The concept of human lung volume. Research methods and indicators of external respiration

VITAL CAPACITY

Vital capacity of the lungs(VC) - the maximum amount of air exhaled after the deepest breath. VC is one of the main indicators of the state of the external respiration apparatus, widely used in medicine.

Together with the residual volume, i.e. the volume of air remaining in the lungs after the deepest exhalation, the VC forms the total lung capacity (TLC). Normally, VC is about 3/4 of the total lung capacity and characterizes the maximum volume within which a person can change the depth of his breathing. With calm breathing, a healthy adult uses a small part of the VC: inhales and exhales 300-500 ml air (called tidal volume). At the same time, the inspiratory reserve volume, i.e. the amount of air that a person is able to inhale additionally after a quiet breath, and the expiratory reserve volume, equal to the volume of additionally exhaled air after a quiet exhalation, averages about 1500 ml each. During exercise, tidal volume increases by using the inspiratory and expiratory reserves.

VC is determined using spirography. The value of VC normally depends on the gender and age of a person, his physique, physical development, and with various diseases it can significantly decrease, which reduces the ability of the patient's body to adapt to physical activity. To assess the individual value of VC in practice, it is customary to compare it with the so-called due VC (JEL), which is calculated using various empirical formulas. So, based on the height of the subject in meters and his age in years (B), JEL (in liters) can be calculated using the following formulas: for men, JEL \u003d 5.2´ height - 0.029´ B - 3.2; for women JEL = 4.9´ height - 0.019´ B - 3.76; for girls from 4 to 17 years old with height from 1 to 1.75 m JEL \u003d 3.75´ height - 3.15; for boys of the same age with growth up to 1.65 m JEL \u003d 4.53´ growth - 3.9, and with growth over 1.65 m-JEL \u003d 10´ height - 12.85.

Exceeding the proper VC values of any degree is not a deviation from the norm; in physically developed people involved in physical education and sports (especially swimming, boxing, athletics), individual VC values sometimes exceed VC by 30% or more. VC is considered reduced if its actual value is less than 80% VC.

Decreased lung capacity most often observed in diseases of the respiratory system and pathological changes in the volume of the chest cavity; in many cases, it is one of the important pathogenetic mechanisms of development respiratory failure . A decrease in VC should be assumed in all cases when the patient's performance of moderate physical activity is accompanied by a significant increase in breathing, especially if the examination reveals a decrease in the amplitude of respiratory oscillations of the chest walls, and according to percussion of the chest, restriction of respiratory excursions of the diaphragm and (and) its high standing is established . As a symptom of certain forms of pathology, a decrease in VC, depending on its nature, has a different diagnostic value. In practice, it is important to distinguish between a decrease in VC due to an increase in the residual volume of the lungs (redistribution of volumes in the structure of the TEL) and a decrease in VC due to a decrease in the TRL.

Due to the increase in the residual volume of the lungs, VC decreases with bronchial obstruction with the formation of acute pulmonary distention (see. Bronchial asthma ) or emphysema . For the diagnosis of these pathological conditions, a decrease in VC is not a highly significant symptom, but it plays a significant role in the pathogenesis of respiratory failure developing in them. With this mechanism for reducing VC, the total airiness of the lungs and TFR, as a rule, are not reduced and can even be increased, which is confirmed by direct measurement of TFR using special methods, as well as by percussion-determined low standing of the diaphragm and an increase in percussion tone above the lungs (up to "box tone"). » sound), expansion and increase in the transparency of the lung fields according to X-ray examination. A simultaneous increase in residual volume and a decrease in VC significantly reduce the ratio of VC to the volume of ventilated space in the lungs, which leads to ventilation respiratory failure. Increased respiration could compensate for the decrease in VC in these cases, but with bronchial obstruction, the possibility of such compensation is sharply limited due to forced prolonged exhalation, therefore, with a high degree of obstruction, a decrease in VC, as a rule, leads to severe hypoventilation of the pulmonary alveoli and the development of hypoxemia. Decreased VC due to acute pulmonary distention is reversible.

The reasons for the decrease in VC due to a decrease in the TEL can be either a decrease in the capacity of the pleural cavity (thoracophrenic pathology), or a decrease in the functioning lung parenchyma and pathological rigidity of the lung tissue, which formulates a restrictive, or restrictive, type of respiratory failure. Its development is based on a decrease in the area of diffusion of gases in the lungs due to a decrease in the number of functioning alveoli. The ventilation of the latter is not significantly disturbed, because the ratio of VC to the volume of the ventilated space in these cases does not decrease, but more often increases (due to a simultaneous decrease in the residual volume); increased breathing is accompanied by hyperventilation of the alveoli with signs of hypocapnia (see. Gas exchange ). From thoracophrenic pathology, a decrease in VC and HL most often cause a high standing of the diaphragm, for example, with ascites obesity (see pickwickian syndrome ), massive pleural effusion (with hydrothorax , pleurisy , mesothelioma pleura ) and extensive pleural adhesions, pneumothorax pronounced kyphoscoliosis. The range of lung diseases accompanied by restrictive respiratory failure is small and includes mainly severe forms of pathology: pulmonary fibrosis in berylliosis, sarcoidosis , Hammen-Rich syndrome (see. Alveolitis ), diffuse connective tissue diseases , pronounced focal-diffuse pneumosclerosis , the absence of a lung (after pulmonectomy) or part of it (after lung resection).

