Indicators of external respiration. Breathing phases
For a freediver, the lungs are the main “working tool” (after the brain, of course), so it is important for us to understand the structure of the lungs and the entire breathing process. Usually, when we talk about breathing, we mean external breathing or ventilation of the lungs - the only process noticeable to us in the respiratory chain. And we must begin to consider breathing with it.
Structure of the lungs and chest
The lungs are a porous organ, similar to a sponge, reminiscent in its structure of a cluster of individual bubbles or a bunch of grapes with a large number of berries. Each “berry” is a pulmonary alveolus (pulmonary vesicle) - the place where the main function of the lungs - gas exchange - occurs. Between the air of the alveoli and the blood lies an air-blood barrier formed by the very thin walls of the alveoli and the blood capillary. It is through this barrier that diffusion of gases occurs: oxygen enters the blood from the alveoli, and carbon dioxide enters the alveoli from the blood.
Air enters the alveoli through the airways - the trochea, bronchi and smaller bronchioles, which end in the alveolar sacs. The branching of the bronchi and bronchioles forms the lobes (the right lung has 3 lobes, the left lung has 2 lobes). On average, there are about 500-700 million alveoli in both lungs, the respiratory surface of which ranges from 40 m2 when exhaling to 120 m2 when inhaling. In this case, a larger number of alveoli are located in the lower parts of the lungs.
The bronchi and trachea have a cartilaginous base in their walls and are therefore quite rigid. Bronchioles and alveoli have soft walls and therefore can collapse, that is, stick together, like a deflated balloon, if a certain air pressure is not maintained in them. To prevent this from happening, the lungs are like a single organ, covered on all sides with pleura - a strong, hermetically sealed membrane.
The pleura has two layers - two leaves. One leaf is tightly adjacent to the inner surface of the hard chest, the other surrounds the lungs. Between them there is a pleural cavity in which negative pressure is maintained. Thanks to this, the lungs are in a straightened state. Negative pressure in the pleural fissure is caused by elastic traction of the lungs, that is, the constant desire of the lungs to reduce their volume.
Elastic traction of the lungs is caused by three factors:
1) the elasticity of the tissue of the walls of the alveoli due to the presence of elastic fibers in them
2) tone of the bronchial muscles
3) surface tension of the liquid film covering the inner surface of the alveoli.
The rigid frame of the chest is made up of the ribs, which are flexible, thanks to cartilage and joints, attached to the spine and joints. Thanks to this, the chest increases and decreases its volume, while maintaining the rigidity necessary to protect the organs located in the chest cavity.
In order to inhale air, we need to create a pressure in the lungs lower than atmospheric, and in order to exhale it is higher. Thus, for inhalation it is necessary to increase the volume of the chest, for exhalation - a decrease in volume. In fact, most of the breathing effort is spent on inhalation; under normal conditions, exhalation is carried out due to the elastic properties of the lungs.
The main respiratory muscle is the diaphragm - a dome-shaped muscular partition between the chest cavity and the abdominal cavity. Conventionally, its border can be drawn along the lower edge of the ribs.
When inhaling, the diaphragm contracts, actively stretching towards the lower internal organs. In this case, the incompressible organs of the abdominal cavity are pushed down and to the sides, stretching the walls of the abdominal cavity. During a quiet inhalation, the dome of the diaphragm descends approximately 1.5 cm, and the vertical size of the thoracic cavity increases accordingly. At the same time, the lower ribs diverge somewhat, increasing the girth of the chest, which is especially noticeable in the lower sections. When you exhale, the diaphragm passively relaxes and is pulled up by the tendons holding it into its calm state.
In addition to the diaphragm, the external oblique intercostal and interchondral muscles also take part in increasing the volume of the chest. As a result of the rise of the ribs, the sternum moves forward and the lateral parts of the ribs move to the sides.
With very deep, intense breathing or when inhalation resistance increases, a number of auxiliary respiratory muscles are included in the process of increasing the volume of the chest, which can raise the ribs: scalenes, pectoralis major and minor, and serratus anterior. The auxiliary muscles of inhalation also include the muscles that extend the thoracic spine and fix the shoulder girdle when supported by arms folded back (trapezius, rhomboid, levator scapula).
As mentioned above, a calm inhalation occurs passively, almost against the background of relaxation of the inspiratory muscles. With active intense exhalation, the muscles of the abdominal wall “connect”, as a result of which the volume of the abdominal cavity decreases and the pressure in it increases. Pressure is transferred to the diaphragm and raises it. Due to the reduction The internal oblique intercostal muscles lower the ribs and bring their edges closer together.
Breathing movements
In ordinary life, after observing yourself and your friends, you can see both breathing, provided mainly by the diaphragm, and breathing, provided mainly by the work of the intercostal muscles. And this is within normal limits. The muscles of the shoulder girdle are more often involved in cases of serious illness or intense work, but almost never in relatively healthy people in normal condition.
It is believed that breathing, provided mainly by movements of the diaphragm, is more characteristic of men. Normally, inhalation is accompanied by a slight protrusion of the abdominal wall, and exhalation is accompanied by a slight retraction. This is the abdominal type of breathing.
