Lung volume. Open Library - open library of educational information What does lung volume affect?

In men, abdominal breathing predominates. When the chest enlarges due to contractions of the diaphragm. In females, it’s the other way around – the chest type of breathing, as they experience an increase in the transverse size of the chest. That’s why there is a saying that women breathe with their chests, and men breathe with their stomachs.

During quiet inhalation and exhalation, adults breathe 16 to 20 times per minute. The respiratory rate also depends on body weight. Big, heavy women breathe slowly, while thin, short people breathe faster. Because they are more active.

When a person breathes calmly, he uses approximately 500 ml of air mass to inhale and exhale. This amount of air is called breathing volume. If you take a deep breath, you can increase this amount by 1500 ml. This is called reserve air volume. And, conversely, during a quiet exhalation, a person is able to exhale up to an additional 1500 ml. This is called expiratory reserve volume.

These volumes in their combination constitute the volumetric (vital) capacity of the lungs.

What is lung capacity

This volume is also called pulmonary capacity. This is the amount of air flow that passes through the respiratory organs. At different phases of the breathing cycle. Lung size is measured directly. In simple terms, this is when a person inhales and exhales air, its quantity is considered the volume of the lung, as in some vessel - how much air mass can enter the respiratory organ.

The average capacity of a man's lung is a maximum of 3 to 6 liters. The usual rate is from 3 to 4 liters. But only a small part of this air is used for normal breathing.

Normal breathing volume is the portion of air that passes through the respiratory organs during inhalation and exhalation.

Factors that affect lung volume

There are various factors that influence lung size: height, lifestyle, gender, place of residence. There is a scientific table of such factors:

• Large lung sizes are found in people in the following categories - tall, with a healthy lifestyle (non-smokers), asthenics, males, as well as those who live above sea level.
• Low capacity of the respiratory organs is observed in short people, smokers, hypersthenics, women, elderly people, and those who live at sea level.

People who spend most of their lives at sea level have low lung capacity and vice versa. This is a result of the pressure being less in the atmosphere at high levels. As a result, the penetration of oxygen into the body is difficult. Adapting to this situation, air conductivity to tissues increases.

During pregnancy, the size of the lungs changes. It decreases to 1.3 liters. This occurs because the uterus puts pressure on the chest septum (diaphragm). This also leads to a decrease in the total capacity of the organ by up to 5%. And the reserve volume of exhaled air decreases. The average capacity of a woman's lung is 3.5 liters.

An increased figure is observed in active people - athletes, dancers, etc. (up to 6 liters). Since their body is trained, the entire volume of the organ is used for exhalations and inhalations. And in the weak, who do not engage in sports, only one third of the volume is involved in the breathing process.

How are lung volumes measured?

To measure the total volume of an organ, the following indicators are usually taken.

• total capacity;
• residual capacity;
• functional residual capacity;
• vital capacity.

The combination of these indicators is used in the analysis of the organ. This makes it possible to assess the ventilation capacity of the lungs, diagnose ventilation disorders, and evaluate the therapeutic effect in diseases.

The simplest and most commonly used measurement method is gas dilution. It is carried out by doctors using special equipment.

It is difficult to calculate the capacity of the lung with reliable accuracy, since this organ is a kind of muscle. Capable of expanding if necessary. But the average size of an adult’s lung rests precisely on these numbers.

Vital capacity of the lungs- this is an important parameter that reflects the state of the human respiratory system.

The larger the lung volume of an adult, the faster and better the body tissues are saturated with oxygen.

Special exercises aimed at proper breathing and a healthy lifestyle will help increase lung capacity.

How much oxygen can the lungs hold?

Knowing the standard lung volume indicators is very important, since a constant lack of oxygen can lead to various complications of the respiratory system and serious consequences.

So, when undergoing a clinical and dispensary examination in case of suspected diseases of the cardiovascular system, the doctor will prescribe a measurement of the vital capacity of the lungs.

Lung volume is an important indicator that indicates how much the human body is saturated with oxygen. The tidal volume of the lungs is the amount of air that enters the body when you inhale and leaves it when you exhale.