A decrease in TL is the main and most reliable functional and diagnostic symptom of pulmonary restriction. However, prior to the measurement of RCL, which requires special equipment rarely used in polyclinics and district hospitals, the main indicator of restrictive respiratory disorders is a decrease in VC as a reflection of a decrease in RCL. The latter should be considered when a decrease in VC is detected in the absence of pronounced violations of bronchial patency, as well as in cases where it is combined with signs of a decrease in the total air capacity of the lungs (according to percussion and X-ray examination) and a high standing of the lower borders of the lungs. Diagnosis is facilitated if the patient has inspiratory dyspnea, characteristic of restriction, with a short labored inhalation and rapid exhalation at an increased respiratory rate.

In patients with reduced VC at certain intervals, it is advisable to repeat its measurements in order to monitor the dynamics of respiratory functions and evaluate the ongoing treatment.

What affects lung capacity

The level of filling the lungs with air is influenced by certain circumstances. In men, the average organ volume is larger than in women. In tall people with a large body constitution, the lungs can hold more air on inspiration than in short and thin people. With age, the amount of inhaled air decreases, which is a physiological norm.

Regular smoking reduces lung capacity. Low fullness is characteristic of hypersthenics (short people with a rounded body, shortened broad-boned limbs). Asthenics (narrow-shouldered, thin) are able to inhale more oxygen.

All people living high relative to sea level (mountainous areas) have reduced lung capacity. This is due to the fact that they breathe rarefied air with low density.

Temporary changes in the respiratory system occur in pregnant women. The volume of each lung is reduced by 5-10%. The rapidly growing uterus increases in size, presses on the diaphragm. This does not affect the general condition of the woman, since compensatory mechanisms are activated. Due to accelerated ventilation, they prevent the development of hypoxia.

Average lung volume

The volume of the lungs is measured in liters. Average values are calculated during normal breathing at rest, without deep breaths and full exhalations.

On average, the figure is 3-4 liters. In physically developed men, the volume with moderate breathing can reach up to 6 liters. The number of respiratory acts is normally 16-20. With active physical exertion, nervous strain, these figures increase.

ZHOL, or vital capacity of the lungs

VC is the maximum capacity of the lung during maximum inhalation and exhalation. In young, healthy men, the indicator is 3500-4800 cm 3, in women - 3000-3500 cm 3. For athletes, these figures increase by 30% and amount to 4000-5000 cm 3. Swimmers have the largest lungs - up to 6200 cm 3.

Considering the phases of ventilation of the lungs, the following types of volume are divided:

respiratory - air freely circulating through the bronchopulmonary system at rest;
reserve on inspiration - air filled by the organ during maximum inspiration after a calm exhalation;
reserve on exhalation - the amount of air removed from the lungs during a sharp exhalation after a calm breath;
residual - the air remaining in the chest after maximum exhalation.

Airway ventilation refers to gas exchange for 1 minute.

The formula for its definition:

tidal volume × number of breaths/minute = minute volume of breath.

Normally, in an adult, ventilation is 6-8 l / min.

Table of indicators of the norm of the average lung volume:

The air that is in such parts of the respiratory tract does not participate in gas exchange - the nasal passages, nasopharynx, larynx, trachea, central bronchi. They constantly contain a gas mixture called "dead space", and is 150-200 cm 3.

VC measurement method

External respiratory function is examined using a special test - spirometry (spirography). The method fixes not only the capacity, but also the speed of circulation of the air flow.
For diagnosis, digital spirometers are used, which have replaced mechanical ones. The device consists of two devices. A sensor for fixing the air flow and an electronic device that converts measurements into a digital formula.

Spirometry is prescribed for patients with impaired respiratory function, broncho-pulmonary diseases of a chronic form. Evaluate calm and forced breathing, conduct functional tests with bronchodilators.

Digital data of VC during spirography are distinguished by age, sex, anthropometric data, absence or presence of chronic diseases.

Formulas for calculating individual VC, where P is height, B is weight:

for men - 5.2 × P - 0.029 × B - 3.2;
for women - 4.9 × P - 0.019 × B - 3.76;
for boys from 4 to 17 years old with growth up to 165 cm - 4.53 × R - 3.9; with growth over 165 cm - 10 × R - 12.85;
for girls from 4 to 17 years old, swarms grow from 100 to 175 cm - 3.75 × R - 3.15.

