Human lung capacity - measurement of lung volumes. Dynamic breathing indicators Residual volume is

Indicators of pulmonary ventilation largely depend on the constitution, physical training, height, body weight, gender and age of a person, so the data obtained must be compared with the so-called proper values. The proper values are calculated using special nomograms and formulas, which are based on the determination of the proper basal metabolism. Many functional research methods have been reduced to a certain standard scope over time.

Lung volume measurement

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 equal to the sum of the reserve volumes of inhalation and exhalation and tidal volume (on average 3700 ml) and is the volume of air that a person is able to exhale during the deepest exhalation after a maximum inhalation.

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).

Spirography of the lungs

Lung spirography allows you to obtain the most reliable data. In addition to measuring lung volumes, using a spirograph you can obtain a number of additional indicators (tidal and minute ventilation volumes, etc.). The data is recorded in the form of a spirogram, from which one can judge the norm and pathology.

Study of pulmonary ventilation intensity

Minute breathing volume

The minute volume of breathing is determined by multiplying the tidal volume by the respiratory frequency, on average it is 5000 ml. More accurately determined using spirography.

Maximum ventilation

Maximum ventilation of the lungs ("breathing limit") is the amount of air that can be ventilated by the lungs at maximum tension of the respiratory system. Determined by spirometry with maximum deep breathing with a frequency of about 50 per minute, normally 80 - 200 ml.

Breathing reserve

The respiratory reserve reflects the functionality of the human respiratory system. In a healthy person it is equal to 85% of the maximum ventilation of the lungs, and with respiratory failure it decreases to 60 - 55% and lower.

All these tests make it possible to study the state of pulmonary ventilation, its reserves, the need for which may arise when performing heavy physical work or in case of respiratory disease.

Study of the mechanics of the respiratory act

This method allows you to determine the ratio of inhalation and exhalation, respiratory effort in different phases of breathing.

EFZHEL

Expiratory forced vital capacity (EFVC) is examined according to Votchal - Tiffno. It is measured in the same way as when determining vital capacity, but with the fastest, forced exhalation. In healthy individuals, it is 8-11% less than vital capacity, mainly due to an increase in resistance to air flow in the small bronchi. In a number of diseases accompanied by an increase in resistance in the small bronchi, for example, broncho-obstructive syndromes, pulmonary emphysema, EFVC changes.

IFZHEL

Inspiratory forced vital capacity (IFVC) is determined with the fastest possible forced inspiration. It does not change with emphysema, but decreases with airway obstruction.

Pneumotachometry

Pneumotachometry evaluates the change in “peak” air flow velocities during forced inhalation and exhalation. It allows you to assess the state of bronchial obstruction. ###Pneumotachography

Pneumotachography is carried out using a pneumotachograph, which records the movement of an air stream.

Tests to detect obvious or hidden respiratory failure

Based on the determination of oxygen consumption and oxygen deficiency using spirography and ergospirography. This method can determine oxygen consumption and oxygen deficiency in a patient when he performs a certain physical activity and at rest.

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

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

The function of breathing in humans is realized by:

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

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

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

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

Lung capacity

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

Total capacity = Vital capacity + Residual volume

Vital capacity makes up three lung volumes:

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

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

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

functional residual capacity = Expiratory reserve volume + Residual volume

Fig.8.1. Lung volumes and capacities.

One of the main characteristics of external respiration is the minute volume of respiration (MVR). Ventilation is determined by the volume of air inhaled or exhaled per unit of time. MVR is the product of tidal volume and the frequency of respiratory cycles. Normally, at rest, DO is 500 ml, the frequency of respiratory cycles is 12 - 16 per minute, hence the MOD is 6 - 7 l/min. Maximum ventilation is the volume of air that passes through the lungs in 1 minute during the maximum frequency and depth of respiratory movements.