The average amount of air inhaled and exhaled for an adult is about 1 liter in ten seconds is approximately 16-20 breaths per minute.

Pulmonologists identify several factors that have a positive effect on lung volume in the direction of increasing:

• Tall.
• No smoking habit.
• Living in regions that are located high above sea level (prevalence of high pressure, “rarefied” air).

Short stature and smoking slightly reduce lung capacity.

There is vital capacity (vital capacity), which indicates the volume of air that a person maximally exhales after the largest inhalation.

How many ml is the stomach of a healthy person?

This figure is measured in liters and depends on several factors, including age, height and weight.

The average norm is as follows: in healthy normal men the size is from 3000 to 4000 ml, and in women - from 2500 to 3000 ml.

The size of vital capacity can be significantly increased in athletes, in particular in swimmers (for professional swimmers vital capacity is 6200 ml), in people who regularly perform heavy physical activity, as well as those who sing and play wind instruments.

How to measure vital capacity

The vital capacity of the lungs is a very important medical indicator, which is determined by a device for measuring lung volume. This device is called a spirometer. As a rule, it is used to find out vital capacity in medical institutions: hospitals, clinics, dispensaries, as well as sports centers.

Checking vital capacity using spirometry is quite simple and effective, which is why the device is widely used for diagnosing lung and heart diseases at the initial stage. You can measure vital vitality at home with an inflatable round ball.

The amount of vital capacity in women, men and children is calculated using special empirical formulas, which depend on the person’s age, gender and height. There are special tables with already calculated values ​​using the formula of the physicist Ludwig.

So, the average vital capacity in an adult should be 3500 ml. If the deviation from the table data exceeds more than 15%, this means that the respiratory system is in good condition.

When vital capacity is significantly lower, it is necessary to seek advice and subsequent examination from a specialist.

VC in children

Before checking the vital capacity of a child’s lungs, it is worth considering that their size is more labile than that of adults. In young children, it depends on a number of factors, which include: the sex of the child, the circumference and mobility of the chest, height, and the condition of the lungs at the time of testing (presence of diseases).

The volume of a child’s lungs increases as a result of muscle training (exercises, active games in the air) carried out by parents.

Reasons for deviation of vital capacity from standard indicators

In the case when vital capacity decreases so much that it begins to negatively affect the functioning of the lungs, various pathologies can be observed.

• Diffuse bronchitis.
• Fibrosis of any kind.
• Emphysema.
• Bronchospasm or bronchial asthma.
• Atelectasis.
• Various chest deformities.

The main causes of VC impairment

Clinicians consider three main deviations to be the main violations of stable indicators of vital capacity:

1. Loss of functioning lung parenchyma.
2. Significant reduction in the capacity of the pleural cavity.
3. Rigidity of the lung tissue.

Refusal timely treatment can affect the formation of a restrictive or limited type of respiratory failure.

The most common diseases that affect lung function are:

• Pneumothorax.
• Ascites.
• Pleurisy.
• Hydrothorax.
• Pronounced kyphoscoliosis.
• Obesity.

At the same time, the range of pulmonary diseases that affect the normal functioning of the alveoli in the process of air processing and the formation of the respiratory system is quite large.

This includes such severe forms of pathologies as:

• Pneumosclerosis.
• Sarcoidosis.
• Diffuse connective tissue diseases.
• Hamman-Rich syndrome.
• Beryllium.

Regardless of the disease that provoked a disruption in the functioning of the body, which is ensured by the vital capacity of a person, patients must undergo diagnostics for preventive purposes at certain intervals.

How to increase vital capacity

You can increase the vital capacity of the lungs by performing breathing exercises, playing sports and performing simple exercises specially developed by sports instructors.

Aerobic sports are ideal for this purpose: swimming, rowing, race walking, skating, skiing, cycling and mountaineering.

You can increase the volume of inhaled air without exhausting and long-term physical exercise. To do this, you need to monitor proper breathing in everyday life.

