Functional tests used to study external respiration. Functional tests of the respiratory system: what is it and why is it carried out

functional test- a method for determining the degree of influence on the body of dosed physical activity.

Breath- a process that ensures the consumption of oxygen and the release of carbon dioxide by the tissues of a living organism, impl. through the complex interaction of the respiratory, circulatory and blood systems.

External (pulmonary) respiration is the exchange of air between the environment and the lungs, intracellular (tissue) - the exchange of oxygen and carbon dioxide between the blood and body cells.

The Stange test (holding the breath on inspiration) characterizes the resistance of the body to a lack of oxygen. After 5 minutes of rest while sitting, take 2-3 deep breaths and exhale, and then, having taken a full breath, hold your breath, the time is noted from the moment the breath is held until it stops. The average indicator is the ability to hold your breath while inhaling for untrained people for 40-55 seconds, for trained people - for 60-90 seconds or more. With an increase in training, the breath holding time increases; in case of illness or overwork, this time decreases to 30-35 seconds.

Genchi test (breath holding on exhalation). It is performed in the same way as the Stange test, only the breath is held after a full exhalation. Here, the average indicator is the ability to hold the breath on exhalation for untrained people for 25-30 seconds, for trained people for 40-60 seconds or more.

Serkin test. After a 5-minute sitting rest, the breath holding time is determined while inhaling in a sitting position (first phase). In the second phase, 20 squats are performed in 30 seconds and holding the breath while standing is repeated. In the third phase, after resting while standing for one minute, the time of holding the breath while sitting is determined (the first phase is repeated).

17. Self-control of the level of development of physical. qualities: endurance and strength

Endurance- the ability to perform exercises for a long time without reducing their intensity. For self-control of general endurance, we recommend the most accessible, popular all over the world 12-minute running test, developed by the American doctor Cooper. During the test, you need to cover as much distance as possible. At the same time, it is not allowed to overexert yourself and, if you feel short of breath, you need to slow down the pace of running or switch to walking, and when breathing is restored, you can run again. It is advisable to carry out the test on a stadium treadmill, where it is easy to calculate the distance traveled.

Some idea of ​​the strength can be obtained by doing the following exercises:

Pulling up on the crossbar, bending the arms in the lying position to assess the strength of the muscles of the arms and shoulder girdle;

Raising the torso from a supine position to a sitting position (feet of the legs are fixed, hands behind the head) to assess the strength of the abdominal muscles;

Squatting on one leg, while the other leg and arms are extended forward ("pistol") to assess the strength of the leg muscles.

The criteria for assessing speed-strength abilities and strength endurance are: the number of pull-ups, push-ups; hang hold time; range of throws, jumps, etc.

About the speed-explosive strength of the muscles of the legs gives an idea of ​​a long jump from a place. The maximum strength of the pectoral and leg muscles can be determined by performing the following exercises: bench press and squat with a barbell on the shoulders.

18. Self-control of the level of development of physical. qualities: speed, flexibility, dexterity

To control the speed of an integral motor action, it is possible to use overcoming short distances at maximum speed (running 30, 60, 100 m).

To assess the maximum frequency of movements of the arms and legs, you can use the simplest forms of tapping tests at home.

The tapping test requires paper, a pencil and a stopwatch. On command, within 10 seconds, apply with the hand that is stronger for you, with a pencil, dots on paper with maximum frequency. Students have 60-70 points in 10 s.

Flexibility- mobility in various joints. depends on: elasticity of muscles and ligaments, external temperature, time of day. Testing should be carried out after an appropriate warm-up. The main tests of flexibility are simple control exercises: bends, "bridge", splits, squats, etc.

One of the most important indicators of flexibility is the mobility of the spine. Therefore, we recommend that you determine it first. To do this, you need to stand on a stool and lean forward to the limit, without bending your knees and lowering your arms. The distance from the end of the middle finger of the hand to the platform on which you are standing is measured. If you reach the platform with your fingers, then the mobility of the spine is satisfactory. If the fingers are below zero when tilted, the mobility is assessed as good and a plus sign is placed (for example, +5 cm). If the fingers do not reach the horizontal plane, then the mobility of the spine is assessed as insufficient.

Functional tests to assess the state of the cardiovascular system.

Blood circulation is one of the most important physiological processes that maintain homeostasis, ensure the continuous delivery of nutrients and oxygen necessary for life to all organs and cells of the body, the removal of carbon dioxide and other metabolic products, the processes of immunological protection and humoral (fluid) regulation of physiological functions. The level of the functional state of the cardiovascular system can be assessed using various functional tests.

Single test. Before performing a one-stage test, they rest while standing, without moving for 3 minutes. Then measure the heart rate for one minute. Then 20 deep squats are performed in 30 seconds from the initial position of the legs shoulder-width apart, arms along the body. When squatting, the arms are brought forward, and when straightened, they are returned to their original position. After performing squats, the heart rate is calculated for one minute. When assessing, the magnitude of the increase in heart rate after exercise is determined in percent. A value of up to 20% means an excellent response of the cardiovascular system to the load, from 21 to 40% - good; from 41 to 65% - satisfactory; from 66 to 75% - bad; from 76 and more - very bad.

Ruffier index. To assess the activity of the cardiovascular system, you can use the Ryuffier test. After a 5-minute calm state in a sitting position, count the pulse for 10 seconds (P1), then perform 30 squats within 45 seconds. Immediately after squats, count the pulse for the first 10 s (P2) and one minute (P3) after the load. The results are evaluated by the index, which is determined by the formula:

Ruffier index \u003d 6x (P1 + P2 + R3) -200

Assessment of cardiac performance: Ruffier index

0.1-5 - "excellent" (very good heart)

5.1 - 10 - "good" (good heart)

10.1 - 15 - "satisfactory" (heart failure)

15.1 - 20 - "poor" (severe heart failure)

Respiration is a process that provides the consumption of oxygen and the release of carbon dioxide by the tissues of a living organism.