In women, the most common type of breathing is the thoracic type, which is provided mainly by the work of the intercostal muscles. This may be due to the woman’s biological readiness for motherhood and, as a consequence, difficulty in abdominal breathing during pregnancy. With this type of breathing, the most noticeable movements are made by the sternum and ribs.
Breathing, in which the shoulders and collarbones actively move, is ensured by the work of the muscles of the shoulder girdle. Ventilation of the lungs is ineffective and only affects the apices of the lungs. Therefore, this type of breathing is called apical. Under normal conditions, this type of breathing practically does not occur and is used either during certain gymnastics or develops in serious diseases.
In freediving, we believe that abdominal breathing or belly breathing is the most natural and productive. The same is said when practicing yoga and pranayama.
Firstly, because there are more alveoli in the lower lobes of the lungs. Secondly, breathing movements are associated with our autonomic nervous system. Belly breathing activates the parasympathetic nervous system - the body's brake pedal. Chest breathing activates the sympathetic nervous system - the gas pedal. With active and prolonged apical breathing, overstimulation of the sympathetic nervous system occurs. It works both ways. This is how panicking people always breathe with apical breathing. Conversely, if you breathe calmly with your stomach for some time, the nervous system calms down and all processes slow down.
Lung volumes
During quiet breathing, a person inhales and exhales about 500 ml (from 300 to 800 ml) of air, this volume of air is called tidal volume. In addition to the normal tidal volume, with the deepest possible inspiration, a person can inhale approximately 3000 ml of air - this is inspiratory reserve volume. After a normal calm exhalation, an ordinary healthy person, by tensing the exhalation muscles, is able to “squeeze” about 1300 more ml of air from the lungs - this expiratory reserve volume.
The sum of these volumes is vital capacity of the lungs (VC): 500 ml + 3000 ml + 1300 ml = 4800 ml.
As we see, nature has prepared for us an almost tenfold reserve of the ability to “pump” air through the lungs.
Tidal volume is a quantitative expression of the depth of breathing. The vital capacity of the lungs determines the maximum volume of air that can be introduced or removed from the lungs during one inhalation or exhalation. The average vital capacity of the lungs in men is 4000 - 5500 ml, in women - 3000 - 4500 ml. Physical training and various stretches of the chest can increase VC.
After a maximum deep exhalation, about 1200 ml of air remains in the lungs. This - residual volume. Most of it can be removed from the lungs only with an open pneumothorax.
The residual volume is determined primarily by the elasticity of the diaphragm and intercostal muscles. Increasing the mobility of the chest and reducing the residual volume is an important task when preparing for diving to great depths. Dives below the residual volume for an ordinary untrained person are dives deeper than 30-35 meters. One of the popular ways to increase the elasticity of the diaphragm and reduce residual lung volume is to regularly perform uddiyana bandha.
The maximum amount of air that can be held in the lungs is called total lung capacity, it is equal to the sum of the residual volume and vital capacity of the lungs (in the example used: 1200 ml + 4800 ml = 6000 ml).
The volume of air in the lungs at the end of a quiet exhalation (with relaxed respiratory muscles) is called functional residual capacity of the lungs. It is equal to the sum of the residual volume and the expiratory reserve volume (in the example used: 1200 ml + 1300 ml = 2500 ml). The functional residual capacity of the lungs is close to the volume of alveolar air before the onset of inspiration.
Ventilation is determined by the volume of air inhaled or exhaled per unit of time. Usually measured minute volume of respiration. Ventilation of the lungs depends on the depth and frequency of breathing, which at rest ranges from 12 to 18 breaths per minute. The minute volume of breathing is equal to the product of the tidal volume and the respiratory frequency, i.e. approximately 6-9 l.
To assess lung volumes, spirometry is used - a method for studying the function of external respiration, which includes measuring volume and speed parameters of breathing. We recommend this study to anyone planning to take up freediving seriously.
Air is found not only in the alveoli, but also in the airways. These include the nasal cavity (or mouth during oral breathing), nasopharynx, larynx, trachea, and bronchi. The air in the airways (with the exception of the respiratory bronchioles) does not participate in gas exchange. Therefore, the lumen of the airways is called
anatomical dead space. When you inhale, the last portions of atmospheric air enter the dead space and, without changing its composition, leave it when you exhale.
The volume of anatomical dead space is about 150 ml or approximately 1/3 of the tidal volume during quiet breathing. Those. out of 500 ml of inhaled air, only about 350 ml enters the alveoli. At the end of a quiet exhalation, there is about 2500 ml of air in the alveoli, so with each quiet breath, only 1/7 of the alveolar air is renewed.
- < Back
The main methods for studying breathing in humans include:
· Spirometry is a method for determining the vital capacity of the lungs (VC) and its constituent air volumes.
· Spirography is a method of graphically recording indicators of the function of the external part of the respiratory system.
· Pneumotachometry is a method for measuring the maximum speed of inhalation and exhalation during forced breathing.
· Pneumography is a method of recording respiratory movements of the chest.
· Peak fluorometry is a simple way of self-assessment and constant monitoring of bronchial patency. The device - peak flow meter allows you to measure the volume of air passing during exhalation per unit time (peak expiratory flow).
· Functional tests (Stange and Genche).
Spirometry
The functional state of the lungs depends on age, gender, physical development and a number of other factors. The most common characteristic of the condition of the lungs is the measurement of lung volumes, which indicate the development of the respiratory organs and the functional reserves of the respiratory system. The volume of air inhaled and exhaled can be measured using a spirometer.