Measurement of VC is not carried out in children under 4 years of age, patients with mental disorders, with maxillofacial injuries. Absolute contraindication - acute contagious infection.

Diagnostics is not prescribed if it is physically impossible to conduct a test:

neuromuscular disease with rapid fatigue of the striated muscles of the face (myasthenia gravis);
postoperative period in maxillofacial surgery;
paresis, paralysis of the respiratory muscles;
severe pulmonary and heart failure.

Reasons for an increase or decrease in VC

Increased lung capacity is not a pathology. Individual values depend on the physical development of a person. In athletes, the YCL can exceed the standard values by 30%.

Respiratory function is considered impaired if the volume of a person's lungs is less than 80%. This is the first signal of insufficiency of the bronchopulmonary system.

External signs of pathology:

respiratory failure during active movements;

change in the amplitude of the chest.

Initially, it is difficult to determine violations, since compensatory mechanisms redistribute air in the structure of the total volume of the lungs. Therefore, spirometry is not always of diagnostic value, for example, in pulmonary emphysema, bronchial asthma. In the course of the disease, swelling of the lungs is formed. Therefore, for diagnostic purposes, percussion is performed (low position of the diaphragm, a specific “box” sound), chest x-ray (more transparent fields of the lungs, expansion of boundaries).

Decreasing factors for VC:

a decrease in the volume of the pleural cavity due to the development of a pulmonary heart;
rigidity of the parenchyma of the organ (hardening, limited mobility);
high standing of the diaphragm with ascites (accumulation of fluid in the abdominal cavity), obesity;
pleural hydrothorax (effusion in the pleural cavity), pneumothorax (air in the pleural sheets);
diseases of the pleura - tissue adhesions, mesothelioma (tumor of the inner lining);
kyphoscoliosis - curvature of the spine;
severe pathology of the respiratory system - sarcoidosis, fibrosis, pneumosclerosis, alveolitis;
after resection (removal of part of the organ).

Systematic monitoring of VC helps to track the dynamics of pathological changes, take timely measures to prevent the development of diseases of the respiratory system.

To maintain normal life, the human body needs oxygen in an amount sufficient for each specific physical condition. The volume of air required may vary depending on the degree of physical activity at a particular time, health status, age and gender of the person.

The respiratory organs and, in particular, the lungs are directly involved in providing the body with oxygen. Depending on their physical and mechanical properties, a person can expose himself to more or less intense loads, which are especially demanding on the presence of a sufficient amount of oxygen in the blood.

What is JEL?

This medical term refers to the maximum amount of air that a person can inhale after a complete exhalation and only partially characterizes the capacitive indicators of the respiratory system.

If a person can no longer continue to exhale, this does not mean that his lungs are completely empty. The content of the pulmonary alveoli, which remains in them after a complete exhalation, is called residual.

VC and residual volume form the total lung capacity (TLC). In other words, TRL is the volume of all air that the lungs can hold as a result of a maximum breath.

A residual lung volume of 3/4 of the TLC is considered normal in most cases.

At rest, a healthy body consumes an average of 0.5 liters of air per breath. After a normal exhalation, the lung tissue contains a certain volume of gas, which is called reserve. At the same time, the amount of air that can be inhaled after a normal breath is called additional.

Thus, we can distinguish the following volumes that characterize the lungs of a person:

Respiratory (normal breathing) - for a healthy person, the norm is approximately equal to 500 ml.
Reserve (residue after a normal exhalation) - 1500 ml.
Additional (allows you to inhale more air) - 1500 ml.
Residual (fills the pulmonary alveoli after a full exhalation) - 1500 ml.

Capacitive characteristics of the lungs:

VC - (sum of respiratory, reserve and additional volumes) - 4500 ml.
TRL - (the sum of vital capacity and residual lung volume). The average lung capacity is 6000 ml.
FRC - functional residual capacity - 3000 ml. The air that remains in the lungs after a normal exhalation in a resting state. In fact, this is the sum of the residual and reserve volumes of the lungs.

All of the above values are approximate values for the averageadulthealthy person. These quantitiescan significantly (30% or more) differbdepending on physical and age indicators.

Identification of deviations from the norm

To detect pathological changes in the patient's body, it is important to determine the deviations in VC from the indicators that are normal for each individual person. And since this indicator can differ significantly, special formulas were created with the help of which, based on empirical data, it is possible to calculate the so-called proper lung capacity (DZhEL), characteristic of a person with certain age and physical indicators.

To calculate the JEL, the data of obviously healthy people of a certain age, body type, sex and physical development were taken as a basis. Based on these factors, dependencies were built to calculate the coefficients that are used in the formulas for calculating the proper lung capacity of people with similar characteristics.

The most common methods for calculating JEL:

1. Anthoni's method. This method involves the use of the value of the proper total metabolism (meaning the metabolism) multiplied by the corresponding coefficients, which are taken from the tables.
2. Method developed by N. N. Kanaev. Does not use general metabolism as a correlation factor, due to the lack of a direct relationship between VC and body weight. The method is based on the use of the age, height and sex of the subject, as well as coefficients obtained on the basis of relevant data from healthy people.

