Lung volumes table anatomy. Static lung volumes. Vital capacity of the lungs

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Common to all living cells is the process of splitting organic molecules by a successive series of enzymatic reactions, as a result of which energy is released. Almost any process in which the oxidation of organic substances leads to the release of chemical energy is called breath. If it requires oxygen, then breath is calledaerobic, and if the reactions proceed in the absence of oxygen - anaerobic breath. For all tissues of vertebrates 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 macroergic 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 breath.

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

The respiratory function in humans is realized by:

1) external, or pulmonary, respiration, which performs 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 respiration.

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.

The change in the gas composition of the blood in the lungs is provided 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 leaves the lungs during the deepest exhalation after the deepest breath, 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 at 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 a normal exhalation.

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

functional residual capacity. During quiet breathing, after expiration, the 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, balance capacity, buffer air.

functional residual capacity = expiratory reserve volume + residual volume

To assess the quality of lung function, he examines respiratory volumes (using special devices - spirometers).

Tidal volume (TO) is the amount of air that a person inhales and exhales during quiet breathing in one cycle. Normal = 400-500 ml.

Minute respiratory volume (MOD) - the volume of air passing through the lungs in 1 minute (MOD = TO x NPV). Normal = 8-9 liters per minute; about 500 liters per hour; 12000-13000 liters per day. With an increase in physical activity, the MOD increases.

Not all inhaled air is involved in the ventilation of the alveoli (gas exchange), because. some of it does not reach the acini and remains in the airways, where there is no possibility for diffusion. The volume of such airways is called "respiratory dead space". Normal in an adult = 140-150 ml, i.e. 1/3 TO.

Inspiratory reserve volume (IRV) is the amount of air that a person can inhale during the strongest maximum breath after a quiet breath, i.e. over to. Normal = 1500-3000 ml.

Expiratory reserve volume (ERV) is the amount of air that a person can additionally exhale after a normal exhalation. Normal = 700-1000 ml.

Vital capacity of the lungs (VC) - the amount of air that a person can exhale as much as possible after the deepest breath (VC=DO+ROVd+ROVd = 3500-4500 ml).

Residual lung volume (RLV) is the amount of air remaining in the lungs after maximum exhalation. Normal = 100-1500 ml.

Total lung capacity (TLC) is the maximum amount of air that can be in the lungs. TEL = VC + TOL = 4500-6000 ml.

DIFFUSION OF GAS

The composition of the inhaled air: oxygen - 21%, carbon dioxide - 0.03%.

The composition of the exhaled air: oxygen-17%, carbon dioxide - 4%.

The composition of the air contained in the alveoli: oxygen-14%, carbon dioxide -5.6% o.

As you exhale, the alveolar air mixes with the air in the airways (in the "dead space"), which causes the indicated difference in air composition.

The transition of gases through the air-blood barrier is due to the difference in concentrations on both sides of the membrane.

Partial pressure is that part of the pressure that falls on a given gas. At atmospheric pressure of 760 mm Hg, the partial pressure of oxygen is 160 mm Hg. (i.e. 21% of 760), in the alveolar air, the partial pressure of oxygen is 100 mm Hg, and carbon dioxide is 40 mm Hg.

The gas pressure is the partial pressure in the liquid. Oxygen tension in venous blood - 40 mm Hg. Due to the pressure gradient between the alveolar air and blood - 60 mm Hg. (100 mm Hg and 40 mm Hg) oxygen diffuses into the blood, where it binds to hemoglobin, turning it into oxyhemoglobin. Blood containing a large amount of oxyhemoglobin is called arterial. 100 ml of arterial blood contains 20 ml of oxygen, 100 ml of venous blood contains 13-15 ml of oxygen. Also, along the pressure gradient, carbon dioxide enters the blood (because it is contained in large quantities in tissues) and carbhemoglobin is formed. In addition, carbon dioxide reacts with water, forming carbonic acid (the reaction catalyst is the carbonic anhydrase enzyme found in erythrocytes), which decomposes into a hydrogen proton and a bicarbonate ion. CO 2 tension in venous blood - 46 mm Hg; in the alveolar air - 40 mm Hg. (pressure gradient = 6 mmHg). Diffusion of CO 2 occurs from the blood into the external environment.

Lung ventilation is a continuous regulated process of updating the gas composition of the air contained in the lungs. Ventilation of the lungs is provided by the introduction of atmospheric air rich in oxygen into them, and the removal of gas containing excess carbon dioxide during exhalation.