Spirometry is the most important way to assess respiratory function. This method determines the vital capacity of the lungs, lung volumes, as well as the volumetric air flow rate. During spirometry, a person inhales and exhales as forcefully as possible. The most important data is provided by analysis of the expiratory maneuver - exhalation. Lung volumes and capacities are called static (basic) respiratory parameters. There are 4 primary pulmonary volumes and 4 capacities.
Vital capacity of the lungs
The vital capacity of the lungs is the maximum amount of air that can be exhaled after a maximum inhalation. During the study, the actual vital capacity is determined, which is compared with the expected vital capacity (VC) and calculated using formula (1). In an adult of average height, the BEL is 3-5 liters. In men, its value is approximately 15% greater than in women. Schoolchildren aged 11-12 years have a VAL of about 2 liters; children under 4 years old - 1 liter; newborns - 150 ml.
VIT=DO+ROVD+ROVD, (1)
Where vital capacity is the vital capacity of the lungs; DO - respiratory volume; ROVD - inspiratory reserve volume; ROvyd - expiratory reserve volume.
JEL (l) = 2.5 Chrost (m). (2)
Tidal volume
Tidal volume (TV), or depth of breathing, is the volume of inhaled and
air exhaled at rest. In adults, DO = 400-500 ml, in children 11-12 years old - about 200 ml, in newborns - 20-30 ml.
Expiratory reserve volume
Expiratory reserve volume (ERV) is the maximum volume that can be exhaled with effort after a quiet exhalation. ROvyd = 800-1500 ml.
Inspiratory reserve volume
Inspiratory reserve volume (IRV) is the maximum volume of air that can be additionally inhaled after a quiet inhalation. Inspiratory reserve volume can be determined in two ways: calculated or measured with a spirometer. To calculate, it is necessary to subtract the sum of the respiratory and expiratory reserve volumes from the vital capacity value. To determine the inspiratory reserve volume using a spirometer, you need to fill the spirometer with 4 to 6 liters of air and, after a quiet inhalation from the atmosphere, take a maximum breath from the spirometer. The difference between the initial volume of air in the spirometer and the volume remaining in the spirometer after a deep inspiration corresponds to the inspiratory reserve volume. ROVD =1500-2000 ml.
Residual volume
Residual volume (VR) is the volume of air remaining in the lungs even after maximum exhalation. Measured only by indirect methods. The principle of one of them is that a foreign gas such as helium is injected into the lungs (dilution method) and the volume of the lungs is calculated by changing its concentration. The residual volume is 25-30% of the vital capacity. Take OO=500-1000 ml.
Total lung capacity
Total lung capacity (TLC) is the amount of air in the lungs after maximum inspiration. TEL = 4500-7000 ml. Calculated using formula (3)
OEL=VEL+OO. (3)
Functional residual capacity of the lungs
Functional residual lung capacity (FRC) is the amount of air remaining in the lungs after a quiet exhalation.
Calculated using formula (4)
FOEL=ROVD. (4)
Input capacitance
Inlet capacity (IUC) is the maximum volume of air that can be inhaled after a quiet exhalation. Calculated using formula (5)
EVD=DO+ROVD. (5)
In addition to static indicators that characterize the degree of physical development of the respiratory apparatus, there are additional dynamic indicators that provide information about the effectiveness of lung ventilation and the functional state of the respiratory tract.
Forced vital capacity
Forced vital capacity (FVC) is the amount of air that can be exhaled during a forced exhalation after a maximum inhalation. Normally, the difference between VC and FVC is 100-300 ml. An increase in this difference to 1500 ml or more indicates resistance to air flow due to narrowing of the lumen of the small bronchi. FVC = 3000-7000 ml.
Anatomical dead space
Anatomical dead space (ADS) - the volume in which gas exchange does not occur (nasopharynx, trachea, large bronchi) - cannot be directly determined. DMP = 150 ml.
Respiration rate
Respiratory rate (RR) is the number of respiratory cycles in one minute. BH = 16-18 bpm/min.
Minute breathing volume
Minute respiration volume (MVR) is the amount of air ventilated in the lungs in 1 minute.
MOD = TO + BH. MOD = 8-12 l.
Alveolar ventilation
Alveolar ventilation (AV) is the volume of exhaled air entering the alveoli. AB = 66 - 80% of mod. AB = 0.8 l/min.
Breathing reserve
Breathing reserve (RR) is an indicator characterizing the possibilities of increasing ventilation. Normally, RD is 85% of maximum pulmonary ventilation (MVV). MVL = 70-100 l/min.
Breathing phases.
External respiration process is caused by changes in the volume of air in the lungs during the inhalation and exhalation phases of the respiratory cycle. During quiet breathing, the ratio of the duration of inhalation to exhalation in the respiratory cycle is on average 1:1.3. External breathing of a person is characterized by the frequency and depth of respiratory movements. Respiration rate a person is measured by the number of respiratory cycles within 1 minute and its value at rest in an adult varies from 12 to 20 per 1 minute. This indicator of external respiration increases with physical work, increasing ambient temperature, and also changes with age. For example, in newborns the respiratory rate is 60-70 per 1 min, and in people aged 25-30 years - an average of 16 per 1 min. Breathing depth determined by the volume of inhaled and exhaled air during one respiratory cycle. The product of the frequency of respiratory movements and their depth characterizes the basic value of external respiration - ventilation. A quantitative measure of pulmonary ventilation is the minute volume of breathing - this is the volume of air that a person inhales and exhales in 1 minute. The minute volume of a person's breathing at rest varies between 6-8 liters. During physical work, a person's minute breathing volume can increase 7-10 times.