1. Take full and even exhalations.
2. Breathe with your diaphragm. Chest breathing significantly limits the amount of oxygen that enters the lungs.
3. Arrange “minutes of rest”. During this short period, you need to take a comfortable position and relax. Inhale/exhale slowly and deeply with short delays for a count, at a comfortable rhythm.
4. When washing your face, hold your breath for a few seconds., since it is when washing that the “diving” reflex occurs.
5. Avoid visiting heavily smoky places. Passive smoking also negatively affects the entire respiratory system, just like active smoking.
6. Breathing exercises allow you to significantly improve blood circulation, which also contributes to better gas exchange in the lungs.
7. Ventilate the room regularly, carry out wet cleaning of premises, since the presence of dust has a bad effect on the functioning of the lungs.
8. Yoga classes- a fairly effective method that promotes a rapid increase in breathing volume, which includes a whole section devoted to exercises and breathing aimed at development - pranayama.

Warning: If dizziness occurs during physical activity and breathing exercises, you should immediately stop them and return to a state of rest to restore normal breathing rhythm.

Prevention of lung diseases

One of the significant factors that contributes to good performance and maintenance of human health is sufficient vital capacity of the lungs.

A properly developed chest provides a person with normal breathing, which is why morning exercises and other active sports with moderate loads are so important for its development and significantly increase lung capacity.

Fresh air has a positive effect on the human body, and vital capacity directly depends on its purity. The air in closed, stuffy rooms is saturated with carbon dioxide and water vapor, which has a negative effect on the respiratory system.

This can be said about inhaling dust, contaminated particles and smoking.

Health measures aimed at purifying the air include: landscaping residential areas, watering and asphalt streets, ventilation absorbing devices in apartments and houses, installing smoke extractors on the pipes of enterprises.

Ventilation is a continuous, controlled process of updating the gas composition of the air contained in the lungs. Ventilation of the lungs is ensured 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 the minute volume of breathing. At rest, an adult inhales and exhales 500 ml of air at a frequency of 16-20 times per minute (minute 8-10 l), a newborn breathes more often - 60 times, a 5-year-old child - 25 times per minute. The volume of the respiratory tract (where gas exchange does not occur) is 140 ml, the so-called harmful air; thus, 360 ml enters the alveoli. Infrequent and deep breathing reduces the volume of harmful space, and it is much more effective.

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

Static indicators include four primary pulmonary volumes: - tidal volume (VT - VT);

Inspiratory reserve volume (IRV);

Expiratory reserve volume (ERV);

Residual volume (RO - RV).

And also 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 speed of air flow. They are determined taking into account the time spent performing the breathing maneuver. Dynamic indicators include:

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

Forced vital capacity (FVC);

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

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

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

2) elastic properties of lung tissue and respiratory tract;

3) contractile characteristics of inspiratory and expiratory muscles.

To determine pulmonary volumes and capacities, the methods of spirometry, spirography, pneumotachometry and body plethysmography are used.

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

Tidal volume

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.

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

The entire complex process can be divided into three main stages: external respiration; and internal (tissue) respiration.

External breathing- gas exchange between the body and the surrounding atmospheric air. External respiration involves the exchange of gases between atmospheric and alveolar air, as well as pulmonary capillaries and alveolar air.

This breathing occurs as a result of periodic changes in the volume of the chest cavity. An increase in its volume provides inhalation (inspiration), a decrease provides exhalation (expiration). The phases of inhalation and subsequent exhalation are . During inhalation, atmospheric air enters the lungs through the airways, and when exhaling, some of the air leaves them.

Conditions necessary for external respiration:

• chest tightness;
• free communication of the lungs with the surrounding external environment;
• elasticity of lung tissue.

An adult takes 15-20 breaths per minute. The breathing of physically trained people is rarer (up to 8-12 breaths per minute) and deeper.