Pulmonary ventilation is characterized by minute respiratory volume. At rest, an adult inhales and exhales 500 ml of air at a frequency of 16-20 times per minute (minute 8-10 liters), a newborn breathes more often - 60 times, a child of 5 years old - 25 times per minute. The volume of the respiratory tract (where gas exchange does not occur) is 140 ml, the so-called air of the harmful space; thus, 360 ml enters the alveoli. Rare and deep breathing reduces the amount of harmful space, and it is much more effective.

Static volumes include values ​​that are measured after the completion of a respiratory maneuver without limiting the speed (time) of its implementation.

The static indicators include four primary lung volumes: - tidal volume (TO - VT);

Inspiratory reserve volume (IRV);

Expiratory reserve volume (ERV - ERV);

Residual volume (OO - RV).

As well as containers:

Vital capacity of the lungs (VC - VC);

Inspiratory capacity (Evd - IC);

Functional residual capacity (FRC - FRC);

Total lung capacity (TLC).

Dynamic quantities characterize the volumetric velocity of the air flow. They are determined taking into account the time spent on the implementation of the respiratory maneuver. Dynamic indicators include:

Forced expiratory volume in the first second (FEV 1 - FEV 1);

Forced vital capacity (FZhEL - FVC);

Peak volumetric (PEV) expiratory flow rate (PEV), etc.

The volume and capacity of the lungs of a healthy person is determined by a number of factors:

1) height, body weight, age, race, constitutional features of a person;

2) elastic properties of lung tissue and airways;

3) contractile characteristics of the inspiratory and expiratory muscles.

Spirometry, spirography, pneumotachometry and body plethysmography are used to determine lung volumes and capacities.

For comparability of the results of measurements of lung volumes and capacities, the obtained data should be correlated with standard conditions: body temperature 37 ° C, atmospheric pressure 101 kPa (760 mm Hg), relative humidity 100%.

Tidal volume

Tidal volume (TO) 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).

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

expiratory reserve volume

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

Inspiratory reserve volume

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

Vital capacity of the lungs

Vital capacity (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 of air (the so-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.

The vital capacity of the lungs is an indicator of the mobility of the lungs and chest. Despite the name, it does not reflect the parameters of respiration in real (“life”) conditions, since even with the highest needs that the body has for the respiratory system, the depth of respiration never reaches the maximum possible value.

From a practical point of view, it is not advisable to establish a “single” norm 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 an average of 25% less than men.

Growth dependence can be calculated using the following equation:

VC=2.5*height (m)

VC depends on the position of the body: in a vertical position, it is somewhat greater than in a horizontal position.

This is explained by the fact that in an upright position, less blood is contained in the lungs. In trained people (especially swimmers, 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 1000 - 1500 ml.

Total lung capacity

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

The study of respiratory volumes is necessary to assess the compensation of 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 the start of swimming or running, the vital capacity of the lungs in young athletes can increase by 500 cc. and more. Its decrease 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 cork and disinfect its mouthpiece with alcohol. After a deep breath, take a deep breath through the mouthpiece taken into your mouth. In this case, the air should not pass by 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. Reducing it by more than 300 cc may indicate overwork.

It is very important to learn full deep breathing, to avoid delaying it. If at rest the respiratory rate is usually 16-18 per minute, then during physical exertion, when the body needs more oxygen, this frequency can reach 40 or more. If you experience frequent shallow breathing, shortness of breath, you need to stop exercising, note this in the self-control diary and consult a doctor.

LUNG, PLEURA.

LECTURE №30.

1. The structure of the lungs and pleura.

2. Pneumothorax and its types.

3. Respiratory cycle. Mechanisms of inhalation and exhalation.

4. Lung volumes. Pulmonary ventilation.

PURPOSE: To know the topography, the structure of the lungs, the pleura, the respiratory cycle, the mechanisms of inhalation and exhalation, lung volumes, minute respiratory volume.

Present the mechanism of pneumothorax and the main types of pneumothorax.

To be able to show the borders of the lungs on the human skeleton.

1. Lungs (pulmones; Greek pneumones) are paired respiratory organs, which are hollow sacs of a cellular structure, subdivided into thousands of separate sacs (alveoli) with moist walls, equipped with a dense network of blood capillaries. The branch of medicine that studies the structure, functions and diseases of the lungs is called pulmonology.