Rice. 10.5. Volumes and capacities of air in the human lungs and the curve (spirogram) of changes in air volume in the lungs during quiet breathing, deep inhalation and exhalation. FRC - functional residual capacity.
Pulmonary air volumes. IN respiratory physiology a unified nomenclature of pulmonary volumes in humans has been adopted, which fill the lungs during quiet and deep breathing during the inhalation and exhalation phases of the respiratory cycle (Fig. 10.5). The lung volume that is inhaled or exhaled by a person during quiet breathing is called tidal volume. Its value during quiet breathing averages 500 ml. The maximum amount of air that a person can inhale above the tidal volume is called inspiratory reserve volume(average 3000 ml). The maximum amount of air that a person can exhale after a quiet exhalation is called the expiratory reserve volume (on average 1100 ml). Finally, the amount of air that remains in the lungs after maximum exhalation is called the residual volume, its value is approximately 1200 ml.
The sum of two or more pulmonary volumes is called pulmonary capacity. Air volume in human lungs it is characterized by inspiratory lung capacity, vital lung capacity and functional residual lung capacity. Inspiratory capacity (3500 ml) is the sum of tidal volume and inspiratory reserve volume. Vital capacity of the lungs(4600 ml) includes tidal volume and inspiratory and expiratory reserve volumes. Functional residual lung capacity(1600 ml) is the sum of expiratory reserve volume and residual lung volume. Sum vital capacity of the lungs And residual volume is called the total lung capacity, the average value of which in humans is 5700 ml.
When inhaling, the human lungs due to contraction of the diaphragm and external intercostal muscles, they begin to increase their volume from the level, and its value during quiet breathing is tidal volume, and with deep breathing - reaches different values reserve volume inhale. When exhaling, the volume of the lungs returns to the original level of functional function. residual capacity passively, due to elastic traction of the lungs. If air begins to enter the volume of exhaled air functional residual capacity, which occurs during deep breathing, as well as when coughing or sneezing, then exhalation is carried out by contracting the muscles of the abdominal wall. In this case, the value of intrapleural pressure, as a rule, becomes higher than atmospheric pressure, which determines the highest speed of air flow in the respiratory tract.
2. Spirography technique .
The study is carried out in the morning on an empty stomach. Before the study, the patient is recommended to remain calm for 30 minutes, and also stop taking bronchodilators no later than 12 hours before the start of the study.
The spirographic curve and pulmonary ventilation indicators are shown in Fig. 2.
Static indicators(determined during quiet breathing).
The main variables used to display observed indicators of external respiration and to construct construct indicators are: volume of respiratory gas flow, V (l) and time t ©. The relationships between these variables can be presented in the form of graphs or charts. All of them are spirograms.
A graph of the volume of flow of a mixture of respiratory gases versus time is called a spirogram: volume flow - time.
The graph of the relationship between the volumetric flow rate of a mixture of respiratory gases and the flow volume is called a spirogram: volumetric velocity flow - volume flow.
Measure tidal volume(DO) - the average volume of air that the patient inhales and exhales during normal breathing at rest. Normally it is 500-800 ml. The part of sediments that takes part in gas exchange is called alveolar volume(AO) and on average equals 2/3 of the DO value. The remainder (1/3 of the DO value) is functional dead space volume(FMP).
After a calm exhalation, the patient exhales as deeply as possible - measured expiratory reserve volume(ROvyd), which is normally 1000-1500 ml.
After a calm inhalation, the deepest possible breath is taken - measured inspiratory reserve volume(Rovd). When analyzing static indicators, it is calculated inspiratory capacity(Evd) - the sum of DO and Rovd, which characterizes the ability of lung tissue to stretch, as well as vital capacity(VC) - the maximum volume that can be inhaled after the deepest exhalation (the sum of DO, RO VD and Rovyd normally ranges from 3000 to 5000 ml).
After normal quiet breathing, a breathing maneuver is performed: the deepest possible breath is taken, and then the deepest, sharpest and longest (at least 6 s) exhalation is taken. This is how it is determined forced vital capacity(FVC) - the volume of air that can be exhaled during forced exhalation after maximum inspiration (normally 70-80% VC).
As the final stage of the study, recording is carried out maximum ventilation(MVL) - the maximum volume of air that can be ventilated by the lungs in 1 min. MVL characterizes the functional capacity of the external respiration apparatus and is normally 50-180 liters. A decrease in MVL is observed with a decrease in pulmonary volumes due to restrictive (limiting) and obstructive disorders of pulmonary ventilation.