According to this method, JEL for men will be calculated as follows: 0.052 x (P) - 0.029 x (B) - 3.20.

For women: 0.049 x (P) - 0.019 x (B) - 3.76.

3. Calculation of the GEL of children (authors - I.S. Shiryaev, B.A. Markov).

For boys whose height is from 1 m to 1.64 m: 4.53 x (P) - 3.9. Height from 1.65 m; 10.00 x (P) - 12.85.

For girls, from 1.00 to 1.75 m tall: 3.75 x (P) - 3.15.

(P) - height in meters, (B) - age in years.

Diagnostic methods

The most common and affordable way to determine VC is spirometry. It consists in measuring the volume of fluid displaced by the air exhaled by the subject. To obtain the most reliable results, the procedure is repeated several times and the average value (sometimes the maximum) is used as the final indicator.

Spirography is used for more accurate diagnosis. This type of examination is a graphical fixation of changes in the dynamics of breathing over a certain period of time.

What affects the vital capacity of the lungs?

The answer to this question directly depends on the state of health of the person in relation to which research is being conducted. For a healthy person, VC is largely influenced by his physical development, gender, age, occupation and lifestyle.

For example, in people who are intensively involved in outdoor sports (running, swimming, boxing, etc.), the respiratory system and, in particular, the lungs, are much more developed. The difference is especially great in comparison with people leading a sedentary lifestyle.

The human body is very rational and will not, unless absolutely necessary, create additional resources to solve non-existent tasks. The less a person is subject to any intense physical activity, the lower the volumetric and capacitive indicators of the lungs. Accordingly, the amount of oxygen that his respiratory system is able to provide is also less.

With an increase in physical activity, especially associated with intensive ventilation of the respiratory system (swimming, running), as a rule, there is an increase in VC and other capacitive characteristics of the lungs. It should be noted that these indicators should be increased only if you are confident in your own health. An increase in lung volume, which has decreased due to pathological processes in the respiratory or any other system, is fraught with serious consequences.

An increase in this parameter is possible within a fairly wide range and is not considered a pathology. Athletes and people whose activities are associated with an intensive workload of the respiratory system may experience an excess of the proper parameters by more than 30%.

Reasons for the decrease in the indicator

Regarding the reduction of VC, the opinions of medical scientists are not so unambiguous, but the majority tend to consider the situation when this parameter is less than due by 20% or more as a pathology.

Externally, the decrease can be manifested by shortness of breath, respiratory and oxygen insufficiency of varying severity. The occurrence of these symptoms, as a rule, is not observed in a calm state and they can be considered pathological due to the relatively minor loads after which they appear. The situation is especially emphasized if violations in the breathing regime are accompanied by changes in the amplitude of the oscillations of the chest cavity, a high standing of the diaphragm and the lower part of the lungs.

A decrease can be observed in the case of various diseases of the respiratory, cardiovascular systems, acute lesions of the muscular and bone tissues of the chest cavity, traumatic injuries or previous operations.

In clinical studies, the nature of the change in VC is of great diagnostic importance. Two options are most common: the first - when the TEL does not decrease; the second when it decreases.

1. Reduction due to the redistribution of respiratory volumes (TRL does not decrease) is a situation when the total volume of the lungs remains unchanged, and sometimes increases, and a decrease in VC in this case is a consequence of an increase in the residual volume of the lungs (which remains after maximum expiration).

The cause of these changes is usually acute swelling of the lungs due to the occurrence of diseases such as bronchial asthma or emphysema.

The very fact of a decrease in VC in such cases is not a significant clinical symptom and can be considered as a pathogenetic component in the development of respiratory and oxygen insufficiency. The situation is complicated by the fact that a decrease in bronchus patency does not allow compensating for insufficiency due to increased respiration.

There is some consolation in the fact that the decrease in VC due to an increase in HL is reversible and normalizes when the diseases that were the cause of pathological changes are cured.

2. Decrease in VC, as a result of a decrease in ROI. The total lung capacity may decrease due to a decrease in the number of normally functioning alveoli. In such cases, there is a decrease in the reserve volume of the lungs, the respiratory rate and ventilation of the alveoli increases, but due to the reduction in their number and functional impact, there may be an insufficiency of the external respiratory function.

The number of diseases that can cause a decrease in TRL is small: these are mainly severe pathological changes in the lungs: fibrosis, diffuse diseases of the pulmonary connective tissue, pneumosclerosis of various etiologies, postoperative condition (complete or partial removal of the lung).

In modern medicine, in patients of various ages with symptoms of respiratory diseases, one of the main diagnostic methods is the method of studying the function of external respiration (RF). This research method is the most accessible and allows assessing the ventilation functionality of the lungs, i.e. their ability to provide the human body with the necessary amount of oxygen from the air and remove carbon dioxide.