Alveolar ventilation

So, external breathing, or ventilation of the lungs, ensures that approximately 500 ml of air enters the lungs during each inspiration (BEFORE). Saturation of blood with oxygen and removal of carbon dioxide occurs when contact of the blood of the pulmonary capillaries with the air contained in the alveoli. Alveolar air is the internal gas environment of the body of mammals and humans. Its parameters - oxygen and carbon dioxide content - are constant. The amount of alveolar air approximately corresponds to the functional residual capacity of the lungs - the amount of air that remains in the lungs after a quiet exhalation, and is normally equal to 2500 ml. It is this alveolar air that is renewed by atmospheric air entering through the respiratory tract. It should be borne in mind that not all of the inhaled air participates in pulmonary gas exchange, but only that part of it that reaches the alveoli. Therefore, to assess the effectiveness of pulmonary gas exchange, it is not so much pulmonary ventilation that is important, but alveolar ventilation.

As is known, part of the tidal volume does not participate in gas exchange, filling the anatomically dead space of the respiratory tract - approximately 140 - 150 ml.

In addition, there are alveoli, which are currently ventilated, but not supplied with blood. This part of the alveoli is the alveolar dead space. The sum of anatomical and alveolar dead space is called functional or physiological dead space. Approximately 1/3 of the tidal volume is due to the ventilation of dead space filled with air that is not directly involved in gas exchange and only moves in the lumen of the airways during inhalation and exhalation. Therefore, ventilation of the alveolar spaces—alveolar ventilation—is pulmonary ventilation minus dead space ventilation. Normally, alveolar ventilation is 70 - 75% of the MOD value.

Calculation of alveolar ventilation is carried out according to the formula: MAV = (DO - MP)  RR, where MAV is minute alveolar ventilation, DO - tidal volume, MP - dead space volume, RR - respiratory rate.

Figure 6. Correlation between MOP and alveolar ventilation

We use these data to calculate another value characterizing alveolar ventilation - alveolar ventilation coefficient . This coefficient shows how much of the alveolar air is renewed with each breath. By the end of a quiet exhalation, there is about 2500 ml of air (FRC) in the alveoli; during inhalation, 350 ml of air enters the alveoli, therefore, only 1/7 of the alveolar air is renewed (2500/350 = 7/1).

Ventilation- This is the exchange of gases between the alveolar air and the lungs. A quantitative characteristic of pulmonary ventilation is the minute volume of respiration (MVR) - the volume of air passing through the lungs in 1 minute. You can determine the MOD if you know the frequency of respiratory movements (at rest in an adult it is 16-20 per 1 minute) and tidal volume (DO = 350 - 800 ml).

MOD=RR´DO = 5000 -16000 ml/min

However, not all of the ventilated air participates in pulmonary gas exchange, but only that part of it that reaches the alveoli. The fact is that approximately 1/3 of the tidal volume at rest falls on the ventilation of the so-called anatomical dead space (MF), filled with air, which does not directly participate in gas exchange and only moves in the lumen of the airways during inhalation and exhalation. But sometimes some of the alveoli do not function or function partially due to the absence or reduction of blood flow in the nearby capillaries. From a functional point of view, these alveoli also represent dead space. When the alveolar dead space is included in the general dead space, the latter is called not anatomical, but physiological dead space. In a healthy person, the anatomical and physiological spaces are almost equal, but if part of the alveoli does not function or functions only partially, the volume of physiological dead space may be several times greater than the anatomical one.

Therefore, ventilation of the alveolar spaces is alveolar ventilation (AV) - represents pulmonary ventilation minus dead space ventilation.

AB= BH´(DO –MP)

The intensity of alveolar ventilation depends on the depth of breathing: the deeper the breathing (more DO), the more intense the ventilation of the alveoli.

Maximum ventilation (MVV)- the volume of air that passes through the lungs in 1 minute during the maximum frequency and depth of respiratory movements. Maximum ventilation occurs during intense work, with a lack of O 2 (hypoxia) and an excess of CO 2 (hypercapnia) in the inhaled air. Under these conditions, MOR can reach 150 - 200 liters per minute.