The lungs are located in a hermetically sealed thoracic cavity and

separated from each other by the mediastinum, which includes the heart, large vessels (aorta, superior vena cava), esophagus and other organs. In shape, the lung resembles an irregular cone with a base facing the diaphragm and an apex protruding 2-3 cm above the collarbone in the neck. On each lung, 3 surfaces are distinguished: diaphragmatic, costal and medial, and two edges: anterior and inferior. The costal and diaphragmatic surfaces are separated from each other by a sharp lower edge and are adjacent to the ribs, intercostal muscles and the dome of the diaphragm, respectively. The medial surface, facing the mediastinum, is separated from the costal surface by the anterior edge of the lung. On the medial (mediastinal) surface of both lungs are the gates of the lung, through which the main bronchi, vessels and nerves that make up the root of the lung pass.

Each lung is divided into lobes by means of furrows. In the right lung

there are 3 lobes: upper, middle and lower, in the left - 2 lobes: upper and lower. The lobes are divided into segments (10 in each lung). Each lung lobule contains 16-18 acini. The acinus starts from the terminal bronchiole, which is dichotomously divided into respiratory bronchioles of 1-2-3 orders and passes into the alveolar passages and alveolar sacs with the alveoli of the lungs located on their walls. The number of pulmonary acini in one lung reaches 150,000. Each acinus includes a large number of alveoli.

Alveoli are protrusions in the form of bubbles with a diameter of up to 0.25 mm,

the inner surface of which is lined with a single-layer squamous epithelium, located on a network of elastic fibers and braided from the outside with blood capillaries. From the inside, the alveoli are covered with a thin film of phospholipid - a surfactant that performs many important functions:

1) lowers the surface tension of the alveoli; 2) increases the extensibility of the lungs; 3) ensures the stability of the pulmonary alveoli, preventing them from spa-

denia, adhesion and the appearance of atelectasis; 4) prevents the extravasation (exit) of fluid to the surface of the alveoli from the plasma of the capillaries of the lungs.

The number of alveoli in both lungs in an adult is from 600 to 700 million, and the total respiratory surface of all alveoli is 100 sq.m.

In addition to the respiratory function, the lungs carry out the regulation of water metabolism, participate in the processes of thermoregulation, and are a blood depot (0.5-1.2 l).

In clinical practice, it is necessary to determine the boundaries of the lungs: anterior, inferior and posterior. The tops of the lungs protrude 2-3 cm above the clavicle. The anterior border (projection of the anterior edge) descends from the tops of both lungs along the sternum, runs almost parallel at a distance of 1-1.5 cm to the level of the IV rib cartilage. Here, the border of the left lung deviates to the left by 4-5 cm, forming a cardiac notch. At the level of the cartilage of the VI ribs, the anterior borders of the lungs pass into the lower ones. The lower border of the lungs corresponds to the VI rib along the midclavicular line, the VIII rib along the midaxillary line, the X rib along the scapular line, and the XI rib along the paravertebral line. The lower border of the left lung is located 1-2 cm below the given border of the right lung. With maximum inspiration, the lower edge of the lung descends by 5-7 cm. The posterior border of the lungs passes along the paravertebral line (along the heads of the ribs).

Outside, each lung is covered with a serous membrane - the pleura, consisting of two sheets: parietal (parietal) and pulmonary (visceral). Between the sheets of the pleura there is a capillary gap filled with serous fluid - the pleural cavity. This fluid reduces friction between the layers of the pleura during respiratory movements. In places where one part of the parietal pleura passes into another, spare spaces are formed - the pleural sinuses, which are filled with the lungs at the moment of maximum inspiration (the costophrenic sinus, located in the lower part of the pleural cavity, is especially large). The right and left pleural cavities do not communicate with each other. Normally, there is no air in the pleural cavity, and the pressure in it is always negative, i.e. below atmospheric. During a quiet breath, it is 6-8 cm of water. Art. below atmospheric, during a quiet exhalation - by 4-5 cm of water. Art. Due to the negative pressure in the pleural cavities, the lungs are

dyatsya in a straightened state, taking the configuration of the wall of the chest cavity.

The value of negative intrathoracic pressure:

1) promotes stretching of the pulmonary alveoli and an increase in the respiratory surface of the lungs, especially during inspiration;

2) provides venous return of blood to the heart and improves blood circulation in the pulmonary circle, especially in the inhalation phase;

3) promotes lymph circulation;

4) helps to move the food bolus through the esophagus.

Inflammation of the lungs is called pneumonia, inflammation of the pleura is called pleurisy. The accumulation of fluid in the pleural cavity is called hydrothorax, blood - hemothorax, purulent exudate - pyothorax.

2. Pneumothorax is an accumulation of air in the pleural cavity, the following types of pneumothorax are distinguished: 1) traumatic; 2) spontaneous (spontaneous); 3) artificial.