There are external (pulmonary) and intracellular (tissue) respiration. External respiration is the exchange of air between the environment and the lungs, intracellular - the exchange of oxygen and carbon dioxide between the blood and body cells. To determine the state of the respiratory system and the ability of the internal environment of the body to be saturated with oxygen, the following tests are used.

Stange's test (holding the breath on inspiration). After 5 minutes of sitting rest, take 2-3 deep breaths and exhale, and then, having taken a full breath, hold your breath, the time is noted from the moment of holding the breath until it stops.

The average indicator is the ability to hold your breath while inhaling for untrained people for 40-55 seconds, for trained people - for 60-90 seconds or more. With an increase in training, the breath holding time increases; in case of illness or overwork, this time decreases to 30-35 seconds.

Genchi test (breath holding on exhalation). It is performed in the same way as the Stange test, only the breath is held after a full exhalation. Here, the average indicator is the ability to hold the breath on exhalation for untrained people for 25-30 seconds, for trained people for 40-60 seconds and

Serkin test. After a 5-minute sitting rest, the breath holding time is determined while inhaling in a sitting position (first phase). In the second phase, 20 squats are performed in 30 seconds. and holding the breath while inhaling while standing is repeated. In the third phase, after resting while standing for one minute, the time of holding the breath while sitting is determined (the first phase is repeated)

Stange test. The examinee in a sitting position takes a deep breath and exhale, and then inhale and hold his breath. Normally, the Stange test is 40-60 seconds for non-athletes, 90-120 seconds for athletes.

Genchi test. The examinee in a sitting position takes a deep breath, then an incomplete exhalation and holds his breath. Normally, the test is -20-40 seconds (non-athletes), 40-60 seconds (athletes). Rosenthal test. Five measurements of VC at 15-sec intervals. In N, all VCs are the same.

Serkin test. It is carried out in three stages. 1st phase: holding the breath while inhaling in a sitting position; 2nd phase: holding the breath while inhaling after 20 squats in 30 seconds, 3rd phase: a minute later, repetition of the 1st phase. This is a test of endurance. For a healthy trained person 1st phase = 45-60 sec; 2nd phase = more than 50% of 1st phase; 3rd phase = 100% or more 1st phase. For a healthy untrained person: 1st phase = 35-45 sec; 2nd phase = 30-50% of the 1st phase; 3rd phase = 70-100% of 1st phase. With latent circulatory failure: 1st phase = 20-30 sec, 2nd phase = less than 30% of 1st phase; 3rd phase = less than 70% of 1st phase.

Functional tests to assess the state of the cardiovascular system Martinet-Kushelevsky test (with 20 squats)

After a 10-minute rest in a sitting position, the subject's pulse is counted every 10 seconds up to 3 times obtaining the same numbers. Next, blood pressure and respiratory rate are measured. All found values ​​are initial. Then the subject does 20 deep squats, with arms thrown forward, for 30 s (under a metronome). After squats, the subject sits down; the first 10 seconds from the 1st minute of the recovery period, count the pulse, and in the remaining 50 seconds, measure blood pressure. First, the 2nd minute of the recovery period for 10-second segments determine the pulse to 3-fold repetition of the original values. At the end of the test, blood pressure is measured. Sometimes in the recovery period there may be a decrease in the pulse below the initial data ("negative phase"). If the "negative phase" of the pulse is short (10-30 seconds), then the reaction of the cardiovascular system to the load is normotonic.

The evaluation of the results of the test is carried out according to the pulse, blood pressure and the duration of the recovery period. Normotonic reaction: increased heart rate up to 16-20 beats in 10 s (by 60-80% of the original), SBP increases by 10-30 mm Hg (no more than 150% of the original), DBP remains constant or decreases by 5 -10 mmHg

Atypical reactions : hypotonic, hypertonic, dystonic, stepped.

Atypical reactions. Hypertensive- a significant increase in SBP (up to 200-220 mm Hg) and DBP, pulse up to 170-180 beats / min. This type of reaction occurs in the elderly, in the initial stages of hypertension, with physical overstrain of the cardiovascular system.

Hypotonic- a slight increase in blood pressure with a very significant increase in heart rate up to 170-180 beats / min, the recovery period increases to 5 minutes after the first load. This type of reaction is observed with VVD, after infectious diseases, with overwork.

Dystonic- a sharp decrease in DBP until the phenomenon of "infinite" tone appears (with a change in vascular tone). The appearance of this phenomenon in healthy athletes indicates a high contractility of the myocardium, but it can be. This type of reaction occurs with VVD, physical overstrain, in adolescents in the puberty period.

Stepped - SBP rises for 2-3 minutes of the recovery period. Such a CCC reaction occurs when there is a violation of the regulation of blood circulation and may be associated with insufficiently rapid redistribution of blood from the vessels of the internal organs to the periphery. Most often, such a reaction is noted after a 15-second run with overtraining.

CombinedPRob Letunova

The test includes 3 loads: 1) 20 sit-ups for 30 seconds, 2) 15-second run, 3) running in place for 3 minutes at a pace of 180 steps per minute. The first load is a warm-up, the second reveals the ability to quickly increase blood circulation, and the third reveals the body's ability to sustainably maintain increased blood circulation at a high level for a relatively long time. The types of response to physical activity are similar to the 20 squat test.

Ruffier test - quantitative assessment of the response of the pulse to a short-term load and the rate of recovery.