When analyzing the spirographic curve obtained in the maneuver with forced exhalation, measure certain speed indicators (Fig. 3):
1) forced expiratory volume in the first second (FEV 1) - the volume of air that is exhaled in the first second with the fastest possible exhalation; it is measured in ml and calculated as a percentage of FVC; healthy people exhale at least 70% of FVC in the first second;
2) sample or Tiffno index- ratio of FEV 1 (ml)/VC (ml), multiplied by 100%; normally is at least 70-75%;
3) maximum volumetric air velocity at the expiratory level of 75% FVC (MOV 75) remaining in the lungs;
4) maximum volumetric air velocity at the expiratory level of 50% FVC (MOV 50) remaining in the lungs;
5) maximum volumetric air velocity at the expiratory level of 25% FVC (MOV 25) remaining in the lungs;
6) average forced expiratory volumetric flow rate, calculated in the measurement interval from 25 to 75% FVC (SES 25-75).
Symbols on the diagram.
Indicators of maximum forced expiration:
25 ÷ 75% FEV- volumetric flow rate in the average forced expiratory interval (between 25% and 75%
vital capacity of the lungs),
FEV1- flow volume during the first second of forced exhalation.
Rice. 3. Spirographic curve obtained in the forced expiratory maneuver. Calculation of FEV 1 and SOS 25-75 indicators
Calculation of speed indicators is of great importance in identifying signs of bronchial obstruction. A decrease in the Tiffno index and FEV 1 is a characteristic sign of diseases that are accompanied by a decrease in bronchial patency - bronchial asthma, chronic obstructive pulmonary disease, bronchiectasis, etc. MOS indicators are of the greatest value in diagnosing the initial manifestations of bronchial obstruction. SOS 25-75 reflects the state of patency of small bronchi and bronchioles. The latter indicator is more informative than FEV 1 for identifying early obstructive disorders.
Due to the fact that in Ukraine, Europe and the USA there is some difference in the designation of lung volumes, capacities and speed indicators that characterize pulmonary ventilation, we present the designations of these indicators in Russian and English (Table 1).
Table 1. Name of pulmonary ventilation indicators in Russian and English
| Name of the indicator in Russian | Accepted abbreviation | Indicator name in English | Accepted abbreviation |
| Vital capacity of the lungs | vital capacity | Vital capacity | V.C. |
| Tidal volume | TO | Tidal volume | TV |
| Inspiratory reserve volume | Rovd | Inspiratory reserve volume | IRV |
| Expiratory reserve volume | Rovyd | Expiratory reserve volume | ERV |
| Maximum ventilation | MVL | Maximum voluntary ventilation | M.W. |
| Forced vital capacity | FVC | Forced vital capacity | FVC |
| Forced expiratory volume in the first second | FEV1 | Forced expiratory volume 1 sec | FEV1 |
| Tiffno index | IT, or FEV 1/VC% | FEV1% = FEV1/VC% | |
| Maximum flow rate at the moment of exhalation 25% FVC remaining in the lungs | MOS 25 | Maximum expiratory flow 25% FVC | MEF25 |
| Forced expiratory flow 75% FVC | FEF75 | ||
| Maximum flow rate at the moment of exhalation of 50% FVC remaining in the lungs | MOS 50 | Maximum expiratory flow 50% FVC | MEF50 |
| Forced expiratory flow 50% FVC | FEF50 | ||
| Maximum flow rate at the moment of exhalation 75% FVC remaining in the lungs | MOS 75 | Maximum expiratory flow 75% FVC | MEF75 |
| Forced expiratory flow 25% FVC | FEF25 | ||
| Average expiratory volumetric flow rate in the range from 25% to 75% FVC | SOS 25-75 | Maximum expiratory flow 25-75% FVC | MEF25-75 |
| Forced expiratory flow 25-75% FVC | FEF25-75 |
Table 2. Name and correspondence of pulmonary ventilation indicators in different countries
| Ukraine | Europe | USA |
| mos 25 | MEF25 | FEF75 |
| mos 50 | MEF50 | FEF50 |
| mos 75 | MEF75 | FEF25 |
| SOS 25-75 | MEF25-75 | FEF25-75 |
All indicators of pulmonary ventilation are variable. They depend on gender, age, weight, height, body position, the state of the patient’s nervous system and other factors. Therefore, for a correct assessment of the functional state of pulmonary ventilation, the absolute value of one or another indicator is insufficient. It is necessary to compare the obtained absolute indicators with the corresponding values in a healthy person of the same age, height, weight and gender - the so-called proper indicators. This comparison is expressed as a percentage relative to the proper indicator. Deviations exceeding 15-20% of the expected value are considered pathological.
5. SPIROGRAPHY WITH REGISTRATION OF THE FLOW-VOLUME LOOP
Spirography with registration of the flow-volume loop - a modern method of studying pulmonary ventilation, which consists in determining the volumetric speed of air flow in the inhalation tract and graphically displaying it in the form of a flow-volume loop during quiet breathing of the patient and when he performs certain breathing maneuvers. Abroad this method is called spirometry.
Purpose The study is to diagnose the type and degree of pulmonary ventilation disorders based on the analysis of quantitative and qualitative changes in spirographic indicators.
Indications and contraindications for the use of the method are similar to those for classical spirography.