Vital capacity of the lungs

For a quantitative description, the total lung capacity is divided into several components (volumes), i.e. lung capacity is a collection of two or more volumes. Lung volumes are divided into static and dynamic. Static are measured during completed respiratory movements without limiting their speed. Dynamic volumes are measured when performing respiratory movements with a temporary restriction on their implementation.

Vital capacity (VC) includes: tidal volume, expiratory reserve volume, and inspiratory reserve volume. Depending on gender (male or female), age and lifestyle (sports, bad habits), the norm varies from 3 to 5 (or more) liters.

Depending on the method of determination, there is:

Inhalation VC - at the end of a full exhalation, a maximum deep breath is taken.
Expiratory VC - at the end of inhalation, maximum exhalation is carried out.

Tidal volume (TO, TV) - the volume of air inhaled and exhaled by a person during quiet breathing. The value of the tidal volume depends on the conditions under which measurements are performed (at rest, after exercise, body position), sex and age. The average is 500 ml. It is calculated as an average after measuring six even, normal for a given person, respiratory movements.

Inspiratory reserve volume (IRV, IRV) is the maximum amount of air that can be inhaled by a person after his usual breath. The average value is from 1.5 to 1.8 liters.

Expiratory reserve volume (ERV) is the maximum volume of air that can be exhaled additionally by making your normal exhalation. The size of this indicator is smaller in a horizontal position than in a vertical one. Also, expiratory RO decreases with obesity. On average, it is from 1 to 1.4 liters.

What is spirometry - indications and diagnostic procedure

Examination of the function of external respiration

Determination of indicators of static and dynamic lung volumes is possible when conducting a study of the function of external respiration.

Static lung volumes: tidal volume (TO, TV); expiratory reserve volume (RO vyd, ERV); inspiratory reserve volume (RO vd, IRV); vital capacity of the lungs (VC, VC); residual volume (C, RV), total lung capacity (TLC, TLC); airway volume ("dead space", MT on average 150 ml); functional residual capacity (FRC, FRC).

Dynamic lung volumes: forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), Tiffno index (FEV1 / FVC ratio, expressed as a percentage), maximum lung ventilation (MVL). The indicators are expressed as a percentage of the values determined individually for each patient, taking into account his anthropometric data.

The most common method for studying the respiratory function is considered to be the method, which is based on the recording of the flow-volume curve during the implementation of enhanced exhalation of the vital capacity of the lungs (FVC). The capabilities of modern instruments make it possible to compare several curves; based on this comparison, it is possible to determine the correctness of the study. The correspondence of the curves or their close location indicates the correct performance of the study and well-reproducible indicators. When performing enhanced exhalation is done from the position of maximum inspiration. In children, unlike the study technique in adults, the expiration time is not set. Forced exhalation is a functional load on the respiratory system, therefore, between attempts, you should take breaks of at least 3 minutes. But even under these conditions, there may be obstruction from spirometry, a phenomenon in which, with each subsequent attempt, there is a decrease in the area under the curve and a decrease in the recorded indicators.

The unit of measurement of the obtained indicators is a percentage of the due value. Evaluation of the data of the flow-volume curve makes it possible to find possible violations of bronchial conduction, assess the severity and extent of the detected changes, determine at what level changes in the bronchi or violations of their patency are noted. This method allows to detect lesions of small or large bronchi or their joint (generalized) disorders. Diagnosis of patency disorders is performed based on the assessment of FVC and FEV1 and indicators characterizing the speed of air flow through the bronchi (maximum high-speed flows in areas of 25.50 and 75% FVC, peak expiratory flow).

Difficulties during the examination are presented by the age group - children aged 1 to 4 years, due to the peculiarities of the technical part of the study - the performance of respiratory maneuvers. Based on this fact, the assessment of the functioning of the respiratory system in this category of patients is based on an analysis of clinical manifestations, complaints and symptoms, an assessment of the results of the analysis of the gas composition and CBS, arterialized blood. Due to the presence of these difficulties, in recent years, methods based on the study of quiet breathing have been developed and are actively used: bronchophonography, pulse oscillometry. These methods are intended mainly for the evaluation and diagnosis of the patency of the bronchial tree.

Test with a bronchodilator

When deciding whether to make a diagnosis of "bronchial asthma" or clarify the severity of the condition, a test (test) with a bronchodilator is performed. For carrying out, short-acting β2 agonists (Ventolin, Salbutamol) or anticholinergic drugs (Ipratropium bromide, Atrovent) are usually used in age dosages.

If the test is planned for a patient who receives bronchodilators as part of the basic therapy, for proper preparation for the study, they should be canceled before the start of the study. Short-acting B2-agonists, anticholinergic drugs are canceled within 6 hours; long-acting β2-agonists are canceled per day. If the patient is hospitalized for emergency indications and bronchodilators have already been used at the stage of pre-hospital care, the protocol must note which drug was used in the study. Carrying out a test while taking these drugs can "deceive" a specialist and lead to an incorrect interpretation of the results. Before conducting a test with a bronchodilator for the first time, it is necessary to clarify the presence of contraindications to the use of these groups of drugs in a patient.