Methodology: after 5 minutes of rest in a sitting position, the pulse is counted for 10 seconds (recalculation for minutes - P0). Then the subject does 30 squats for 30 s, after which, in the sitting position, the pulse is determined for 10 s (P1). The third time the pulse is measured at the end of the first minute of the recovery period for 10 s (P2).

Ruffier index \u003d (P0 + P1 + P2 - 200) / 10

Evaluation of results: excellent - IR<0; хорошо – ИР 0-5, удовлетворительно – ИР 6-10, слабо – ИР 11-15;

unsatisfactory - IR > 15.

An indicator of the quality of the response of the cardiovascular system.

PCR \u003d (RD2 - RD1) : (P2 - P1) ( P1 - pulse at rest, WP1 - pulse pressure at rest, P2 - pulse after exercise, WP2 - pulse pressure after exercise) . Good functional state of the cardiovascular system with RCC = from 0.5 to 1.0.

All indicators of pulmonary ventilation are variable. They depend on sex, age, weight, height, body position, the state of the nervous system of the patient 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 sex - the so-called due indicators. Such a comparison is expressed as a percentage in relation to the due indicator. Deviations exceeding 15-20% of the value of the due indicator are considered pathological.

SPIROGRAPHY WITH REGISTRATION OF THE FLOW-VOLUME LOOP

Spirography with the registration of the "flow-volume" loop is a modern method for studying pulmonary ventilation, which consists in determining the volumetric velocity of the air flow in the inhalation tract and its graphical display in the form of a "flow-volume" loop with the patient's calm breathing and when he performs certain respiratory maneuvers . Abroad, this method is called spirometry . The aim of the study is to diagnose the type and degree of pulmonary ventilation disorders based on the analysis of quantitative and qualitative changes in spirographic parameters.

Indications and contraindications for the use of spirometry similar to those for classical spirography.

Methodology . The study is carried out in the morning, regardless of the meal. The patient is offered to close both nasal passages with a special clamp, take an individual sterilized mouthpiece into the mouth and tightly clasp it with the lips. The patient in the sitting position breathes through the tube in an open circuit, with little to no resistance to breathing

The procedure for performing respiratory maneuvers with registration of the "flow-volume" curve of forced breathing is identical to that which is performed when recording FVC during classical spirography. The patient should be explained that in the forced breathing test, exhale into the device as if it were necessary to extinguish candles on a birthday cake. After a period of calm breathing, the patient takes the deepest possible breath, as a result of which an elliptical curve is recorded (curve AEB). Then the patient makes the fastest and most intense forced exhalation. At the same time, a curve of a characteristic shape is recorded, which in healthy people resembles a triangle (Fig. 4).

Rice. 4. Normal loop (curve) of the ratio of volumetric flow rate and air volume during respiratory maneuvers. Inhalation begins at point A, exhalation - at point B. POS is recorded at point C. The maximum expiratory flow in the middle of the FVC corresponds to point D, the maximum inspiratory flow - to point E

The maximum expiratory volumetric airflow rate is displayed by the initial part of the curve (point C, where the peak expiratory volumetric velocity is recorded - POSVVV) - After that, the volumetric flow rate decreases (point D, where MOC50 is recorded), and the curve returns to its original position (point A). In this case, the "flow-volume" curve describes the relationship between the volumetric airflow rate and lung volume (lung capacity) during respiratory movements.

The data of speeds and volumes of air flow are processed by a personal computer thanks to adapted software. The "flow-volume" curve is then displayed on the monitor screen and can be printed on paper, stored on magnetic media or in the memory of a personal computer.

Modern devices work with spirographic sensors in an open system with the subsequent integration of the air flow signal to obtain synchronous values ​​of lung volumes. Computer-calculated test results are printed along with the flow-volume curve on paper in absolute terms and as percentages of the proper values. In this case, FVC (air volume) is plotted on the abscissa axis, and the air flow measured in liters per second (l/s) is plotted on the ordinate axis (Fig. 5).

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Surname:

Name:

Ident. number: 4132

Date of birth: 01/11/1957

Age: 47 Years

Gender: female

Weight: 70 kg

Height: 165.0 cm

Rice. Fig. 5. Curve "flow-volume" of forced breathing and indicators of pulmonary ventilation in a healthy person

Rice. 6 Scheme of the FVC spirogram and the corresponding curve of forced expiration in the "flow-volume" coordinates: V - volume axis; V" - flow axis

The flow-volume loop is the first derivative of the classic spirogram. Although the flow-volume curve contains much of the same information as the classic spirogram, the visibility of the relationship between flow and volume allows a deeper insight into the functional characteristics of both the upper and lower airways (Fig. 6). The calculation of highly informative indicators MOS25, MOS50, MOS75 according to the classical spirogram has a number of technical difficulties when performing graphic images. Therefore, its results are not highly accurate. In this regard, it is better to determine these indicators from the flow-volume curve.
Assessment of changes in speed spirographic indicators is carried out according to the degree of their deviation from the proper value. As a rule, the value of the flow indicator is taken as the lower limit of the norm, which is 60% of the proper level.

BODIPLETHISMOGRAPHY

Body plethysmography is a method for studying the function of external respiration by comparing spirography indicators with indicators of mechanical fluctuations of the chest during the respiratory cycle. The method is based on the use of Boyle's law, which describes the constancy of the ratio of pressure (P) and volume (V) of gas in the case of a constant (constant) temperature:

P l V 1 \u003d P 2 V 2,

where R 1 - initial gas pressure; V 1 - initial volume of gas; P 2 - pressure after changing the volume of gas; V 2 - volume after changing the gas pressure.

