Reserve air in the lungs. Lung studies

Tidal volume (TV) is the volume of air inhaled and exhaled during normal breathing, equal to an average of 500 ml (with fluctuations from 300 to 900 ml).

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

Expiratory reserve volume

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

Inspiratory reserve volume

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

Vital capacity of the lungs

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

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

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

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

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

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

VC=2.5*height (m)

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

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

Residual volume

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

Total lung capacity

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

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

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

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

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

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

During inhalation, the lungs are filled with a certain amount of air. This value is not constant and may change under different circumstances. The volume depends on external and internal factors.

What affects lung capacity?

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

Systematic smoking reduces lung capacity. Low filling capacity is typical for hypersthenics (short people with a rounded body and short, wide-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 thin, low-density air.

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 and puts pressure on the diaphragm. This does not affect the woman’s general condition, since compensatory mechanisms are activated. Due to accelerated ventilation, they prevent the development of hypoxia.

Average lung volumes

Lung volume is measured in liters. Average values are calculated during normal breathing at rest, without deep inhalations and full exhalations.

The average figure is 3-4 liters. In physically developed men, the volume during moderate breathing can reach up to 6 liters. The normal number of respiratory acts is 16-20. With active physical activity and nervous strain, these numbers increase.

Vital capacity, or vital capacity of the lungs

The vital capacity is the greatest capacity of the lung during maximum inhalation and exhalation. In young, healthy men, the figure 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.

Taking into account the phases of lung ventilation, the following types of volume are divided:

respiratory - air that circulates freely through the bronchopulmonary system at rest;
reserve during inhalation - air filled with the organ during maximum inhalation after a quiet exhalation;
exhalation reserve - the amount of air removed from the lungs during a sharp exhalation after a calm inhalation;
residual - air remaining in the chest after maximum exhalation.

Airway ventilation refers to gas exchange for 1 minute.

The formula for determining it is:

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

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

Table of indicators of the average lung volume:

The air that is located 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”, which is 150-200 cm 3 .

Vital capacity measurement method

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

Spirometry is prescribed to patients with respiratory dysfunction and chronic bronchopulmonary diseases. Calm and forced breathing are assessed, and functional tests are performed with bronchodilators.

Digital data of vital fluid during spirography are distinguished by age, gender, anthropometric data, and the absence or presence of chronic diseases.

Formulas for calculating individual vital capacity, 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 a height of up to 165 cm – 4.53×P – 3.9; with height over 165 cm – 10×P – 12.85;
for girls from 4 to 17 years old the swarm grows from 100 to 175 cm - 3.75×P - 3.15.

Measurement of vital capacity is not carried out for children under 4 years of age, patients with mental disorders, or with maxillofacial injuries. An absolute contraindication is acute contagious infection.

Diagnostics are not prescribed if it is physically impossible to carry out the 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 vital capacity indicators

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

Respiratory function is considered impaired if a person’s lung capacity is less than 80%. This is the first signal of insufficiency of the bronchopulmonary system.

External signs of pathology:

breathing problems during active movements;

change in chest amplitude.

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 cases of pulmonary emphysema and bronchial asthma. During the course of the disease, swelling of the lungs is formed. Therefore, for diagnostic purposes, percussion is performed (low position of the diaphragm, specific “boxy” sound), chest x-ray (more transparent lung fields, expansion of boundaries).

Factors reducing vital capacity:

reduction in the volume of the pleural cavity due to the development of the cor pulmonale;
rigidity of the organ parenchyma (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 layers);
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 an organ).

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

2. Spirometry. Method for measuring tidal volumes and capacities. The following tidal volumes are distinguished:

Tidal volume – the volume of air that a person inhales and exhales under conditions of relative physiological rest. Normally, this figure in a healthy person can range from 0.4 to 0.5 liters;

Inspiratory reserve volume – the maximum volume of air that a person can inhale additionally after a quiet breath. The inspiratory reserve volume is 1.5 – 1.8 liters.

Expiratory reserve volume – the maximum volume of air that a person can additionally exhale after a quiet exhalation. Normally, this value can be 1.0 – 1.4 liters;

Residual volume – the volume of air that remains in the lungs after maximum exhalation. In a healthy person, this value is 1.0 – 1.5 liters.

To characterize the function of external respiration, they often resort to calculation breathing containers, which consist of the sum of certain tidal volumes:

Vital capacity of the lungs (VC)– consists of the sum of tidal volume, inspiratory reserve volume and expiratory reserve volume. Normally it ranges from 3 to 5 liters. In men, as a rule, this figure is higher than in women.

Inspiratory capacity– equal to the sum of tidal volume and inspiratory reserve volume. In humans, the average is 2.0 – 2.3 liters.

Functional residual capacity (FRC)– the sum of expiratory reserve volume and residual volume. This indicator can be calculated by gas dilution methods using closed-type spirographs. To determine FRC, the inert gas helium is used, which is included in the breathing mixture.

VspXWITHhe 1 = Vsp xWITHhe 2 + FOE x Che 2, Where

Vsp – spirograph volume ; WITHhe 1 – helium concentration in the breathing mixture of the spirograph before the start of the test; WITHhe 2– helium concentration in the breathing mixture during the test. From here

FRC = (Vsp(WITHhe 1-WITHhe 2)/WITHhe 2 ;

Total lung capacity– the sum of all tidal volumes.

Spirometry is carried out using special devices - spirometers. There are dry and wet spirometers. In the practical lesson, we will estimate tidal volumes using various spirometer options.

