an additional volume of air is introduced into the lungs - the inspiratory reserve volume (IRV), and with 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 maximum inhalation.

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

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

6. TVR + ROvyd = functional residual capacity (FRC), i.e. this is the volume occupied by the lungs 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.

To correctly assess the actual indicators obtained during the survey, proper values ​​are used for comparison, i.e. theoretically calculated individual norms. When calculating the proper indicators, gender, height, weight, and age are taken into account. When assessing, the percentage (%) ratio of the actually obtained value to the expected value is usually calculated. It must 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 gas must be reduced to body temperature (37 C), with complete saturation with water vapor. This condition is called BTPS (in Russian - TTND - body temperature, atmospheric pressure, saturation with water vapor).

When studying gas exchange, the obtained volumes of gas lead to the so-called standard conditions (STPD). i.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).

During mass surveys, an average correction factor is often used, which for the central zone of the Russian Federation 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 pulmonary 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 (toward the center) and tending to reduce the volume, and the elastic force of the chest, directed during quiet breathing mainly in the opposite direction - from the center outward. The amount of air depends on many reasons. First of all, the condition of the lung tissue itself, its elasticity, the degree of blood supply, etc. is important. However, the volume of the chest, the mobility of the ribs, the condition of the respiratory muscles, including the diaphragm, which is one of the main muscles that carry out inhalation, play a significant role.

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

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

Basic calculation indicators determined from spirograms

1. Frequency and rhythm of breathing. The normal number of respirations at rest ranges from 10 to 18-20 per minute. Using a spirogram of quiet breathing with rapid movement of the paper, you can determine the duration of the inhalation and exhalation phases and their ratio 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 exhalation increases with impaired bronchial obstruction and can be used in a comprehensive assessment of the function of external respiration. When assessing a spirogram, in some cases the rhythm of breathing and its disturbances are important. Persistent respiratory arrhythmias usually indicate dysfunction of the respiratory center.

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

MOD = DO x RR, where RR is the frequency of respiratory movements in 1 min DO - tidal volume

MOR 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 of the use of ventilated air, on the difficulties of normal ventilation, on the disruption of gas diffusion processes (their passage through membranes in the lung tissue), etc. An increase in MOR is observed with an increase in metabolic processes (thyrotoxicosis), with some lesions of the central nervous system. A decrease in MOD is observed in severely ill patients with severe pulmonary or heart failure, or 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. Using special methods, MPO 2 is calculated. Based on this, the oxygen utilization factor (OCF 2) is calculated - this is the number of milliliters of oxygen absorbed from 1 liter of ventilated air.

KIO 2 = MPO 2 in ml MOD in l

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

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

The study should be carried out under resting conditions, i.e. 1.5-2 hours after a light meal and after 10-20 minutes of rest. To determine vital capacity, various types of water and dry spirometers, gas meters and spirographs are used.

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

Vital vital capacity, in addition to the usual technique, can be recorded in two stages, i.e., after a quiet exhalation, the subject is asked to take the deepest possible breath and return to the level of quiet breathing, and then, as much as possible, exhale as much as possible.

For a correct assessment of the actually obtained vital capacity, the calculation of the proper vital capacity (VC) is used. The most widely used calculation is the Anthony formula:

VEL = DOO x 2.6 for men VEL = DOO x 2.4 for women, where DOO is the proper basal metabolic rate, determined using special tables.

When using this formula, you need to remember that the values ​​of DOO are determined under STPD conditions.

The formula proposed by Bouldin et al. has gained acceptance: 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 suggests VEL in liters in the BTPS system to be calculated 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 VC, nomograms and calculation tables were used.

Assessment of the data obtained: 1. Data that deviate from the proper value by more than 12% in men and - 15% in women should be considered reduced: normally such values ​​occur in only 10% of practically healthy individuals. Without having the right to consider such indicators obviously pathological, it is necessary to assess the functional state of the respiratory apparatus as reduced.