Body plethysmography allows you to determine all volumes and capacities of the lungs, including those that are not determined by spirography. The latter include: residual volume of the lungs (ROL) - the volume of air (on average - 1000-1500 ml) remaining in the lungs after the deepest possible exhalation; functional residual capacity (FRC) - the volume of air remaining in the lungs after a quiet exhalation. Having determined these indicators, it is possible to calculate the total lung capacity (TLC), which is the sum of VC and TRL (see Fig. 2).

The same method determines such indicators as general and specific effective bronchial resistance, necessary to characterize bronchial obstruction.

Unlike previous methods of studying pulmonary ventilation, the results of body plethysmography are not associated with the patient's willpower and are the most objective.

Rice. 2.Schematic representation of the bodyplatysmography technique

Research methodology (Fig. 2). The patient is seated in a special closed hermetic cabin with a constant volume of air. He breathes through a mouthpiece connected to a breathing tube that is open to the atmosphere. Opening and closing of the breathing tube is performed automatically by an electronic device. During the study, the inhaled and exhaled air flow of the patient is measured using a spirograph. The movement of the chest during breathing causes a change in air pressure in the cabin, which is recorded by a special pressure sensor. The patient breathes calmly. This measures the airway resistance. At the end of one of the exhalations at the FFU level, the patient's breathing is briefly interrupted by closing the respiratory tube with a special plug, after which the patient makes several volitional attempts to inhale and exhale with the respiratory tube closed. In this case, the air (gas) contained in the patient's lungs is compressed on exhalation, and rarefied on inspiration. At this time, measurements are taken of the air pressure in the oral cavity (equivalent to alveolar pressure) and inside the chest volume of gas (display of pressure fluctuationsin a pressurized cabin). In accordance with the aforementioned Boyle's law, the calculation of functional residual lung capacity, other lung volumes and capacities, as well as indicators of bronchial resistance is carried out.

PEAKFLOWMETRY

Peakflowmetry- a method for determining how fast a person can exhale, in other words, this is a way to assess the degree of narrowing of the airways (bronchi). This examination method is important for people suffering from difficult exhalation, primarily for people diagnosed with bronchial asthma, COPD, and allows you to evaluate the effectiveness of the treatment and prevent an impending exacerbation.

Why Do you need a peak flow meter and how to use it?

When lung function is examined in patients, the peak, or maximum, rate at which the patient is able to exhale air from the lungs is invariably determined. In English, this indicator is called “peak flow”. Hence the name of the device - peak flowmeter. The maximum exhalation rate depends on many things, but most importantly, it shows how narrowed the bronchi are. It is very important that changes in this indicator go ahead of the patient's sensations. By noticing a decrease or increase in peak expiratory flow, he can take certain actions even before the state of health changes significantly.

The exchange of gases is carried out through the pulmonary membrane (the thickness of which is about 1 μm) by diffusion due to the difference in their partial pressure in the blood and alveoli (Table 2).

table 2

Values ​​of voltage and partial pressure of gases in body media (mm Hg)

Oxygen is found in the blood both in dissolved form and in the form of a combination with hemoglobin. However, the solubility of O 2 is very low: no more than 0.3 ml of O 2 can dissolve in 100 ml of plasma, therefore, hemoglobin plays the main role in oxygen transfer. 1 g of Hb attaches 1.34 ml of O 2, therefore, with a hemoglobin content of 150 g / l (15 g / 100 ml), every 100 ml of blood can carry 20.8 ml of oxygen. This so-called oxygen capacity of hemoglobin. Giving O 2 in the capillaries, oxyhemoglobin is converted into reduced hemoglobin. In the capillaries of tissues, hemoglobin is also able to form an unstable compound with CO 2 (carbohemoglobin). In the capillaries of the lungs, where the content of CO 2 is much less, carbon dioxide is separated from hemoglobin.

oxygen capacity of the blood includes the oxygen capacity of hemoglobin and the amount of O 2 dissolved in plasma.

Normally, 100 ml of arterial blood contains 19-20 ml of oxygen, and 100 ml of venous blood contains 13-15 ml.

Exchange of gases between blood and tissues. The oxygen utilization coefficient is the amount of O 2 that tissues consume, as a percentage of its total content in the blood. It is greatest in the myocardium - 40 - 60%. In the gray matter of the brain, the amount of oxygen consumed is approximately 8-10 times greater than in the white. In the cortical substance of the kidney, about 20 times more than in the internal parts of its medulla. Under severe physical exertion, the O2 utilization factor by the muscles and myocardium increases to 90%.

Oxyhemoglobin dissociation curve shows the dependence of hemoglobin saturation with oxygen on the partial pressure of the latter in the blood (Fig. 2). Since this curve is non-linear, the saturation of hemoglobin in arterial blood with oxygen occurs even at 70 mm Hg. Art. Saturation of hemoglobin with oxygen normally does not exceed 96 - 97%. Depending on the voltage of O 2 or CO 2 , increasing temperature, decreasing pH, the dissociation curve can shift to the right (which means less oxygen saturation) or to the left (which means more oxygen saturation).

Figure 2. Dissociation of oxyhemoglobin in the blood depending on the partial pressure of oxygen(and its displacement under the action of the main modulators) (Zinchuk, 2005, see 4):

sO 2 - saturation of hemoglobin with oxygen in%;

ro 2 - partial pressure of oxygen

The efficiency of oxygen uptake by tissues is characterized by the oxygen utilization factor (OUC). OMC is the ratio of the volume of oxygen absorbed by the tissue from the blood to the total volume of oxygen that enters the tissue with blood, per unit time. At rest, the AC is 30-40%, during exercise it increases to 50-60%, and in the heart it can increase to 70-80%.