Methodology. The study is carried out in the first half of the day, regardless of food intake. The patient is asked to close both nasal passages with a special clamp, take an individual sterilized mouthpiece into his mouth and tightly clasp his lips around it. The patient, in a sitting position, breathes through the tube in an open circuit, experiencing virtually no breathing resistance
The procedure for performing breathing maneuvers with recording the flow-volume curve of forced breathing is identical to that performed when recording FVC during classical spirography. The patient should be explained that in a test with forced breathing one should exhale into the device as if one were to extinguish the candles on a birthday cake. After a period of quiet breathing, the patient takes a maximally deep breath, resulting in an elliptical curve (AEB curve) being recorded. Then the patient makes the fastest and most intense forced exhalation. In this case, a curve of a characteristic shape is recorded, which in healthy people resembles a triangle (Fig. 4).
Rice. 4. Normal loop (curve) of the relationship between the volumetric flow rate and air volume during breathing maneuvers. Inhalation begins at point A, exhalation begins at point B. POSV is recorded at point C. The maximum expiratory flow in the middle of the FVC corresponds to point D, the maximum inspiratory flow to point E
Spirogram: volumetric flow rate - volume of forced inhalation/exhalation flow.
The maximum expiratory volumetric air flow rate is displayed by the initial part of the curve (point C, where peak expiratory flow rate- POS EXP) - After this, the volumetric flow rate decreases (point D, where MOC 50 is recorded), and the curve returns to its original position (point A). In this case, the flow-volume curve describes the relationship between the volumetric air flow rate and the pulmonary volume (lung capacity) during respiratory movements.
Data on speeds and volumes of air flow are processed by a personal computer thanks to adapted software. The flow-volume curve is displayed on the monitor screen and can be printed on paper, saved on magnetic media or in the memory of a personal computer.
Modern devices work with spirographic sensors in an open system with subsequent integration of the air flow signal to obtain synchronous values of lung volumes. The computer-calculated research results are printed together with the flow-volume curve on paper in absolute values and as a percentage of the required values. In this case, FVC (air volume) is plotted on the abscissa axis, and air flow, measured in liters per second (l/s), is plotted on the ordinate axis (Fig. 5).
Rice. 5. Flow-volume curve of forced breathing and pulmonary ventilation indicators in a healthy person
Rice. 6
Scheme of the FVC spirogram and the corresponding forced expiratory curve in “flow-volume” coordinates: V - volume axis; V" - flow axis
The flow-volume loop is the first derivative of the classical spirogram. Although the flow-volume curve contains essentially the same information as the classic spirogram, the visualization of the relationship between flow and volume allows deeper insight into the functional characteristics of both the upper and lower airways (Fig. 6). Calculation of highly informative indicators MOS 25, MOS 50, MOS 75 using a classical spirogram has a number of technical difficulties when performing graphic images. Therefore, its results are not highly accurate. In this regard, it is better to determine the indicated indicators using the flow-volume curve.
Assessment of changes in speed spirographic indicators is carried out according to the degree of their deviation from the proper value. As a rule, the value of the flow indicator is taken as the lower limit of the norm, which is 60% of the proper level.
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| Spirograph MasterScreen Pneumo | Spirograph FlowScreen II |
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| Spirometer-spirograph SpiroS-100 ALTONIKA, LLC (RUSSIA) |
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Respiration rate - the number of inhalations and exhalations per unit of time. An adult makes an average of 15-17 breathing movements per minute. Training is of great importance. In trained people, respiratory movements occur more slowly and amount to 6-8 breaths per minute. Thus, in newborns, RR depends on a number of factors. When standing, the RR is greater than when sitting or lying down. During sleep, breathing is less frequent (by about 1/5).
During muscular work, breathing increases 2-3 times, reaching 40-45 cycles per minute or more in some types of sports exercises. The respiratory rate is affected by ambient temperature, emotions, and mental work.
Depth of breathing or tidal volume - the amount of air that a person inhales and exhales during quiet breathing. During each breathing movement, 300-800 ml of air in the lungs is exchanged. Tidal volume (TV) decreases with increasing respiratory rate.
Minute breathing volume- the amount of air that passes through the lungs per minute. It is determined by the product of the amount of inhaled air and the number of respiratory movements in 1 minute: MOD = DO x RR.
In an adult, the MOD is 5-6 liters. Age-related changes in external respiration parameters are presented in Table. 27.
Table 27. Indicators of external respiration (according to: Khripkova, 1990)
A newborn baby's breathing is rapid and shallow and subject to significant fluctuations. With age, there is a decrease in respiratory rate, an increase in tidal volume and pulmonary ventilation. Due to the higher respiratory rate, children have a significantly higher minute breathing volume (calculated per 1 kg of weight) than adults.
Ventilation may vary depending on the child's behavior. In the first months of life, anxiety, crying, and screaming increase ventilation by 2-3 times, mainly due to an increase in the depth of breathing.
Muscular work increases the minute volume of respiration in proportion to the magnitude of the load. The older children are, the more intense muscular work they can do and the more their ventilation increases. However, under the influence of training, the same work can be performed with a smaller increase in ventilation. At the same time, trained children are able to increase their minute volume of breathing when working to a higher level than their peers who do not engage in physical exercise (quoted from: Markosyan, 1969). With age, the effect of training is more pronounced, and in adolescents 14-15 years old, training causes the same significant changes in pulmonary ventilation as in adults.