The indicators listed above are dynamic and reflect the efficiency of the respiratory system in a time aspect (usually within 1 minute).

In addition to dynamic indicators, external respiration is assessed by static indicators (Fig. 7):

§ tidal volume (TO) - this is the volume of air inhaled and exhaled during quiet breathing (in an adult it is 350 - 800 ml);

§ inspiratory reserve volume (IRV)– additional volume of air that can be inhaled beyond a quiet inhalation during forced breathing (PO vd on average 1500-2500 ml);

§ expiratory reserve volume (ERV)– the maximum additional volume of air that can be exhaled after a quiet exhalation (PO exhalation on average 1000-1500 ml);

§ residual lung volume (00) - volume of air that remains in the lungs after maximum exhalation (OO = 1000 -1500 ml)

Fig.7. Spirogram for quiet and forced breathing

When the lungs collapse (pneumothorax), most of the residual air escapes ( collapse residual volume = 800-1000 ml), and remains in the lungs minimum residual volume(200-400 ml). 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). This knowledge is used in forensic medicine to test whether a child was born alive: the lung of a stillborn drowns in water because it contains no air.

The sums of lung volumes are called lung capacities.

The following lung capacities are distinguished:

1. total lung capacity (TLC)- the volume of air in the lungs after maximum inspiration - includes all four volumes

2. vital capacity of the lungs (VC) includes tidal volume, inspiratory reserve volume, expiratory reserve volume. Vital capacity is the volume of air exhaled from the lungs after maximum inhalation with maximum exhalation.

Vital = DO + ROvd + ROvyd

Vital vital capacity is 3.5 - 5.0 l in men, 3.0-4.0 l in women. The value of vital capacity depends on height, age, gender, and the degree of functional training.

With age, this figure 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 vital capacity on average 25% less than men. Vital vital capacity depends on height, since the size of the chest is proportional to other body dimensions. VC depends on the degree of training: VC is especially high (up to 8 l) in swimmers and rowers, since these athletes have well-developed auxiliary muscles (pectoralis major and minor).

3. inspiratory capacity (Evd) equal to the sum of tidal volume and inspiratory reserve volume, averages 2.0 - 2.5 l;

4. functional residual capacity (FRC)- volume of air in the lungs after a quiet exhalation. During quiet inhalation and exhalation, the lungs constantly contain approximately 2500 ml of air, filling the alveoli and lower respiratory tract. Thanks to this, the gas composition of the alveolar air is maintained at a constant level.

In a routine study, TLC, OO and FRC are not available for measurement. They are determined using gas analyzers, studying changes in the composition of gas mixtures in a closed loop (helium, nitrogen content).

To assess the ventilation function of the lungs, the condition of the respiratory tract, and study the breathing pattern (pattern), various research methods are used: pneumography, spirometry, spirography.

Spirography (Latin spiro breathe + Greek graphо write, depict)- a method of graphically recording changes in lung volumes during natural respiratory movements and volitional forced respiratory maneuvers.

Spirography allows you to obtain a number of indicators that describe lung ventilation.

In technical terms, all spirographs are divided into open and closed type devices (Fig. 8).

Rice. 8. Schematic representation of a spirograph

In open-type devices, the patient inhales atmospheric air through a valve box, and the exhaled air enters a Douglas bag or a Tiso spirometer (capacity 100-200 l), sometimes to a gas meter, which continuously determines its volume. The air collected in this way is analyzed: the values of oxygen absorption and carbon dioxide release per unit of time are determined. Closed-type devices use the air from the bell of the device, circulating in a closed circuit without communication with the atmosphere. Exhaled carbon dioxide is absorbed by a special absorber.

Modern devices that record changes in lung volume during breathing (both open and closed types) have electronic computing devices for automatic processing of measurement results.

When analyzing a spirogram, speed indicators are also determined. Calculation of speed indicators is of great importance in identifying signs of bronchial obstruction.