The most common methods for studying external respiration

Methods for assessing respiratory function of the lungs:

• Pneumography
• Spirometry
• Spirography
• Pneumotachometry
• Radiography
• X-ray computed tomography
• Ultrasound examination
• Magnetic resonance imaging
• Bronchography
• Bronchoscopy
• Radionuclide methods
• Gas dilution method

Spirometry- a method of measuring the volume of exhaled air using a spirometer device. Various types of spirometers with a turbimetric sensor are used, as well as water ones, in which exhaled air is collected under a spirometer bell placed in water. The volume of exhaled air is determined by the rise of the bell. Recently, sensors sensitive to changes in volumetric air flow velocity connected to a computer system have been widely used. In particular, a computer system such as “Spirometer MAS-1” of Belarusian production, etc., operates on this principle. Such systems make it possible to carry out not only spirometry, but also spirography, as well as pneumotachography).

Spirography - a method of continuously recording the volumes of inhaled and exhaled air. The resulting graphical curve is called spirophamma. Using a spirogram, you can determine the vital capacity of the lungs and tidal volumes, respiratory rate and voluntary maximum ventilation of the lungs.

Pneumotachography - method of continuous recording of the volumetric flow rate of inhaled and exhaled air.

There are many other methods for studying the respiratory system. Among them are plethysmography of the chest, listening to sounds produced when air passes through the respiratory tract and lungs, fluoroscopy and radiography, determination of the oxygen and carbon dioxide content in the exhaled air flow, etc. Some of these methods are discussed below.

Volume indicators of external respiration

The relationship between lung volumes and capacities is presented in Fig. 1.

When studying external respiration, the following indicators and their abbreviations are used.

Total lung capacity (TLC)- the volume of air in the lungs after the deepest possible inspiration (4-9 l).

Rice. 1. Average values ​​of lung volumes and capacities

Vital capacity of the lungs

Vital capacity of the lungs (VC)- the volume of air that a person can exhale with the deepest, slowest exhalation made after a maximum inhalation.

The vital capacity of the human lungs is 3-6 liters. Recently, due to the introduction of pneumotachographic technology, the so-called forced vital capacity(FVC). When determining FVC, the subject must, after inhaling as deeply as possible, make the deepest possible forced exhalation. In this case, exhalation should be made with an effort aimed at achieving the maximum volumetric speed of the exhaled air flow throughout the entire exhalation. Computer analysis of such forced exhalation makes it possible to calculate dozens of indicators of external respiration.

The individual normal value of vital capacity is called proper lung capacity(JEL). It is calculated in liters using formulas and tables based on height, body weight, age and gender. For women aged 18-25, the calculation can be made using the formula

JEL = 3.8*P + 0.029*B - 3.190; for men of the same age

Residual volume

JEL = 5.8*P + 0.085*B - 6.908, where P is height; B—age (years).

The value of the measured VC is considered reduced if this decrease is more than 20% of the VC level.

If the name “capacity” is used for the indicator of external respiration, this means that the composition of such a capacity includes smaller units called volumes. For example, TLC consists of four volumes, vital capacity - of three volumes.

Tidal volume (TO)- this is the volume of air entering and leaving the lungs in one respiratory cycle. This indicator is also called the depth of breathing. At rest in an adult, the DO is 300-800 ml (15-20% of the VC value); one month old baby - 30 ml; one year old - 70 ml; ten years old - 230 ml. If the depth of breathing is greater than normal, then such breathing is called hyperpnea- excessive, deep breathing, but if DO is less than normal, then breathing is called oligopnea- insufficient, shallow breathing. At normal depth and frequency of breathing it is called eupnea- normal, sufficient breathing. The normal resting respiratory rate in adults is 8–20 breaths per minute; a month-old baby - about 50; one year old - 35; ten years old - 20 cycles per minute.

Inspiratory reserve volume (IR ind)- the volume of air that a person can inhale with the deepest possible breath taken after a calm breath. The normal PO value is 50-60% of the VC value (2-3 l).

Expiratory reserve volume (ER ext)- the volume of air that a person can exhale with the deepest exhalation made after a calm exhalation. Normally, the RO value is 20-35% of vital capacity (1-1.5 l).