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

A decrease in vital capacity is caused by pathological conditions that prevent maximum expansion of the lungs (pleurisy, pneumothorax, etc.), changes in the lung tissue itself (pneumonia, lung abscess, tuberculosis) and causes not related to pulmonary pathology (limited mobility of the diaphragm, ascites and 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:

vital capacity 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 obstructive disorders In addition to the mechanical factors that determine the decrease in the decrease in VC, a certain significance is functional state of the nervous system, general condition of the patient. A pronounced decrease in vital capacity is observed in diseases of the cardiovascular system and is largely due to stagnation in the pulmonary circulation.

5. Phosphorus vital capacity (FVC) To determine FVC, spirographs with high drawing speeds (from 10 to 50-60 mm/s) are used. A preliminary study and recording of vital capacity is carried out. After a short rest, the subject takes a maximum deep breath, holds his breath for a few seconds and exhales as quickly as possible (forced exhalation).

There are various ways to assess FVC. However, our greatest recognition has been given to the definition of one-second, two- and three-second capacity, i.e., calculating the volume of air in 1, 2, 3 seconds. The one-second test is most often used.

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

According to a number of researchers (B.S. Agov, G.P. Khlopova, etc.), 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 significance. The initial part of the curve characterizes the resistance of the 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. In recent years, “peak fluorometer” devices have been developed and put into practice, which make it possible to more accurately characterize the state of the distal part of the bronchial tree. being small in size, they make it possible to monitor the degree of bronchial obstruction in patients with bronchial asthma, and to use medications in a timely manner, before the appearance of subjective symptoms of brochospasm.

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

Signs of obstructive respiratory failure:

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

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

In practical work, the determination of MVL using a spirogram is more often used. The most widely used method for determining MVL is by voluntary forced (deep) breathing with the maximum available frequency. During a spirographic study, recording begins with quiet breathing (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 gender. It is influenced by the type of occupation, training and general condition of the subject. MVL largely depends on the willpower of the subject. Therefore, for the purpose 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 MBL figures for 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 obstructive processes and during restriction; the degree of disturbance can be calculated using the formula:

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

Various formulas have been proposed for determining the proper MVL (DMVL). The most widely used definition is DMVL, which is based on Piboda’s formula, but with an increase in the 1/3 VEL proposed by him to 1/2 VEL (A.G. Dembo).

Thus, DMVL = 1/2 JEL x 35, where 35 is the respiratory rate per minute.

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

Age (years)

Calculation formula

DMVL = S x 60

DMVL = S x 55

DMVL = S x 50

DMVL = S x 40

60 and over

DMVL = S x 35

To calculate the DMVL, the Gaubatz formula is satisfactory: DMVL = DEL x 22 for persons under 45 years DMVL = DEL x 17 for persons over 45 years of age

7. Residual volume (RV) and functional residual capacity (FRC). TLC 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 VC and ROvyd. , calculate OOL, OEL and OOL/OEL.

TOL = FFU - ROvyd DOEL = JEL x 1.32, where DOEL is the proper total lung capacity.

The value of FRC and TLC is very high. As TOL increases, the uniform mixing of inhaled air is disrupted and the efficiency of ventilation decreases. TOL increases with emphysema and bronchial asthma.

FRC and TLC decrease with pneumosclerosis, pleurisy, pneumonia.

Limits of the norm and gradation of deviations from the norm of breathing parameters

Indicators

Conditional norm

Degrees of change

moderate

significant

Vital capacity, % due

MVL, % due

FEV1/VC, %

TEL, % due

OOL, % due

OOL/OEL, %


OEL

1. Small medical encyclopedia. - M.: Medical encyclopedia. 1991-96 2. First aid. - M.: Great Russian Encyclopedia. 1994 3. Encyclopedic Dictionary of Medical Terms. - M.: Soviet Encyclopedia. - 1982-1984.