The algorithm for conducting a sample (test) with a bronchodilator:

a study of the function of external respiration is performed;
inhalation with a bronchodilator is carried out;
re-examination of the function of external respiration (the dosage and the time interval after inhalation to measure the bronchodilatory response depend on the drug chosen).

At the moment, there are different approaches to the methodology for evaluating the results of a test with a bronchodilator. The most widely used assessment of the result is an unconditional increase in the FEV1 indicator. This is explained by the fact that when studying the characteristics of the flow-volume curve, this indicator turned out to have the best reproducibility. An increase in FEV1 by more than 15% of the initial values is conditionally characterized as the presence of reversible obstruction. Normalization of FEV1 in the test with bronchodilators in patients with chronic obstructive pulmonary disease (COPD) occurs in rare cases. A negative result in the test with a bronchodilator (an increase of less than 15%) does not negate the possibility of an increase in FEV1 by a large amount during long-term adequate drug therapy. After a single test with β2-agonists, a third of patients with COPD showed a significant increase in FEV1, in other groups of patients this phenomenon can be observed after several tests.

Peakflowmetry

This is the measurement of peak expiratory flow (PEF, PEF) using portable devices at home in order to monitor the patient's condition with bronchial asthma.

For the study, the patient needs to inhale the maximum possible volume of air. Next, the maximum possible exhalation into the mouthpiece of the device is performed. Usually three measurements are taken in a row. For registration, the measurement with the best result of the three is selected.

The limits of the norm of peak flowmetry indicators depend on the sex, height and age of the subject. Recording of indicators is carried out in the form of a diary (graph or table) of peak flow measurements. Twice a day (morning / evening), the indicators are entered in the diary as a point corresponding to the best of three attempts. Then these points are connected by straight lines. Under the graph, a special field (column) for notes should be allocated. They indicate the medications taken over the past day, and factors that could affect the person's condition: weather changes, stress, the addition of a viral infection, contact with a large amount of a causally significant allergen. Regular filling in the diary will help to identify in a timely manner what caused the deterioration of well-being and evaluate the effect of drugs.

Bronchial patency has its own daily fluctuations. In healthy people, fluctuations in PSV should not be more than 15% of the norm. In people with asthma, fluctuations during the day during the period of remission should not be more than 20%.

The system of zones on the peak flow meter is based on the principle of a traffic light: green, yellow, red:

Green zone - if the PSV values are within this zone, they talk about clinical or pharmacological (if the patient uses drugs) remission. In this case, the patient continues the drug therapy regimen prescribed by the doctor and leads his usual lifestyle.
The yellow zone is a warning about the beginning of a possible deterioration in the condition. When lowering PSV values within the boundaries of the yellow zone, it is necessary to analyze the diary data and consult a doctor. The main task in this situation is to return the indicators to the values in the green zone.
The red zone is a danger signal. You need to contact your doctor immediately. There may be a need for urgent action.

Adequate control over the condition allows you to gradually reduce the amount of drug therapy used, leaving only the most necessary drugs in minimal dosages. The use of a traffic light system will allow timely detection of health-threatening disorders and help prevent unplanned hospitalization.

VITAL CAPACITY OF THE LUNGS.

VC in each person in the process of its development undergoes significant changes: first it increases, and then (in the elderly) decreases. To quantify lung ventilation, it is necessary to know the components of VC. Lung volumes are divided into static and dynamic. Static lung volumes are measured with completed respiratory movements without limiting their speed. Dynamic lung volumes are measured during respiratory movements with a time limit for their implementation. VC is the volume of air that can be exhaled as much as possible after a maximum inhalation. Middle-aged people have an average of 3.5-5.0 liters.

The total lung capacity (TLC) consists of VC and residual air (about 1.0-1.5 l). VC consists of: 1) respiratory air (volume) » 500 ml (from 400 to 900 ml there may be individual fluctuations that depend on age, gender, physical fitness). Out of 500 ml, 350-360 ml reaches the lungs, and 140-150 ml remains in the dead space - in the airways; 2) inspiratory reserve volume - the volume of air that can be inhaled at maximum inspiration after a normal inspiration. On average, 1.5-1.8 liters; 3) expiratory reserve volume - the volume of air that can be exhaled at maximum exhalation after a quiet exhalation. Equal to 1.0-1.4 liters.

Residual volume - equal to 1-1.5 liters, it is not included in the VC - this is the volume of air that remains in the lungs after maximum exhalation. It can come out with bilateral pneumothorax, when opening the chest. To determine the residual volume, inert gases are used, the concentration of the inhaled inert gas and the final inert gas in the exhaled air is taken into account, and the residual volume is determined by the calculation method.