Traumatic pneumothorax occurs when a penetrating wound of the chest. Depending on the connection (message) of the pleural cavity with atmospheric air, it can be closed, open and valvular. With a closed pneumothorax, air enters the pleural cavity once at the time of injury. There is no communication between the pleural cavity and the atmosphere. It is not dangerous, since the air is quickly absorbed or removed during puncture. With an open pneumothorax, air freely enters the pleural cavity and leaves it, the lung collapses, turns off from breathing. Very dangerous due to the development of severe shock. With valvular (tense) pneumothorax, air enters the pleural cavity during inspiration and does not exit during expiration. An urgent puncture of the pleural cavity with a thick needle is required in the second or third intercostal space along the midclavicular line. In addition, an occlusive (Latin occlusus - locked) bandage should be applied to the wounded in the chest.

Spontaneous (spontaneous) pneumothorax is formed when a diseased lung spontaneously ruptures (cavernous tuberculosis,

abscess, gangrene, cancer), when air enters the pleural cavity through the damaged wall of the bronchus.

An artificial pneumothorax is created intentionally with medical

purpose (for pulmonary tuberculosis), for diagnosis (for tumors and foreign bodies of the chest cavity) and for preparing the patient for light and mediastinal surgery.

3. The respiratory cycle consists of inhalation (0.9 - 4.7 s), exhalation (1.2 - 6 s) and pause (may be absent). The respiratory rate, determined by the number of chest excursions per minute, is normal in adults 12-18 per minute, in newborns - 60, in five-year-old children - 25 excursions per minute. At any age, the respiratory rate is 4-5 times less than the heart rate.

Inhalation (inspiration) occurs due to an increase in the volume of the chest in three directions: vertical, sagittal, frontal, mainly due to contraction of the external intercostal muscles and flattening of the dome of the diaphragm. When inhaling, the lungs passively follow the expanding chest. The respiratory surface of the lungs increases, while the pressure in them decreases and becomes 2 mm Hg. below atmospheric. This promotes the flow of air through the respiratory tract into the lungs. The rapid equalization of pressure in the lungs is prevented by the glottis, since in this place the airways are narrowed. Only at the height of inhalation is the complete filling of the expanded alveoli of the lungs with air.

Exhalation (expiration) is carried out as a result of relaxation of the external intercostal muscles and raising the dome of the diaphragm. In this case, the chest returns to its original position and the respiratory surface of the lungs decreases. Stretched lungs due to their elasticity decrease in volume. The air pressure in the lungs becomes 3-4 mm Hg. above atmospheric, which facilitates the release of air from them into the environment. The slow exit of air from the lungs contributes to the narrowing of the glottis.

4. In everyday clinical practice, the determination of four lung volumes and four lung capacities is used. For this purpose, special devices are used: spirometers and spirographs.

Lung volumes.

1) Tidal volume - the amount of air that a person inhales and exhales at rest: 300-700 ml (average 500 ml).

2) Inspiratory reserve volume - the amount of air that a person can additionally inhale after a normal quiet breath: 1500-2000 ml (usually 1500 ml).

3) Expiratory reserve volume - the amount of air that a person can additionally exhale after a quiet exhalation: 1500-2000 ml (usually 1500 ml).

4) Residual volume - the amount of air remaining in the lungs after maximum exhalation: 1000-1500 ml (average 1200 ml).

Lung capacities.

1) Vital capacity of the lungs - the largest amount of air that

can be exhaled after maximum inhalation. Equal to the sum of the respiratory

volume, inspiratory and expiratory reserve volume (from 3500 to 4700 ml).

2) Total lung capacity - the amount of air contained in the lungs at the height of maximum inspiration. It is equal to the sum of the vital capacity of the lungs and the residual volume (4700-6000 ml).

3) Inspiratory reserve (capacity) - the maximum amount of air that can be inhaled after a quiet exhalation. Equal to the sum of tidal volume and inspiratory reserve volume (2000 ml).

4) Functional residual capacity - the amount of air remaining in the lungs after a quiet exhalation. It is equal to the sum of the expiratory reserve volume and the residual volume (2700-2900 ml). The physiological significance of the functional residual capacity is that it helps to equalize the fluctuations in the content of oxygen and carbon dioxide in the alveolar air due to the different concentrations of these gases in the inhaled and exhaled air.

Pulmonary ventilation is the amount of air passing through

lungs per unit time. Minute volume of respiration (MOD) is usually measured, equal to the product of tidal volume and respiratory rate. At rest, the minute volume of breathing is 6-8 l / min, with moderate muscular work it is 80 l / min, and with heavy muscular work it reaches 120-150 l / min.