Vital capacity of the lungs- the greatest amount of air that can be exhaled after a maximum inhalation. Vital capacity (VC) is an important functional characteristic of breathing and is composed of tidal volume, inspiratory reserve volume and expiratory reserve volume.
At rest, tidal volume is small compared to the total volume of air in the lungs. Therefore, a person can both inhale and exhale a large additional volume. Inspiratory reserve volume(PO ind) - the amount of air that a person can additionally inhale after a normal inhalation and is 1500-2000 ml. Expiratory reserve volume(PO exhalation) - the amount of air that a person can additionally exhale after a quiet exhalation; its size is 1000-1500 ml.
Even after the deepest exhalation, a certain amount of air remains in the alveoli and airways of the lungs - this residual volume(OO). However, during quiet breathing, significantly more air remains in the lungs than the residual volume. The amount of air remaining in the lungs after a quiet exhalation is called functional residual capacity(FOE). It consists of residual lung volume and expiratory reserve volume.
The largest amount of air that completely fills the lungs is called total lung capacity (TLC). It includes residual air volume and vital capacity of the lungs. The relationship between lung volumes and capacities is presented in Fig. 8 (Atl., p. 169). Vital capacity changes with age (Table 28). Since measuring the vital capacity of the lungs requires the active and conscious participation of the child himself, it is measured in children from 4-5 years of age.
By the age of 16-17 years, the vital capacity of the lungs reaches values characteristic of an adult. Vital capacity of the lungs is an important indicator of physical development.
Table 28. Average vital capacity of the lungs, ml (according to: Khripkova, 1990)
From childhood until the age of 18-19, the vital capacity of the lungs increases, from 18 to 35 years it remains at a constant level, and after 40 it decreases. This is due to a decrease in the elasticity of the lungs and the mobility of the chest.
The vital capacity of the lungs depends on a number of factors, in particular body length, weight and gender. To assess vital capacity, the proper value is calculated using special formulas:
for men:
VC should = [(height, cm∙ 0.052)] - [(age, years ∙ 0,022)] - 3,60;
for women:
VC should = [(height, cm∙ 0.041)] - [(age, years ∙ 0,018)] - 2,68;
for boys 8-10 years old:
VC should = [(height, cm∙ 0.052)] - [(age, years ∙ 0,022)] - 4,6;
for boys 13-16 years old:
VC should = [(height, cm∙ 0.052)] - [(age, years ∙ 0,022)] - 4,2
for girls 8-16 years old:
VC should = [(height, cm∙ 0.041)] - [(age, years ∙ 0,018)] - 3,7
Women have vital capacity 25% less than men; in trained people it is greater than in untrained people. It is especially high when playing sports such as swimming, running, skiing, rowing, etc. So, for example, for rowers it is 5,500 ml, for swimmers - 4,900 ml, gymnasts - 4,300 ml, football players - 4 200 ml, weightlifters - about 4,000 ml. To determine the vital capacity of the lungs, a spirometer device (spirometry method) is used. It consists of a vessel with water and another vessel with a capacity of at least 6 liters placed upside down in it, containing air. A system of tubes is connected to the bottom of this second vessel. The subject breathes through these tubes, so that the air in his lungs and in the vessel forms a single system.
Gas exchange
Content of gases in the alveoli. During the act of inhalation and exhalation, a person constantly ventilates the lungs, maintaining the gas composition in the alveoli. A person inhales atmospheric air with a high content of oxygen (20.9%) and a low content of carbon dioxide (0.03%). Exhaled air contains 16.3% oxygen and 4% carbon dioxide. When you inhale, out of 450 ml of inhaled atmospheric air, only about 300 ml enters the lungs, and approximately 150 ml remains in the airways and does not participate in gas exchange. When you exhale, which follows inhalation, this air is expelled unchanged, that is, it does not differ in composition from atmospheric air. That's why it's called air dead, or harmful, space. The air that reaches the lungs is mixed here with 3000 ml of air already in the alveoli. The gas mixture in the alveoli involved in gas exchange is called alveolar air. The incoming portion of air is small compared to the volume to which it is added, so complete renewal of all the air in the lungs is a slow and intermittent process. The exchange between atmospheric and alveolar air has little effect on the alveolar air, and its composition remains practically constant, as can be seen from Table. 29.
Table 29. Composition of inhaled, alveolar and exhaled air, in%
When comparing the composition of alveolar air with the composition of inhaled and exhaled air, it is clear that the body retains one fifth of the incoming oxygen for its needs, while the amount of CO 2 in the exhaled air is 100 times greater than the amount that enters the body during inhalation. Compared to inhaled air, it contains less oxygen, but more CO 2. Alveolar air comes into close contact with the blood, and the gas composition of arterial blood depends on its composition.
Children have a different composition of both exhaled and alveolar air: the younger the children, the lower their percentage of carbon dioxide and the higher the percentage of oxygen in exhaled and alveolar air, respectively, the lower the percentage of oxygen used (Table 30). Consequently, children have low efficiency of pulmonary ventilation. Therefore, for the same volume of oxygen consumed and carbon dioxide released, a child needs to ventilate his lungs more than adults.