Residual lung volume (RLV)- air remaining in the respiratory tract and lungs after maximum deep exhalation. Its value is 1-1.5 l (20-30% of TEL). In old age, the value of TRL increases due to a decrease in the elastic traction of the lungs, bronchial patency, a decrease in the strength of the respiratory muscles and the mobility of the chest. At the age of 60 years, it is already about 45% of the TEL.

Functional residual capacity (FRC)- air remaining in the lungs after a quiet exhalation. This capacity consists of residual lung volume (RLV) and expiratory reserve volume (ER ext).

Not all atmospheric air entering the respiratory system during inhalation takes part in gas exchange, but only that which reaches the alveoli, which have a sufficient level of blood flow in the capillaries surrounding them. In this regard, there is something called dead space.

Anatomical dead space (AMP)- this is the volume of air located in the respiratory tract to the level of the respiratory bronchioles (these bronchioles already have alveoli and gas exchange is possible). The size of the AMP is 140-260 ml and depends on the characteristics of the human constitution (when solving problems in which it is necessary to take into account the AMP, but its value is not indicated, the volume of the AMP is taken equal to 150 ml).

Physiological dead space (PDS)- the volume of air entering the respiratory tract and lungs and not participating in gas exchange. The FMP is larger than the anatomical dead space, since it includes it as an integral part. In addition to the air in the respiratory tract, the FMF includes air that enters the pulmonary alveoli, but does not exchange gases with the blood due to the absence or reduction of blood flow in these alveoli (this air is sometimes called alveolar dead space). Normally, the value of functional dead space is 20-35% of the tidal volume. An increase in this value above 35% may indicate the presence of certain diseases.

Table 1. Indicators of pulmonary ventilation

In medical practice, it is important to take into account the dead space factor when designing breathing devices (high-altitude flights, scuba diving, gas masks), and carrying out a number of diagnostic and resuscitation measures. When breathing through tubes, masks, hoses, additional dead space is connected to the human respiratory system and, despite the increase in the depth of breathing, ventilation of the alveoli with atmospheric air may become insufficient.

Minute breathing volume

Minute respiration volume (MRV)— volume of air ventilated through the lungs and respiratory tract in 1 minute. To determine the MOR, it is enough to know the depth, or tidal volume (TV), and respiratory frequency (RR):

MOD = TO * BH.

In mowing, MOD is 4-6 l/min. This indicator is often also called pulmonary ventilation (distinguished from alveolar ventilation).

Alveolar ventilation

Alveolar ventilation (AVL)- the volume of atmospheric air passing through the pulmonary alveoli in 1 minute. To calculate alveolar ventilation, you need to know the value of the AMP. If it is not determined experimentally, then for calculation the volume of AMP is taken equal to 150 ml. To calculate alveolar ventilation, you can use the formula

AVL = (DO - AMP). BH.

For example, if a person’s breathing depth is 650 ml and the respiratory rate is 12, then AVL is 6000 ml (650-150). 12.

AB = (DO - WMD) * BH = DO alv * BH

• AB - alveolar ventilation;
• DO alve - tidal volume of alveolar ventilation;
• RR - respiratory rate

Maximum ventilation (MVV)- the maximum volume of air that can be ventilated through a person’s lungs in 1 minute. MVL can be determined by voluntary hyperventilation at rest (breathing as deeply as possible and often at a slant is permissible for no more than 15 seconds). With the help of special equipment, MVL can be determined while a person is performing intense physical work. Depending on the constitution and age of a person, the MVL norm is within the range of 40-170 l/min. In athletes, MVL can reach 200 l/min.

Flow indicators of external respiration

In addition to lung volumes and capacities, so-called flow indicators of external respiration. The simplest method for determining one of them, peak expiratory flow rate, is peak flowmetry. Peak flow meters are simple and quite affordable devices for use at home.

Peak expiratory flow rate(POS) - the maximum volumetric flow rate of exhaled air achieved during forced exhalation.

Using a pneumotachometer device, you can determine not only the peak volumetric flow rate of exhalation, but also inhalation.