There are four primary lung volumes and four lung capacities. Each container includes at least two lung volumes (Fig. 4).

Rice. 4. The constituent elements of the lung volume (Pappenheimer, 1950).

The volume of gas inhaled or exhaled in each breath is called the tidal volume (VT). With calm breathing, it is about 500 ml in adults. Approximately 150 ml of this volume fills the conducting airways - from the nasal cavity and mouth to the respiratory bronchioles - and does not take part in gas exchange; this is the anatomical dead space (VD). 350 ml remain for alveolar ventilation (VA). They mix with the volume of air remaining in the lungs after a quiet expiration (functional residual capacity - FRC), which varies from 1800 ml in small women to 3500 ml in large men. At a respiratory rate of 12 per minute, VA would be about 12X350 ml, or 4.2 L/min. Calculating alveolar ventilation in this way is an oversimplification that assumes that the inhaled gas moves in a straight line, when in fact it is a wedge-shaped movement. A forward airflow front would mean that with Vm reduced to Vd, alveolar ventilation would be 0. Because this front is wedge-shaped, some alveolar ventilation, albeit very small, may occur even if VT is less than VD. Thus, the above ventilation calculation method is inaccurate when VT is reduced to a large extent.

When the alveolar pressure (PA) becomes equal to atmospheric pressure, exhalation stops and the air flow stops. At this point there is a balance between the elastic recoil of the lung and the tendency of the chest to expand. With the contraction of the muscles involved in exhalation, mainly the abdominal muscles, it is possible to exhale an additional volume of air. This is the expiratory reserve volume (POexp.), which varies according to the size of the tidal volume. The amount of gas remaining in the lungs after maximum exhalation is the residual volume (00), which usually approaches 1200 ml. The residual volume is less than 30% of the total lung capacity (TLC) - the amount of gas that is contained in the lungs at the end of a maximum breath. Vital capacity (VC) is the maximum volume of air that can be exhaled after a maximum inhalation. In young healthy individuals, the vital capacity is about 80% of the total lung capacity. When maximum exhalation is made in the study of vital capacity, the air current is continued by the efforts of the respiratory muscles until the pressure in the lung tissue exceeds that in the lumen of the small airways, which then collapse, holding a residual volume that can never be exhaled in life. Inspiratory capacity (Eu) is the maximum volume of air that can be inhaled after a quiet exhalation. It makes up about 75% of VC. Inspiratory reserve volume (RIV) is the maximum volume of air that can be inhaled after a normal inspiration.

Methods for measuring lung volumes. Vital capacity and its divisions (RV, RV and VT) are measured directly by conventional spirometry. Residual volume or functional residual capacity can be measured by the degree of change in the concentration of a known volume of an inert gas (usually helium) when a given volume is breathed into the spirometer. Volume constancy is maintained by adding O 2 at the same rate as exhaled CO 2 is removed by the absorber. The REL can also be measured by this method, but it is usually calculated by summing the FRC and Evd. or OO and YEL. By making successive measurements after maximum exhalation, at the end of normal expiration and with full inspiration, the values ​​of OO, FFU and TEL are obtained, respectively. The following formulas apply:

where V is the volume of the spirometer, a is the initial helium concentration in percent, b is the helium concentration in percent at the end of equilibration, and the asterisk indicates the calculated values ​​(00, FFU or TEL).

These quantities can also be determined by the open system method using nitrogen clearance. Nitrogen is leached out of the lungs when oxygen is breathed in, and the volume of exhaled nitrogen is calculated by analyzing the nitrogen content of the exhaled air using a nitrometer.

The formula is:

where V is the volume of the spirometer, a is the initial concentration of nitrogen in the lungs, b is the final concentration of nitrogen in the system spirometer - lungs, the calculated value is indicated by an asterisk.

You can see that:
Evd. = OEL - FOE;
OO \u003d FOE - ROvyd .;
OEL \u003d OO + VC \u003d FOE + Evd.

Clinical significance of lung volume and capacity options. Statistical lung volumes are essentially anatomical quantities and cannot be used to evaluate function, while changes in lung volumes may be associated with pathology affecting function.

With a temperature change of 0.01°, the difference in tidal volumes is 0.5% and therefore lung volumes must be adjusted to body temperature and water vapor saturation pressure (BTPS).

The surgeon John Hutchinson in 1844 became convinced that the vital capacity was greater in summer than in winter, and therefore brought the volumes to an average room temperature, which at that time was 15 °.