Table 30. Composition of exhaled and alveolar air
(average data for: Shalkov, 1957; comp. By: Markosyan, 1969)
Since small children breathe frequently and shallowly, a large proportion of the tidal volume is the volume of “dead” space. As a result, the exhaled air consists more of atmospheric air, and has a lower percentage of carbon dioxide and a lower percentage of oxygen used from a given volume of breathing. As a result, the efficiency of ventilation in children is low. Despite the increased percentage of oxygen in the alveolar air compared to adults in children, it is not significant, since 14-15% of oxygen in the alveoli is sufficient to completely saturate the hemoglobin in the blood. More oxygen than is bound by hemoglobin cannot pass into arterial blood. The low level of carbon dioxide in the alveolar air in children indicates its lower content in the arterial blood compared to adults.
Exchange of gases in the lungs. Gas exchange in the lungs occurs as a result of the diffusion of oxygen from the alveolar air into the blood and carbon dioxide from the blood into the alveolar air. Diffusion occurs due to the difference in the partial pressure of these gases in the alveolar air and their saturation in the blood.
Partial pressure- this is the part of the total pressure that accounts for the share of a given gas in the gas mixture. The partial pressure of oxygen in the alveoli (100 mmHg) is significantly higher than the O2 tension in the venous blood entering the capillaries of the lungs (40 mmHg). The partial pressure parameters for CO 2 have the opposite value - 46 mm Hg. Art. at the beginning of the pulmonary capillaries and 40 mm Hg. Art. in the alveoli. The partial pressure and tension of oxygen and carbon dioxide in the lungs are given in table. 31.
Table 31. Partial pressure and tension of oxygen and carbon dioxide in the lungs, mmHg. Art.
These pressure gradients (differences) are the driving force for the diffusion of O 2 and CO 2, that is, gas exchange in the lungs.
The diffusion capacity of the lungs for oxygen is very high. This is due to the large number of alveoli (hundreds of millions), their large gas exchange surface (about 100 m2), as well as the small thickness (about 1 micron) of the alveolar membrane. The diffusion capacity of the lungs for oxygen in humans is about 25 ml/min per 1 mmHg. Art. For carbon dioxide, due to its high solubility in the pulmonary membrane, the diffusion capacity is 24 times higher.
Oxygen diffusion is ensured by a partial pressure difference of about 60 mmHg. Art., and carbon dioxide - only about 6 mm Hg. Art. The time for blood to flow through the capillaries of the small circle (about 0.8 s) is enough to completely equalize the partial pressure and tension of gases: oxygen dissolves in the blood, and carbon dioxide passes into the alveolar air. The transition of carbon dioxide into the alveolar air at a relatively small pressure difference is explained by the high diffusion capacity for this gas (Atl., Fig. 7, p. 168).
Thus, a constant exchange of oxygen and carbon dioxide takes place in the pulmonary capillaries. As a result of this exchange, the blood is saturated with oxygen and freed from carbon dioxide.
One of the main methods for assessing the ventilation function of the lungs used in the practice of medical labor examination is spirography, which allows you to determine statistical pulmonary volumes - vital capacity (VC), functional residual capacity (FRC), residual lung volume, total lung capacity, dynamic pulmonary volumes - tidal volume, minute volume, maximum ventilation.
The ability to fully maintain the gas composition of arterial blood does not yet guarantee the absence of pulmonary failure in patients with bronchopulmonary pathology. Blood arterialization can be maintained at a level close to normal due to compensatory overstrain of the mechanisms that provide it, which is also a sign of pulmonary failure. Such mechanisms include, first of all, the function ventilation.
The adequacy of volumetric ventilation parameters is determined by “ dynamic lung volumes", which include tidal volume And minute volume of respiration (MOV).
Tidal volume at rest in a healthy person it is about 0.5 liters. Due MAUD obtained by multiplying the required basal metabolic rate by a factor of 4.73. The values obtained in this way lie in the range of 6-9 l. However, comparison of the actual value MAUD(determined under the conditions of the basal metabolic rate or close to it) properly makes sense only for a summary assessment of changes in value, which may include both changes in ventilation itself and disturbances in oxygen consumption.
To assess the actual ventilation deviations from the norm, it is necessary to take into account Oxygen utilization factor (KIO 2)- ratio of absorbed O 2 (in ml/min) to MAUD(in l/min).
Based on oxygen utilization factor the effectiveness of ventilation can be judged. In healthy people, the CI is on average 40.
At KIO 2 below 35 ml/l ventilation is excessive in relation to the oxygen consumed ( hyperventilation), with increasing KIO 2 above 45 ml/l we are talking about hypoventilation.
Another way of expressing the gas exchange efficiency of pulmonary ventilation is by defining respiratory equivalent, i.e. the volume of ventilated air per 100 ml of oxygen consumed: determine the ratio MAUD to the amount of oxygen consumed (or carbon dioxide - DE carbon dioxide).
In a healthy person, 100 ml of oxygen consumed or carbon dioxide released is provided by a volume of ventilated air close to 3 l/min.
In patients with lung pathology and functional disorders, gas exchange efficiency is reduced, and the consumption of 100 ml of oxygen requires a greater volume of ventilation than in healthy people.
When assessing the effectiveness of ventilation, an increase breathing rate(RR) is considered as a typical sign of respiratory failure, it is advisable to take this into account during a labor examination: with degree I of respiratory failure, the respiratory rate does not exceed 24, with degree II it reaches 28, with degree III the respiratory rate is very large.