See what "OEL" is in other dictionaries:

    OEL- total lung capacity Dictionary: S. Fadeev. Dictionary of abbreviations of the modern Russian language. St. Petersburg: Politekhnika, 1997. 527 pp.... Dictionary of abbreviations and abbreviations

    See Total Lung Capacity... Large medical dictionary

    OEL- total lung capacity... Dictionary of Russian abbreviations

    - (TEL; synonym: total lung volume in old people) the volume of air contained in the lungs after maximum inspiration... Large medical dictionary

    - (TEL; syn. total lung volume obsolete) the volume of air contained in the lungs after maximum inspiration ... Medical encyclopedia

    I Vital capacity of the lungs (VC) is the maximum amount of air exhaled after the deepest inhalation. Vital vital capacity is one of the main indicators of the condition of the external respiration apparatus, widely used in medicine. Along with the remaining volume... Medical encyclopedia

    Volumes of air contained in the lungs at different degrees of chest expansion. At max. During exhalation, the gas content in the lungs decreases to the residual volume of OO; in the position of normal exhalation, a reserve volume is added to it... ... Great Soviet Encyclopedia

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For what disease: ASTHMA

[ASTHMA prototype, MP 900]

3) OOL/OOL predicted:

TEL (plethysmographic) observed/predicted: 139

5) FJE/FJE predicted:

[NORMAL prototype, MP 500]

FEV1/FEF ratio: 40

[Prototype JSC, MP 900]

PSOU/PSOU predicted: 117

[NORMAL prototype, MP 7dO]

8) Change in FEV1 (after taking bronchodilators): 31

9) UPMS/UPMS predicted:

[Prototype JSC, MP 900]

Tilt P5025: 9

[Prototype JSC, MP 900]

Let's take a closer look at one of the questions in this protocol.

6) FEV1/FZH ratio: 40 [Prototype JSC, KU900]

The abbreviations in these lines indicate the found prototypes of diseases, MP means “measure of likelihood”, OOL, OEL, FVZh, etc. - results of laboratory tests and measurements of pulmonary functions:

RLV - residual lung volume, liters;

TLC - total lung capacity, liters;

FOUQUET - forced vital capacity, liters;

FEV1 - forced expiratory volume in 1 s, liters;

PSOU - penetration ability for carbon monoxide.

The user-entered value of 40 for the ratio of forced expiratory volume in 1 s (FEV1) to forced vital capacity (FVC) prompts the system to activate the OAO prototype (Obstructive Airways Dicease) with a plausibility measure of this hypothesis of 900.

The value of the likelihood measure of a particular hypothesis is selected in the range from -1000 to 1000 solely for reasons of simplifying calculations. This parameter reflects the degree of confidence of the system in the validity of the put forward (activated) hypothesis based on the available data on a specific medical history. In fact, when determining the likelihood measure, the system compares the data entered by the user with those stored in the slots of the candidate prototype. The obtained values ​​serve as the basis for choosing the most plausible of the available hypotheses (prototypes). The purpose of the likelihood measure parameter in the CENTAUR system is the same as the confidence coefficient in the MYCIN and EMYCIN systems, and the same algorithms are used for operations with likelihood measures as for operations with confidence coefficients. Please note that during the dialogue with the user, the system does not explain why this particular value of the likelihood measure was chosen and not another. For the user, the algorithm for calculating the likelihood measure is a “black box”.

In fully rule-based expert systems, the trace log typically displays only those inputs that activate the rule that receives the highest score in resolving the conflict. In such a situation, the user can only guess how the system responded to data that was entered but not mentioned in the protocol. As can be seen in the above log of dialogue with the user, the CENTAUR program immediately lets the user know what preliminary considerations aroused the entered values ​​of individual parameters.

After the dialogue is completed, the system presents the user with its “considerations” regarding the entered data.