FUNCTIONAL DIAGNOSIS METHODS

GAS EXCHANGE IN THE LUNGS

One of the important areas of modern medicine is non-invasive diagnostics. The urgency of the problem is due to gentle methodological methods of taking material for analysis, when the patient does not have to experience pain, physical and emotional discomfort; research safety due to the impossibility of infection with infections transmitted through blood or instruments. Non-invasive diagnostic methods can be used, on the one hand, on an outpatient basis, which ensures their wide distribution; on the other hand, in patients in the intensive care unit, because the severity of the patient's condition is not a contraindication for their implementation. Recently, interest in the study of exhaled air (EA) has increased in the world as a non-invasive method for diagnosing bronchopulmonary, cardiovascular, gastrointestinal and other diseases.

It is known that the functions of the lungs, in addition to respiratory, are metabolic and excretory. It is in the lungs that substances such as serotonin, acetylcholine and, to a lesser extent, noradrenaline undergo enzymatic transformation. The lungs have the most powerful enzyme system that destroys bradykinin (80% of bradykinin introduced into the pulmonary circulation is inactivated with a single passage of blood through the lungs). In the endothelium of the pulmonary vessels, thromboxane B2 and prostaglandins are synthesized, and 90-95% of prostaglandins of the E and F groups are also inactivated in the lungs. On the inner surface of the pulmonary capillaries, a large amount of angiotensin-converting enzyme is localized, which catalyzes the conversion of angiotensin I to angiotensin II. The lungs play an important role in the regulation of the aggregate state of the blood due to their ability to synthesize factors of the coagulation and anticoagulation systems (thromboplastin, factors VII, VIII, heparin). Volatile chemical compounds are released through the lungs, which are formed during metabolic reactions that occur both in the lung tissue and throughout the human body. So, for example, acetone is released in the oxidation of fats, ammonia and hydrogen sulfide - during the exchange of amino acids, saturated hydrocarbons - during the peroxidation of unsaturated fatty acids. By changing the amount and ratio of substances released during breathing, conclusions can be drawn about changes in metabolism and the presence of the disease.

Since ancient times, for the diagnosis of diseases, the composition of aromatic volatile substances emitted by the patient during breathing and through the skin (ie, odors emanating from the patient) was taken into account. Continuing the traditions of ancient medicine, the famous clinician of the early twentieth century M.Ya. Mudrov wrote: “Let your sense of smell be sensitive not to the suit of incense for your hair, not to the aromas that evaporate from your clothes, but to the locked and fetid air surrounding the patient, to his contagious breath, sweat and to all his eruptions” . The analysis of aromatic chemicals secreted by humans is so important for diagnosis that many odors are described as pathognomonic symptoms of diseases: for example, a sweetish “liver” odor (secretion of methyl mercaptan, a metabolite of methionine) in hepatic coma, the smell of acetone in a patient in ketoacidotic coma, or the smell of ammonia with uremia.

For a long period, the analysis of explosives was subjective and descriptive, but since 1784 a new stage has begun in its study - let's call it conditionally "paraclinical" or "laboratory". This year, French naturalist Antoine Laurent Lavoisier, together with the famous physicist and mathematician Simon Laplace, conducted the first laboratory study of exhaled air in guinea pigs. They established that the exhaled air consists of an asphyxiating part, which gives carbonic acid, and an inert part, which leaves the lungs unchanged. These parts were later named carbon dioxide and nitrogen. “Of all the phenomena of life, there is nothing more striking and deserving of attention than breathing,” wrote A.L. Lavoisier.

For a long time (XVIII–XIX centuries), the analysis of explosives was carried out by chemical methods. The concentrations of substances in explosives are low; therefore, to detect them, it was necessary to pass large volumes of air through absorbers and solutions.

In the middle of the 19th century, the German physician A. Nebeltau was the first to use the study of explosives to diagnose a disease - in particular, carbohydrate metabolism disorders. He developed a method for determining low concentrations of acetone in explosives. The patient was asked to exhale into a tube immersed in sodium iodate solution. Acetone contained in the air reduced iodine, while changing the color of the solution, according to which A. Nebeltau quite accurately determined the concentration of acetone.

At the end of XI In the 10th - early 20th centuries, the number of studies on the composition of explosives increased dramatically, which was primarily due to the needs of the military-industrial complex. In 1914, the first submarine Loligo was launched in Germany, which stimulated the search for new ways to obtain artificial air for breathing under water. Fritz Haber, developing chemical weapons (the first poison gases) since the autumn of 1914, was simultaneously developing a protective mask with a filter. The first gas attack on the fronts of the First World War on April 22, 1915 led to the invention of the gas mask in the same year. The development of aviation and artillery was accompanied by the construction of air-raid shelters with forced ventilation. Subsequently, the invention of nuclear weapons stimulated the design of bunkers for long stays in nuclear winter conditions, and the development of space science required the creation of new generations of life support systems with an artificial atmosphere. All these tasks of developing technical devices that ensure normal breathing in confined spaces could be solved only if the composition of the inhaled and exhaled air was studied. This is the situation when "there would be no happiness, but misfortune helped." In addition to carbon dioxide, oxygen and nitrogen, water vapor, acetone, ethane, ammonia, hydrogen sulfide, carbon monoxide and some other substances were found in explosives. Anstie isolated ethanol in explosives in 1874, a method still used in the breath test for alcohol today.

But a qualitative breakthrough in the study of the composition of explosives was made only at the beginning of the 20th century, when mass spectrography (MS) (Thompson, 1912) and chromatography began to be used. These analytical methods allowed the determination of substances at low concentrations and did not require large volumes of air to perform the analysis. Chromatography was first applied by the Russian botanist Mikhail Semenovich Tsvet in 1900, but the method was undeservedly forgotten and practically did not develop until the 1930s. The revival of chromatography is associated with the names of the English scientists Archer Martin and Richard Sing, who in 1941 developed the method of partition chromatography, for which they were awarded the Nobel Prize in chemistry in 1952. From the middle of the 20th century to the present day, chromatography and mass spectrography have been among the most widely used analytical methods for studying explosives. About 400 volatile metabolites, many of which are used as markers of inflammation, were determined in explosives by these methods, their specificity and sensitivity for the diagnosis of many diseases were determined. The description of the substances identified in the explosives in various nosological forms is inappropriate in this article, because even a simple listing of them would take many pages. With regard to the analysis of volatile substances in explosives, it is necessary to emphasize three points.