§ Forced expiratory volume in 1 s(FEV1) - the volume of air expelled with maximum effort from the lungs during the first second of exhalation after a deep inhalation, i.e. part of the FVC exhaled in the first second. FEV1 primarily reflects the condition of the large airways and is often expressed as a percentage of VC (normal FEV1 = 75% VC).

§ Tiffno index – FEV1/FVC ratio, expressed in %:

IT= FEV1´ 100%

FVC

It is determined in the respiratory “push” test (Tiffno test) and consists of studying a single forced exhalation, allowing important diagnostic conclusions to be made about the functional state of the respiratory apparatus. At the end of exhalation, the intensity of the respiratory flow is limited due to compression of the small airways (Fig. 8).

Rice. 9. Schematic representation of the spirogram and its indicators

Forced expiratory volume in the first second (FEV1) is normally at least 70-75%. A decrease in the Tiffno index and FEV1 is a characteristic sign of diseases that are accompanied by a decrease in bronchial patency - bronchial asthma, chronic obstructive pulmonary disease, bronchiectasis, etc.

Using a spirogram you can determine oxygen volume, consumed by the body. If there is an oxygen compensation system in the spirograph, this indicator is determined by the slope of the curve of oxygen entering it; in the absence of such a system, by the slope of the spirogram of quiet breathing. Dividing this volume by the number of minutes during which oxygen consumption was recorded gives the value VО 2(is 200-400 ml at rest).

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.

for men JEL = 5.2xP - 0.029xB - 3.2

for women JEL = 4.9xP - 0.019xB - 3.76

for girls from 4 to 17 years old with height from 1.0 to 1.75 m:

JEL = 3.75xP - 3.15

for boys of the same age with a height of up to 1.65 m:

JEL = 4.53xP - 3.9, and with the growth of St. 1.65 m - JEL = 10xP - 12.85

where P is height (m), B is age

This comparison is expressed as a percentage relative to the proper indicator. Deviations exceeding 15-20% of the expected value are considered pathological.

Control questions

1. What is pulmonary ventilation, what indicator characterizes it?

2. What is anatomical and physiological dead space?

3. How to determine alveolar ventilation?

4. What is MVL?

5. What static indicators are used to assess external respiration?

6. What types of lung capacities are there?

7. On what factors does the value of vital capacity depend?

8. For what purpose is spirography used?

10. What are proper indicators, how are they determined?

Ventilator! If you understand it, it is equivalent to the appearance, as in the films, of a superhero (doctor) super weapons(if the doctor understands the intricacies of mechanical ventilation) against the death of the patient.

To understand mechanical ventilation you need basic knowledge: physiology = pathophysiology (obstruction or restriction) of breathing; main parts, structure of the ventilator; provision of gases (oxygen, atmospheric air, compressed gas) and dosing of gases; adsorbers; elimination of gases; breathing valves; breathing hoses; breathing bag; humidification system; breathing circuit (semi-closed, closed, semi-open, open), etc.

All ventilators provide ventilation by volume or pressure (no matter what they are called; depending on what mode the doctor has set). Basically, the doctor sets the mechanical ventilation mode for obstructive pulmonary diseases (or during anesthesia) by volume, during restriction by pressure.

The main types of ventilation are designated as follows:

CMV (Continuous mandatory ventilation) - Controlled (artificial) ventilation

VCV (Volume controlled ventilation) - volume controlled ventilation

PCV (Pressure controlled ventilation) - pressure controlled ventilation

IPPV (Intermittent positive pressure ventilation) - mechanical ventilation with intermittent positive pressure during inspiration

ZEEP (Zero endexpiratory pressure) - ventilation with pressure at the end of expiration equal to atmospheric

PEEP (Positive endexpiratory pressure) - Positive end expiratory pressure (PEEP)

CPPV (Continuous positive pressure ventilation) - ventilation with PDKV

IRV (Inversed ratio ventilation) - mechanical ventilation with a reverse (inverted) inhalation:exhalation ratio (from 2:1 to 4:1)

SIMV (Synchronized intermittent mandatory ventilation) - Synchronized intermittent mandatory ventilation = A combination of spontaneous and mechanical breathing, when, when the frequency of spontaneous breathing decreases to a certain value, with continued attempts to inhale, overcoming the level of the established trigger, mechanical breathing is synchronously activated

You should always look at the letters ..P.. or ..V.. If P (Pressure) means by distance, if V (Volume) by volume.