Hypothesis: ASTHMA, MP: 900. Reason: previous diagnosis - ASTHMA

Hypothesis: NORMAL, MP: 500. Reason: FFE is 81

Hypothesis: OAO, MP: 900. Reason: FEV1/FEF ratio is 40

Hypothesis: NORMAL, MP: 700. Reason: PSOU is 117

Hypothesis: JSC, MP: 900. Reason: UPMS is 12

Hypothesis: JSC, MP: 900. Reason: slope P5025 is 9

The most plausible hypotheses: NORMAL, JSC [New analyzed prototypes: NORMAL, JSC]

From this printout it follows that the system will then focus on the two most plausible hypotheses: NORMAL and OAD. These two hypotheses are direct "heirs" of the PULMONARY-DISEASE prototype. Consideration of the ASTHMA hypothesis is postponed for the time being because it is a subtype of the OAD hypothesis. This hypothesis will be examined in the process of refining the OAD hypothesis, in full accordance with the top-down refinement strategy. The hierarchical structure of the hypothesis space makes it possible to provide the user with complete and clear information about how this strategy is implemented in the expert system. In completely rule-based systems, the user must be aware of the system's strategy for resolving conflicts between competing rules, and only then can he understand why, in a particular situation, the hypothesis recorded in the printout of the trace result was preferred. and not any other.

Please note that not all data entered by the user during the initial dialogue leads to the selection of candidate hypotheses, and several prototypes are included in the list of candidate hypotheses. When filling in data from the two hypotheses selected in this list - NORMAL and OAD - a parameter such as TLC (total lung capacity), which during the dialogue did not affect the initial list, will be taken into account and, quite possibly, will affect the value of the likelihood measure of the analyzed hypothesis. The value of this parameter (139) causes the system to question the plausibility of the NORMAL hypothesis, as will be shown below in the example of printing out the values ​​of those parameters that led the system “to confusion”. Data that does not fit into the range represented in the slots of certain prototypes causes the system to reduce the likelihood of the corresponding hypothesis.

!.Unexpected value: OOL is 261 in NORMAL, MP: 700

!Unexpected value: OEL is 139 in NORMAL, MP: 400

!Unexpected value: FEV1/FVC is 40 in NORMAL, MP: -176

!Unexpected value: UPMS is 12 in NORMAL, MP: -499

!Unexpected value: P5025 is 9 in NORMAL, MP: -699

From the presented printout it is clear that, although based on the results of a preliminary express analysis of the entered data, the NORMAL hypothesis seemed very plausible, a more detailed study of the entire set of data, in particular the five parameters included in the printout, made the system highly doubtful about its validity. The user can obtain all this information from the printouts that the CENTAUR system produces during operation. Then a list of hypotheses is generated, which is ordered in descending order, with the JSC prototype in first place:

List of hypotheses: (OAO 999) (NORMAL -699)

The OAO hypothesis is being tested (AIRWAY OBTURATION)

Next, the system will confirm the hypothesis that the patient suffers from obstruction of the airways, and the degree of the disease is serious, and the subtype of the disease is asthmatic. After this, the system moves to the stage of clarifying the diagnosis. At this stage, the user is asked additional questions, the answers to which provide the information necessary for this. This stage is performed under the control of special refinement rules, which are stored in the slots of the corresponding prototype. The protocol for a fragment of a clarifying dialogue with the user is given below.

[Implementation of clarifying rules...]

20) Number of pack-years of smoking: 17

How long ago did the patient quit smoking: 0

Difficulty breathing: NO

After the clarification dialogue is completed, the rules come into play, forming the conclusion for this consultation session. These rules are specific to each of the possible prototypes, and at the end of the session, the set of rules that is associated with the prototype of the selected hypothesis is executed. A set of rules of this type associated with the OAD prototype is given below.

[The actions specified in the ACTION slot of the OJSC prototype are performed...]

Conclusion: indications supporting the diagnosis of “Obstruction of the airways” are as follows:

Increased lung volumes indicate hyperfilling.

An increased value of the TLC/TLC ratio is consistent with the presence of severe obstruction of the airways. Forced vital capacity is normal, but the FEV1/FVC ratio is low, indicating severe airway obstruction.

A low average exhaled flow is consistent with the presence of severe airway obstruction. Obstruction of the airways is indicated by the curvature of the dependence of air flow on volume.