Functional residual capacity (FRC) is the sum of residual air and expiratory reserve volume. On average, 2.8-3.0 liters. One-time ventilation occurs from this part of the air - 350 ml of air enters in one breath and exhalation. The ventilation coefficient is 1/6-1/7 of this volume.

Factors affecting VC:

1) age: in children, VC is less than in adults. Older people have less than middle-aged people. Due VC (JEL) is determined by the Baldwin formula (you will determine it in practical exercises). If there is a difference of up to 15% between JEL and ZHEL, then this is normal;

2) the degree of physical fitness (athletes have more VC). This is due to the great force of contraction of the respiratory muscles and the elastic properties of the lungs;

3) gender (for women "25% less than for men);

4) in diseases of the respiratory system (with emphysema, with inflammation of the lungs, VC decreases). Measurement of lung volumes is performed by spirometry and spirography. The determination of these values has clinical (in patients) and control (in healthy people, athletes) significance.

Anatomical harmful space(150-160 ml) - includes all airways. There is no exchange of gases between the blood and the respiratory tract. With an increase in the harmful space (for example, in a gas mask), less air reaches the lungs at a normal inhalation depth, so breathing should be deep, and moisture accumulates under the gas mask, which leads to a decrease in the partial pressure of oxygen. In addition to the concept of anatomical harmful (dead) space, there is the concept of functional (physiological) harmful space. This, in addition to the airways, includes non-functioning alveoli. This indicator is variable. It changes due to the fact that blood flow stops through the capillaries of some alveoli, they do not participate in gas exchange, and the functional harmful space increases.

LUNG VENTILATION.

The exchange of O 2 and CO 2 between atmospheric air and the internal environment of the body is facilitated by the constant renewal of the composition of the air in the alveoli, i.e. alveolar ventilation occurs. The degree of pulmonary ventilation depends on the depth and frequency of breathing. With an increase in the volume of respiratory air (and during intense muscular work it can increase up to 2500 ml, i.e. 5 times), the ventilation of the lungs and alveoli increases sharply. To quantify the degree of ventilation of the lungs, there are concepts: minute respiratory volume (MOD), minute ventilation of the lungs and single ventilation of the lungs. Minute respiratory volume is the total amount of air that passes through the lungs in 1 minute. At rest, this volume is 6-8 liters. A simple method for determining the MOD is to multiply the respiratory rate by the tidal volume (for example, 16 500). With intensive muscular work, the minute volume of breathing can reach up to 100-120 l.

One-time ventilation of the lungs is understood as the volume of air that is updated with each inhalation and exhalation, i.e. is about 350-360 ml (tidal volume minus the volume of the harmful space). As a result of lung ventilation, the level of partial pressure of gases in the alveoli is at a fairly constant level. The composition of atmospheric air in terms of the percentage of gases differs significantly from the alveolar and exhaled air. Atmospheric air contains: O 2 - 20.85%, CO 2 - 0.03-0.04%, nitrogen - 78.62%. The alveolar air contains O 2 - 13.5%, CO 2 - 5.3% and nitrogen - 74.9%. In the exhaled air, the content of these gases is 15.5%, 3.7% and 74.6%, respectively. The percentages of gases given above are fairly stable, but their partial pressures may vary depending on the total barometric pressure. The partial pressure of gases decreases in high altitude conditions. From the above data it is also seen that the oxygen content in the exhaled air is greater than in the alveolar air, and less carbon dioxide. This is due to the fact that the exhaled air, passing through the respiratory tract, is mixed with the air contained in them, and the composition of the air in the upper respiratory tract is close to the composition of atmospheric air. An important indicator of the effectiveness of breathing is alveolar ventilation, it is the degree of alveolar ventilation that determines the supply of oxygen to the body and the removal of carbon dioxide. The minute volume of respiration does not always reflect the true exchange of gases between the alveoli and the blood. It can be sufficiently increased even when breathing is frequent and shallow, but in this case, alveolar ventilation will be less pronounced than with deep breathing. The nature of lung ventilation can change as a result of the influence of various reasons: muscular work, psycho-emotional arousal, low partial pressure of oxygen or high CO 2 content, various pathological processes in the respiratory and cardiovascular systems, etc. Recently, an attempt has been made to classify the types of ventilation.

The following types of ventilation have been identified:

1) normal ventilation, when the partial pressure of CO 2 in the alveoli is about 40 mm Hg;

2) hyperventilation, when the partial pressure of CO 2 in the alveoli is below 40 mm Hg;

3) hypoventilation when pars. pressure CO 2 in the alveoli is above 40 mm Hg;

4) increased ventilation - any increase in alveolar ventilation compared to the level of rest, regardless of the partial pressure of gases in the alveoli (for example, during muscle work);

5) eupnea - normal ventilation at rest with a feeling of comfort;

6) hyperpnea - an increase in the depth of breathing, regardless of whether the respiratory rate is changed or not;

7) tachypnea - an increase in the frequency of breathing;

8) bradypnea - decrease in respiratory rate;

9) apnea - respiratory arrest (due to a decrease in the partial pressure of CO 2 in arterial blood;

10) dyspnea (shortness of breath) - an unpleasant subjective feeling of insufficiency of breathing or difficulty in breathing;

11) orthopnea - severe shortness of breath due to stagnation (most often) of blood in the pulmonary capillaries as a result of left ventricular failure. It is difficult for such patients to lie down;

12) asphyxia - respiratory arrest or depression (most often with paralysis of the respiratory center).