In a medical hospital, pneumotachograph devices with computer processing of the received information are becoming increasingly common. Devices of this type make it possible, based on continuous recording of the volumetric velocity of the air flow created during exhalation of the forced vital capacity of the lungs, to calculate dozens of indicators of external respiration. Most often, POS and maximum (instantaneous) volumetric air flow rates at the moment of exhalation are determined as 25, 50, 75% FVC. They are called respectively indicators MOS 25, MOS 50, MOS 75. The definition of FVC 1 is also popular - the volume of forced expiration for a time equal to 1 e. Based on this indicator, the Tiffno index (indicator) is calculated - the ratio of FVC 1 to FVC expressed as a percentage. A curve is also recorded that reflects the change in the volumetric velocity of the air flow during forced exhalation (Fig. 2.4). In this case, the volumetric velocity (l/s) is displayed on the vertical axis, and the percentage of exhaled FVC is displayed on the horizontal axis.

In the graph shown (Fig. 2, upper curve), the vertex indicates the value of PVC, the projection of the moment of exhalation of 25% FVC on the curve characterizes MVC 25, the projection of 50% and 75% FVC corresponds to the values ​​of MVC 50 and MVC 75. Not only flow velocities at individual points, but also the entire course of the curve are of diagnostic significance. Its part, corresponding to 0-25% of the exhaled FVC, reflects the air patency of the large bronchi, trachea, and the area from 50 to 85% of the FVC - the patency of the small bronchi and bronchioles. A deflection in the descending section of the lower curve in the expiratory region of 75-85% FVC indicates a decrease in the patency of the small bronchi and bronchioles.

Rice. 2. Stream breathing indicators. Note curves - the volume of a healthy person (upper), a patient with obstructive obstruction of the small bronchi (lower)

Determination of the listed volume and flow indicators is used in diagnosing the state of the external respiration system. To characterize the function of external respiration in the clinic, four variants of conclusions are used: normal, obstructive disorders, restrictive disorders, mixed disorders (a combination of obstructive and restrictive disorders).

For most flow and volume indicators of external respiration, deviations of their value from the proper (calculated) value by more than 20% are considered to be outside the norm.

Obstructive disorders- these are violations of the airway, leading to an increase in their aerodynamic resistance. Such disorders can develop as a result of increased tone of the smooth muscles of the lower respiratory tract, with hypertrophy or swelling of the mucous membranes (for example, with acute respiratory viral infections), accumulation of mucus, purulent discharge, in the presence of a tumor or foreign body, dysregulation of the patency of the upper respiratory tract and other cases.

The presence of obstructive changes in the airways is judged by a decrease in POS, FVC 1, MOS 25, MOS 50, MOS 75, MOS 25-75, MOS 75-85, the value of the Tiffno test index and MVL. The Tiffno test rate is normally 70-85%, a decrease to 60% is regarded as a sign of a moderate disorder, and to 40% as a pronounced disorder of bronchial obstruction. In addition, with obstructive disorders, indicators such as residual volume, functional residual capacity and total lung capacity increase.

Restrictive violations- this is a decrease in the expansion of the lungs when inhaling, a decrease in respiratory excursions of the lungs. These disorders can develop due to decreased compliance of the lungs, damage to the chest, the presence of adhesions, accumulation of fluid, purulent contents, blood in the pleural cavity, weakness of the respiratory muscles, impaired transmission of excitation at neuromuscular synapses and other reasons.

The presence of restrictive changes in the lungs is determined by a decrease in vital capacity (at least 20% of the proper value) and a decrease in the MVL (nonspecific indicator), as well as a decrease in lung compliance and, in some cases, an increase in the Tiffno test score (more than 85%). With restrictive disorders, total lung capacity, functional residual capacity, and residual volume are reduced.

The conclusion about mixed (obstructive and restrictive) disorders of the external respiration system is made with the simultaneous presence of changes in the above flow and volume indicators.

Lung volumes and capacities

Tidal volume - this is the volume of air that a person inhales and exhales in a calm state; in an adult it is 500 ml.