3. Spirography – a method that allows you to record a respiratory curve, spirogram, and then, through special measurements and calculations, estimate tidal volumes and capacities (see Fig. 5).

Rice. 5 Spirogram and tidal volumes and capacities. Designations: DO – tidal volume; ROV – inspiratory reserve volume; ROvyd. - expiratory reserve volume; Vital capacity – vital capacity of the lungs.

5. Pneumotachometry. Method for estimating air flow speed. The so-called Fleisch tube is used as a sensor, which is connected to a recording device. This indicator is used to assess the condition of the respiratory muscles.

6. Oxygemometry and oxygemography. The method is used to assess the degree of oxygen saturation in the blood. When the blood is saturated with oxygen, it acquires a bright scarlet color and is highly permeable to light flux. Venous blood, saturated with carbon dioxide, is dark in color and poorly permeable to light rays. The oximeter contains a photosensitive element and a light source, which are built into a special clip and fixed to the auricle. The light signal is converted into an electric current, the amplitude of which corresponds to the intensity of the light flux passing through the tissue of the auricle. Next, the signal is amplified and converted into a number, which shows the degree of oxygen saturation in the blood.

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

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

The function of breathing in humans is realized by:

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

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

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

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

Lung capacity

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

Total capacity = Vital capacity + Residual volume

Vital capacity makes up three lung volumes:

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

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

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

functional residual capacity = Expiratory reserve volume + Residual volume

Fig.8.1. Lung volumes and capacities.

Lung volumes and capacities

During the process of pulmonary ventilation, the gas composition of the alveolar air is continuously updated. The amount of pulmonary ventilation is determined by the depth of breathing, or tidal volume, and the frequency of respiratory movements. During breathing movements, a person’s lungs are filled with inhaled air, the volume of which is part of the total volume of the lungs. To quantitatively describe pulmonary ventilation, total lung capacity was divided into several components or volumes. In this case, the pulmonary capacity is the sum of two or more volumes.

Lung volumes are divided into static and dynamic. Static pulmonary volumes are measured during completed respiratory movements without limiting their speed. Dynamic pulmonary volumes are measured during respiratory movements with a time limit for their implementation.

Lung volumes. The volume of air in the lungs and respiratory tract depends on the following indicators: 1) anthropometric individual characteristics of the person and the respiratory system; 2) properties of lung tissue; 3) surface tension of the alveoli; 4) the force developed by the respiratory muscles.

Tidal volume (TO)- the volume of air that a person inhales and exhales during quiet breathing. In an adult, DO is approximately 500 ml. The value of DO depends on the measurement conditions (rest, load, body position). DO is calculated as the average value after measuring approximately six quiet breathing movements.

Inspiratory reserve volume (IRV)- the maximum volume of air that the subject is able to inhale after a quiet breath. The size of the ROVD is 1.5-1.8 liters.

Expiratory reserve volume (ERV)- the maximum volume of air that a person can additionally exhale from the level of quiet exhalation. The value of ROvyd is lower in a horizontal position than in a vertical position, and decreases with obesity. It is equal to an average of 1.0-1.4 liters.

Residual volume (VR)- the volume of air that remains in the lungs after maximum exhalation. The residual volume is 1.0-1.5 liters.

The study of dynamic lung volumes is of scientific and clinical interest, and their description goes beyond the scope of a normal physiology course.

Lung capacity. Vital capacity of the lungs (VC) includes tidal volume, inspiratory reserve volume, and expiratory reserve volume. In middle-aged men, vital capacity varies between 3.5-5.0 liters and more. For women, lower values are typical (3.0-4.0 l). Depending on the methodology for measuring vital capacity, a distinction is made between inhalation vital capacity, when after a complete exhalation a maximum deep breath is taken, and exhalation vital capacity, when after a full inhalation a maximum exhalation is made.

Inspiratory capacity (EIC) is equal to the sum of tidal volume and inspiratory reserve volume. In humans, EUD averages 2.0-2.3 liters.

Functional residual capacity (FRC) is the volume of air in the lungs after a quiet exhalation. FRC is the sum of expiratory reserve volume and residual volume. FRC is measured by gas dilution, or gas dilution, and plethysmography. The value of FRC is significantly influenced by the level of physical activity of a person and body position: FRC is smaller in a horizontal position of the body than in a sitting or standing position. FRC decreases in obesity due to a decrease in the overall compliance of the chest.

Total lung capacity (TLC) is the volume of air in the lungs at the end of a full inhalation. TEL is calculated in two ways: TEL - OO + VC or TEL - FRC + Evd. TLC can be measured using plethysmography or gas dilution.

Measurement of lung volumes and capacities is of clinical importance in the study of pulmonary function in healthy individuals and in the diagnosis of human lung disease. Measurement of lung volumes and capacities is usually carried out using spirometry, pneumotachometry with the integration of indicators, and body plethysmography. Static lung volumes may decrease under pathological conditions that lead to limited lung expansion. These include neuromuscular diseases, diseases of the chest, abdomen, pleural lesions that increase the rigidity of the lung tissue, and diseases that cause a decrease in the number of functioning alveoli (atelectasis, resection, scar changes in the lungs).

For comparability of the results of measurements of gas volumes and capacities, the data obtained must be correlated with the conditions in the lungs, where the temperature of the alveolar air corresponds to body temperature, the air is at a certain pressure and is saturated with water vapor. This state is called standard and is designated by the letters BTPS (body temperature, pressure, saturated).