Vt – tidal volume,
f – respiratory rate, MV – minute ventilation
PEEP – PEEP = positive end expiratory pressure
Tinsp – inspiratory time;
Pmax - inspiratory pressure or maximum airway pressure.
Gas flow of oxygen and air.

Tidal volume(Vt, DO) set from 5 ml to 10 ml/kg (depending on the pathology, normal 7-8 ml per kg) = how much volume the patient should inhale at a time. But to do this, you need to find out the ideal (proper, predicted) body weight of a given patient using the formula (NB! remember):

Men: BMI (kg)=50+0.91 (height, cm – 152.4)

Women: BMI (kg)=45.5+0.91·(height, cm – 152.4).

Example: a man weighs 150 kg. This does not mean that we should set the tidal volume to 150kg·10ml= 1500 ml. First, we calculate BMI=50+0.91·(165cm-152.4)=50+0.91·12.6=50+11.466= 61,466 kg our patient should weigh. Imagine, oh allai deseishi! For a man with a weight of 150 kg and a height of 165 cm, we must set the tidal volume (TI) from 5 ml/kg (61.466·5=307.33 ml) to 10 ml/kg (61.466·10=614.66 ml) depending on pathology and extensibility of the lungs.

2. The second parameter that the doctor must set is breathing rate(f). The normal respiratory rate is 12 to 18 per minute at rest. And we don't know what frequency to set: 12 or 15, 18 or 13? To do this we must calculate due MOD (MV). Synonyms for minute breathing volume (MVR) = minute ventilation (MVL), maybe something else... This means how much air the patient needs (ml, l) per minute.

MOD=BMI kg:10+1

according to the Darbinyan formula (outdated formula, often leads to hyperventilation).

Or modern calculation: MOD=BMIkg·100.

(100%, or 120%-150% depending on the patient’s body temperature..., from the basal metabolism in short).

Example: The patient is a woman, weighs 82 kg, height is 176 cm. BMI = 45.5 + 0.91 (height, cm - 152.4) = 45.5 + 0.91 (176 cm - 152.4) = 45.5+0.91 23.6=45.5+21.476= 66,976 kg should weigh. MOD = 67 (rounded up immediately) 100 = 6700 ml or 6,7 liters per minute. Now only after these calculations can we find out the breathing frequency. f=MOD:UP TO=6700 ml: 536 ml=12.5 times per minute, which means 12 or 13 once.

3. Install REER. Normally (previously) 3-5 mbar. Now you can 8-10 mbar in patients with normal lungs.

4. The inhalation time in seconds is determined by the ratio of inhalation to exhalation: I: E=1:1,5-2 . In this parameter, knowledge about the respiratory cycle, ventilation-perfusion ratio, etc. will be useful.

5. Pmax, Pinsp peak pressure is set so as not to cause barotrauma or rupture the lungs. Normally, I think 16-25 mbar, depending on the elasticity of the lungs, the weight of the patient, the extensibility of the chest, etc. In my knowledge, lungs can rupture when Pinsp is more than 35-45 mbar.

6. The fraction of inhaled oxygen (FiO 2) should be no more than 55% in the inhaled respiratory mixture.

All calculations and knowledge are needed so that the patient has the following indicators: PaO 2 = 80-100 mm Hg; PaCO 2 =35-40 mm Hg. Just, oh allai deseishi!