Inspiratory reserve volume- this is the maximum volume of air that a person can inhale after a quiet breath; its size is 1.5-1.8 liters.

Expiratory reserve volume - this is the maximum volume of air that a person can exhale after a quiet exhalation; this volume is 1-1.5 liters.

Residual volume - this is the volume of air that remains in the lungs after maximum exhalation; The residual volume is 1 -1.5 liters.

Rice. 3. Changes in tidal volume, pleural and alveolar pressure during lung ventilation

Vital capacity of the lungs(VC) is the maximum volume of air that a person can exhale after the deepest breath. Vital capacity includes inspiratory reserve volume, tidal volume and expiratory reserve volume. The vital capacity of the lungs is determined by a spirometer, and the method for determining it is called spirometry. Vital capacity in men is 4-5.5 l, and in women - 3-4.5 l. It is greater in a standing position than in a sitting or lying position. Physical training leads to an increase in vital capacity (Fig. 4).

Rice. 4. Spirogram of pulmonary volumes and capacities

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 and is equal to 2.5 liters.

Total lung capacity(OEL) - the volume of air in the lungs at the end of a full inspiration. TLC includes residual volume and vital capacity of the lungs.

Dead space is formed by air that is located in the airways and does not participate in gas exchange. When you inhale, the last portions of atmospheric air enter the dead space and, without changing its composition, leave it when you exhale. The dead space volume is about 150 ml, or approximately 1/3 of the tidal volume during quiet breathing. This means that out of 500 ml of inhaled air, only 350 ml enters the alveoli. By the end of a quiet exhalation, the alveoli contain about 2500 ml of air (FRC), so with each quiet breath, only 1/7 of the alveolar air is renewed.

A. Forced breathing is ensured by involving a number of additional muscles in the contraction; it is carried out with a large expenditure of energy, since in this case the inelastic resistance sharply increases. When inhaling, an auxiliary role is played by all the muscles attached to the bones of the shoulder girdle, skull or spine and capable of raising the ribs - these are the sternocleidomastoid, trapezius, both pectoral muscles, the levator scapulae muscle, the scalene muscle, the serratus anterior muscle. Forced exhalation is also carried out with additional direct energy expenditure, Firstly, as a result of contraction of the internal intercostal muscles. Their direction is opposite to the direction of the external intercostal muscles, therefore, as a result of their contraction, the ribs are lowered. Secondly, The most important auxiliary expiratory muscles are the abdominal muscles, with the contraction of which the ribs are lowered, and the abdominal organs are compressed and shifted upward along with the diaphragm. The serratus posterior muscles also contribute to forced exhalation. Naturally, during forced inhalation and exhalation, all the forces with the help of which calm breathing is carried out also act.

B. Breathing type depends on gender and type of work activity. Men have a mainly abdominal type of breathing, while women have a mainly thoracic type. In the case of predominantly physical work, and in women, a predominantly abdominal type of breathing is formed. The thoracic type of breathing is ensured mainly due to the work of the intercostal muscles. In the abdominal type, as a result of a powerful contraction of the diaphragm, the abdominal organs shift downward, so when inhaling, the stomach “protrudes.”

IN. Volumes ventilation lungs depend on the depth of inhalation and exhalation. Ventilation is the exchange of gases between atmospheric air and the lungs. Its intensity and essence are expressed in two concepts. Hyperventilation - voluntary increase in breathing, not related to the metabolic needs of the body, and hyperpnea, involuntary increased breathing due to the real needs of the body. A distinction is made between lung ventilation volumes and their capacities, while the term “capacity” is understood as a combination of several volumes (Fig. 7.5).

1. Tidal volume(DO) is the volume of air that a person inhales and exhales during quiet breathing, while the duration of one breathing cycle is 4-6 s, the act of inhalation is somewhat faster. This type of breathing is called eipnoe (good breathing).

2. Inspiratory reserve volume(PO inspiratory) - the maximum volume of air that a person can additionally inhale after a quiet inhalation.