Firstly, the analysis of volatile substances of explosives has already “left” the laboratories and today is not only of scientific and theoretical interest, but also of purely practical importance. An example are capnographs (devices that record the level of carbon dioxide). Since 1943 (when Luft created the first device for recording CO 2 ), the capnograph has been an indispensable component of ventilators and anesthesia equipment. Another example is the determination of nitric oxide (NO). Its content in explosives was measured for the first time in 1991 by L. Gustafsson et al. in rabbits, guinea pigs and humans. Subsequently, it took one five years to prove the significance of this substance as a marker of inflammation. In 1996, a group of leading researchers created unified recommendations for the standardization of measurements and estimates of exhaled NO - Exhaled and nasal nitric oxide measurements: recommendations. And in 2003, FDA approval was obtained and commercial production of NO detectors began. In developed countries, the determination of nitric oxide in the IV is widely used in routine practice by pulmonologists, allergists as a marker of airway inflammation in steroid-naive patients and to assess the effectiveness of anti-inflammatory topical therapy in patients with chronic obstructive pulmonary diseases.

Secondly, the greatest diagnostic significance of the EV analysis was noted in respiratory diseases - significant changes in the composition of the EV in bronchial asthma, SARS, bronchiectasis, fibrosing alveolitis, tuberculosis, lung transplant rejection, sarcoidosis, chronic bronchitis, lung damage in systemic lupus erythematosus are described. , allergic rhinitis, etc.

Thirdly, in some nosological forms, the analysis of explosives makes it possible to detect pathology at a stage of development when other diagnostic methods are insensitive, nonspecific, and noninformative. For example, the detection of alkanes and monomethylated alkanes in EVs makes it possible to diagnose lung cancer at an early stage (Gordon et al., 1985), while standard screening studies for lung tumors (X-ray and sputum cytology) are not yet informative. The study of this problem was continued by Phillips et al., in 1999 they determined 22 volatile organic substances (mainly alkanes and benzene derivatives) in explosives, the content of which was significantly higher in patients with a lung tumor. Scientists from Italy (Diana Poli et al., 2005) showed the possibility of using styrenes (with a molecular weight of 10–12 M) and isoprenes (10–9 M) in explosives as biomarkers of the tumor process - the diagnosis was correctly established in 80% of patients.

Thus, the study of explosives continues quite actively in many areas, and the study of the literature on this issue gives us confidence that in the future, the analysis of explosives for diagnosing diseases will become as routine a method as controlling the level of alcohol in the explosives of a driver of a vehicle by a traffic police officer.

A new stage in the study of the properties of explosives began in the late 70s of the last century - the Nobel laureate Linus Pauling (Linus Pauling) proposed to analyze the condensate of explosives (KVV). Using the methods of gas and liquid chromatography, he was able to identify up to 250 substances, and modern techniques make it possible to determine up to 1000 (!) Substances in EQU.

From a physical point of view, an explosive is an aerosol consisting of a gaseous medium and liquid particles suspended in it. BB is saturated with water vapor, the amount of which is approximately 7 ml / kg of body weight per day. An adult excretes about 400 ml of water per day through the lungs, but the total amount of expiration depends on many external (humidity, environmental pressure) and internal (body condition) factors. So, in obstructive lung diseases (bronchial asthma, chronic obstructive bronchitis), the volume of expiration decreases, and in acute bronchitis, pneumonia, it increases; the hydroballast function of the lungs decreases with age - by 20% every 10 years, depends on physical activity, etc. Humidification of the EV is also determined by the bronchial circulation. Water vapor serves as a carrier for many volatile and non-volatile compounds through the dissolution of molecules (according to the dissolution coefficients) and the formation of new chemicals within the aerosol particle.

There are two main methods for the formation of aerosol particles:

1. Condensing- from small to large - the formation of liquid droplets from supersaturated vapor molecules.

2. Dispersion - from large to small - grinding of the bronchoalveolar fluid lining the respiratory tract, with turbulent air flow in the respiratory tract.

The average diameter of aerosol particles in normal conditions during normal breathing in an adult is 0.3 microns, and the number is 0.1–4 particles per 1 cm 2. When the air is cooled, water vapor and the substances contained in them condense, which makes their quantitative analysis possible.

Thus, the diagnostic capabilities of the study of CEA are based on the hypothesis that changes in the concentration of chemicals in the CEA, blood serum, lung tissue and bronchoalveolar lavage fluid are unidirectional.

To obtain CEA, both serial production devices (EcoScreen® - Jaeger Tonnies Hoechberg, Germany; R Tube® - Respiratory Research, Inc., USA) and self-made devices are used. The principle of operation of all devices is the same: the patient makes forced exhalations into a container (vessel, flask, tube), in which the water vapor contained in the air condenses when cooled. Cooling is carried out with liquid or dry ice, less often with liquid nitrogen. To improve the condensation of water vapor in the tank for collecting water, a turbulent air flow is created (a curved tube, a change in the diameter of the vessel). Such devices make it possible to collect up to 5 ml of condensate from older children and adults in 10–15 minutes of breathing. The collection of condensate does not require the active conscious participation of the patient, which makes it possible to use the technique from the neonatal period. For 45 minutes of calm breathing in newborns with pneumonia, it is possible to obtain 0.1–0.3 ml of condensate.