Artificial respiration. Stopping breathing, regardless of the cause that caused it, is deadly. From the moment of stopping breathing and blood circulation, a person is in a state of clinical death. As a rule, already after 5-10 minutes, the lack of O 2 and the accumulation of CO 2 lead to irreversible damage to the cells of vital organs, resulting in biological death. If resuscitation measures are carried out within this short period, then a person can be saved.

Respiratory failure can be caused by a variety of causes, including blockage of the airways, damage to the chest, severe disruption of gas exchange, and depression of the respiratory centers due to brain damage or poisoning. For some time after a sudden stop of breathing, blood circulation is still preserved: the pulse on the carotid artery is determined within 3-5 minutes after the last breath. In the case of sudden cardiac arrest, respiratory movements stop after 30-60 seconds.

Ensuring airway patency. In an unconscious person, protective reflexes are lost, due to which the airways are normally free. Under these conditions, vomiting or bleeding from the nose or throat can lead to blockage of the airways (trachea and bronchi). Therefore, to restore breathing, first of all, it is necessary to quickly clear the mouth and throat. However, even without these complications, the airways of an unconscious person on their back can be blocked by the tongue as a result of the retraction of the lower jaw. To prevent the overlapping of the airways with the tongue, the patient's head is thrown back and his lower jaw is displaced anteriorly.

Artificial respiration by inhalation. For artificial respiration without the help of special devices, the most effective method is when the resuscitator blows air into the nose or mouth of the victim, i.e. directly into his respiratory tract.

When breathing "mouth to nose", the resuscitator puts his hand on the victim's forehead in the area of \u200b\u200bthe border of hair growth and throws his head back. With the second hand, the resuscitator pushes the lower jaw of the victim and closes his mouth, pressing his thumb on his lips. After taking a deep breath, the resuscitator tightly presses his mouth to the nose of the victim and insufflates (blowing air into the airways). In this case, the chest of the victim should rise. Then the resuscitator releases the nose of the victim, and passive exhalation occurs under the action of the gravity of the chest and the elastic recoil of the lungs. In this case, you should ensure that the chest returns to its original position.

When breathing “mouth to mouth”, the resuscitator and the victim occupy the same position: one palm of the resuscitator lies on the patient’s forehead, the other under his lower jaw, the resuscitator presses his mouth to the victim’s mouth, while covering his nose with his cheek. You can also squeeze the victim's nostrils with the thumb and forefinger of the hand lying on the forehead. With this method of artificial respiration, one should also monitor the movements of the chest during insufflation and exhalation.

Whatever method of artificial respiration is used, first of all, it is necessary to produce 5-10 insufflations at a fast pace in order to eliminate the lack of O 2 and excess CO 2 in the tissues as quickly as possible. After this, insufflation should be performed at intervals of 5 s. Subject to these rules, the saturation of the arterial blood of the victim with oxygen almost constantly exceeds 90%.

Artificial respiration with special devices. There is a simple device with which (if it is at hand) you can perform artificial respiration. It consists of a mask tightly applied to the patient's face, a valve and a bag that is manually compressed and then straightened out. If an oxygen cylinder is available, it can be connected to this device in order to increase the O 2 content of the inhaled air.

With currently widely used inhalation anesthesia, air from the respiratory apparatus enters the lungs through the endotracheal tube. In this case, it is possible to supply air to the lungs at an increased pressure, and then the inhalation will occur as a result of the inflation of the lungs, and the exhalation will be passive. It is also possible to control breathing by creating fluctuations in pressure so that it is alternately above and below atmospheric pressure (while the average pressure should be equal to atmospheric pressure). Since negative pressure in the chest cavity promotes the return of venous blood to the heart, it is preferable to apply artificial respiration in the mode of changing pressure.

The use of breathing pumps or manual breathing bags is necessary during operations using muscle relaxants that eliminate reflex muscle tension. These substances “turn off” the respiratory muscles, so ventilation of the lungs is possible only through artificial respiration.

If the patient has a chronic disorder of external respiration (for example, with children's spinal paralysis), ventilation of the lungs can be maintained using the so-called boxed respirator ("iron lung"). In this case, the patient's torso, which is in a horizontal position, is placed in the chamber, leaving only the head free. To initiate inspiration, the pressure in the chamber is lowered so that the intrathoracic pressure becomes higher than the pressure in the external environment.