3. Expiratory reserve volume(Exhalation RO) - the maximum volume of air that can be exhaled after a quiet exhalation.

4. Residual volume(00) - volume of air remaining in
lungs after maximum exhalation.

5. Vital capacity of the lungs(VC) is the largest volume of air that can be exhaled after a maximum inhalation. In young people, the proper value of vital capacity can be calculated using the formula: vital capacity = Height (m) 2.5 l.

6. Functional residual capacity(FRC) - the amount of air remaining in the lungs after a quiet exhalation is equal to the sum of the residual volume and the expiratory reserve volume.

7. Total lung capacity(VEL) - the volume of air contained in the lungs at the height of maximum inspiration is equal to the sum of vital capacity plus the residual volume. Total lung capacity, like other volumes and capacities, is highly variable and depends on gender, age and height. So, in young people aged 20-30 years it is on average 6 liters, in men aged 50-60 years it is on average about 5.5 liters.

In the case of pneumothorax, most of the residual air escapes, leaving the so-called minimum air volume. This air is retained in the so-called air traps, since part of the bronchioles collapses before the alveoli (the terminal and respiratory bronchioles do not contain cartilage). Therefore, the lung of an adult and a breathing newborn child does not sink in water (a test to determine by forensic examination whether a child was born alive: the lung of a stillborn drowns in water because it does not contain air).

Minute air volume(MOV) is the volume of air passing through the lungs in 1 minute. It is 6-8 liters at rest, the respiratory rate is 14-18 per minute. With intense muscle load, the ROM can reach 100 liters.

Maximum ventilation(MVL) is the volume of air that passes through the lungs in 1 minute at the maximum possible depth and frequency of breathing. MVL can reach 120-150 l/min in a young person, and 180 l/min in athletes, it depends on age, height, and gender. All other things being equal, MVL characterizes the patency of the airways, as well as the elasticity of the chest and the compliance of the lungs.

G. The question of how to breathe when the body’s need for gas exchange increases is often discussed: less often, but deeper or more often, but less deeply? Deep breathing is more effective for gas exchange in the lungs, since some of the air can flow convectively directly into the alveoli. However, it becomes difficult to breathe deeply during intense muscle activity, as inelastic resistance (aerodynamic resistance of the airways, viscous tissue resistance and inertial resistance) increases greatly. Therefore, with forced breathing, energy consumption to ensure the work of the external respiratory system increases from 2% of the total consumption at rest to 20% during heavy physical work. At the same time, in trained individuals, the increase in ventilation of the lungs during physical activity is carried out mainly due to deepening of breathing, and in untrained individuals - mainly due to increased breathing up to 40-50 per minute. However, usually the frequency and depth of breathing are determined by the physical activity itself. The body independently (non-produced)

voluntarily) sets the breathing mode according to his physical capabilities and needs at the moment. In addition, during intense physical work, a person often unnoticed switches from nasal breathing to mouth breathing, since nasal breathing creates approximately half the resistance to air flow. The conscious desire to breathe less often, but deeper during intense physical activity also leads to an increase in muscle work to overcome the increasing ETL during deep inspiration. Thus, less work of breathing is done with shallow, rapid breathing, although ventilation of the lungs is better with deep breathing. The beneficial result for the body is greater with shallow, frequent breathing. The breathing pattern is established involuntarily both during physical work and at rest. A person usually does not consciously (voluntarily) control the frequency and depth of breathing, although this is possible.

D. Alveolar ventilation convective route (direct intake of fresh air into the alveoli) occurs only during very intense physical work. Much more often, ventilation of the alveoli is carried out by diffusion. This is explained by the fact that repeated dichotomous division of bronchioles leads to an increase in the total cross-section of the airway in the distal direction and, naturally, to an increase in its volume. The time of gas diffusion in the gas exchange area and equalization of the composition of the gas mixture in the alveolar ducts and alveoli is about 1 s. The composition of gases in the transition zone approaches that of the alveolar ducts in approximately the same time - 1 s.