Most of the biologically active substances can be analyzed in the condensate collected with homemade devices.The exception is leukotrienes - given their rapid metabolism and instability, they can only be determined in frozen samples obtained with mass-produced instruments. For example, in the EcoScreen device, temperatures down to -10 ° C are created, which ensures rapid freezing of condensate.

The composition of the KVV can be influenced by the material from which the container is made. So, when studying lipid derivatives, the device should be made of polypropylene and it is recommended to avoid contact of KVV with polystyrene, which can absorb lipids, affecting the accuracy of measurements.

What kindbiomarkers are currently defined in the BHC? The most complete answer to this question can be found in the review by Montuschi Paolo (Department of Pharmacology, Faculty of Medicine, Catholic University of the Sacred Heart, Rome, Italy). The review was published in 2007 in Therapeutic Advances in Respiratory Disease, data are presented in Table. one.

Thus, exhaled air condensate is a biological medium, by changing the composition of which one can judge the morphofunctional state, primarily of the respiratory tract, as well as other body systems. The collection and study of condensate is a new promising area of ​​modern scientific research.

PULSE OXYMETRY

Pulse oximetry is the most accessible method for monitoring patients in many settings, especially with limited funding. It allows, with a certain skill, to evaluate several parameters of the patient's condition. After successful implementation in intensive care, awakening wards and during anesthesia, the method began to be used in other areas of medicine, for example, in general wards, where staff did not receive adequate training on how to use pulse oximetry. This method has its drawbacks and limitations, and in the hands of untrained personnel, situations that threaten the safety of the patient are possible. This article is intended just for the novice user of pulse oximetry.

A pulse oximeter measures the saturation of arterial hemoglobin with oxygen. The technology used is complex, but has two basic physical principles. First, the absorption by hemoglobin of light of two different wavelengths varies depending on its saturation with oxygen. Secondly, the light signal, passing through the tissues, becomes pulsating due to a change in the volume of the arterial bed with each contraction of the heart. This component can be separated by a microprocessor from non-pulsating, coming from the veins, capillaries and tissues.

Many factors affect the performance of a pulse oximeter. These may include external light, shivering, abnormal hemoglobin, pulse rate and rhythm, vasoconstriction, and cardiac activity. The pulse oximeter does not allow you to judge the quality of ventilation, but only shows the degree of oxygenation, which can give a false sense of security when inhaling oxygen. For example, there may be a delay in the onset of symptoms of hypoxia in airway obstruction. Nevertheless, oximetry is a very useful form of monitoring the cardiorespiratory system, increasing patient safety.

What does a pulse oximeter measure?

1. Saturation of hemoglobin in arterial blood with oxygen - the average amount of oxygen associated with each molecule of hemoglobin. The data is given as saturation percentage and an audible tone that changes in pitch with saturation.

2. Pulse rate - beats per minute for an average of 5-20 seconds.

The pulse oximeter does not provide information about:

? the oxygen content in the blood;

? the amount of oxygen dissolved in the blood;

? tidal volume, respiratory rate;

? cardiac output or blood pressure.

Systolic blood pressure can be judged by the appearance of a wave on the plethogram when the cuff is deflated for non-invasive pressure measurement.

Principles of modern pulse oximetry

Oxygen is transported in the bloodstream mainly in the form bound to hemoglobin. One hemoglobin molecule can carry 4 oxygen molecules and in this case it will be 100% saturated. The average percentage of saturation of a population of hemoglobin molecules in a certain volume of blood is the oxygen saturation of the blood. A very small amount of oxygen is carried dissolved in the blood, but is not measured by a pulse oximeter.

The relationship between the partial pressure of oxygen in arterial blood (PaO 2 ) and saturation is reflected in the hemoglobin dissociation curve (Fig. 1). The sigmoid shape of the curve reflects the unloading of oxygen in peripheral tissues, where PaO 2 is low. The curve can shift to the left or right under various conditions, for example, after a blood transfusion.

The pulse oximeter consists of a peripheral sensor, a microprocessor, a display showing the pulse curve, saturation value and pulse rate. Most devices have an audible tone, the pitch of which is proportional to saturation, which is very useful when the pulse oximeter display is not visible. The sensor is installed in the peripheral parts of the body, for example, on the fingers, earlobe or wing of the nose. The sensor contains two LEDs, one of which emits visible light in the red spectrum (660 nm), the other in the infrared spectrum (940 nm). Light passes through the tissues to the photodetector, while part of the radiation is absorbed by the blood and soft tissues, depending on the concentration of hemoglobin in them. The amount of light absorbed by each of the wavelengths depends on the degree of oxygenation of hemoglobin in the tissues.

The microprocessor is able to isolate the pulse component of the blood from the absorption spectrum, i.e. separate the arterial blood component from the permanent venous or capillary blood component. The latest generation of microprocessors are able to reduce the effect of light scattering on the performance of the pulse oximeter. The multiple time division of the signal is done by cycling the LEDs: red turns on, then infrared, then both turn off, and so many times per second, which eliminates background "noise". A new feature of microprocessors is quadratic multiple separation, in which the red and infrared signals are phase-separated and then recombined. With this option, interference from movement or electromagnetic radiation can be eliminated, since. they cannot occur in the same phase of two LED signals.

Saturation is calculated on average in 5-20 seconds. The pulse rate is calculated from the number of LED cycles and confident pulsing signals over a certain period of time.

PULSE OXIMETERAND I

According to the proportion of the absorbed light of each of the frequencies, the microprocessor calculates their coefficient. The pulse oximeter memory contains a series of oxygen saturation values ​​obtained in experiments on volunteers with a hypoxic gas mixture. The microprocessor compares the obtained absorption coefficient of the two wavelengths of light with the values ​​stored in the memory. Because It is unethical to reduce the oxygen saturation of volunteers below 70%, it must be recognized that the saturation value below 70% obtained from a pulse oximeter is not reliable.

Reflected pulse oximetry uses reflected light, so it can be used more proximal (for example, on the forearm or anterior abdominal wall), but in this case it will be difficult to fix the sensor. The principle of operation of such a pulse oximeter is the same as that of a transmission one.

Practical tips for using pulse oximetry:

The pulse oximeter must be kept constantly connected to the electrical network to charge the batteries;

Turn on the pulse oximeter and wait for it to perform a self-test;

Select the required sensor, suitable for the dimensions and for the selected installation conditions. The nail phalanges must be clean (remove the varnish);

Place the sensor on the selected finger, avoiding excessive pressure;

Wait a few seconds while the pulse oximeter detects the pulse and calculates the saturation;

Look at the pulse wave curve. Without it, any values ​​are insignificant;

Look at the pulse and saturation numbers that appear. Be careful when estimating them when their values ​​change quickly (for example, 99% suddenly changes to 85%). This is physiologically impossible;

Alarms:

If the "low oxygen saturation" alarm sounds, check the patient's consciousness (if it was originally). Check airway patency and adequacy of the patient's breathing. Raise your chin or use other airway management techniques. Give oxygen. Call for help.

If the “no pulse detected” alarm sounds, look at the pulse waveform on the pulse oximeter display. Feel the pulse on the central artery. In the absence of a pulse, call for help, start a cardiopulmonary resuscitation complex. If there is a pulse, change the position of the sensor.

On most pulse oximeters, you can change the saturation and pulse rate alarm limits to your liking. However, don't change them just to silence the alarm - it can tell you something important!

Using pulse oximetry

In the field, a simple portable all-in-one monitor that monitors saturation, heart rate, and rhythm regularity is best.

Safe non-invasive monitor of the cardio-respiratory status of critically ill patients in the intensive care unit, as well as during all types of anesthesia. Can be used for endoscopy when patients are sedated with midazolam. Pulse oximetry is more reliable than the best doctor in diagnosing cyanosis.

During transportation of the patient, especially in noisy conditions, for example, in an airplane, helicopter. The beep and alarm may not be heard, but the pulse waveform and saturation value provide general information about the cardio-respiratory status.

To assess the viability of limbs after plastic and orthopedic operations, vascular prosthetics. Pulse oximetry requires a pulsed signal, and thus helps determine if a limb is receiving blood.

Helps to reduce the frequency of blood sampling for gas analysis in patients in the intensive care unit, especially in pediatric practice.

Helps limit preterm infants from developing lung and retinal oxygen damage (saturation is maintained at 90%). Although pulse oximeters are calibrated against adult hemoglobin ( HbA ), absorption spectrum HbA and HbF identical in most cases, making the technique equally reliable in infants.

During thoracic anesthesia, when one of the lungs collapses, it helps to determine the effectiveness of oxygenation in the remaining lung.

Fetal oximetry is an evolving technique. Reflected oximetry, LEDs with a wavelength of 735 nm and 900 nm are used. The sensor is placed over the temple or cheek of the fetus. The sensor must be sterilizable. It is difficult to fix it, the data is not stable for physiological and technical reasons.

Limitation of pulse oximetry:

This is not a ventilation monitor.. Recent data draw attention to the false sense of security created by pulse oximeters in the anesthetist. An elderly woman in the awakening unit received oxygen through a mask. She began to progressively load, despite the fact that she had a saturation of 96%. The reason was that the respiratory rate and minute ventilation were low due to residual neuromuscular block, and the oxygen concentration in the exhaled air was very high. Eventually, the concentration of carbon dioxide in the arterial blood reached 280 mmHg (normal 40), in connection with which the patient was transferred to the intensive care unit and was on a ventilator for 24 hours. Thus, pulse oximetry gave a good measure of oxygenation, but did not provide direct information about progressive respiratory failure.

critically ill. In critically ill patients, the effectiveness of the method is low, since their tissue perfusion is poor and the pulse oximeter cannot determine the pulsating signal.

The presence of a pulse wave. If there is no visible pulse wave on the pulse oximeter, any saturation percentage numbers are of little value.

inaccuracy.

Bright external light, shivering, movement can create a pulse-like curve and pulseless saturation values.

Abnormal types of hemoglobin (eg, methemoglobin in prilocaine overdose) can give saturation values ​​as high as 85%.

Carboxyhemoglobin, which appears during carbon monoxide poisoning, can give a saturation value of about 100%. A pulse oximeter gives false readings in this pathology and should therefore not be used.

Dyes, including nail polish, can cause low saturation values.

Vasoconstriction and hypothermia cause a decrease in tissue perfusion and impair signal recording.

Tricuspid regurgitation causes venous pulsation and a pulse oximeter can detect venous oxygen saturation.

The saturation value below 70% is not accurate, because. no control values ​​to compare.

An arrhythmia can interfere with the pulse oximeter's perception of the pulse signal.

NB! Age, gender, anemia, jaundice, and dark skin have virtually no effect on the performance of the pulse oximeter.

? lagging monitor. This means that the partial pressure of oxygen in the blood can decrease much faster than saturation begins to decrease. If a healthy adult breathes 100% oxygen for a minute and then the ventilation stops for any reason, it may take several minutes before the saturation begins to decrease. A pulse oximeter under these conditions will warn of a potentially fatal complication only a few minutes after it has happened. Therefore, the pulse oximeter is called "sentinel, standing on the edge of the abyss of desaturation." The explanation for this fact is in the sigmoid shape of the oxyhemoglobin dissociation curve (Fig. 1).

reaction delay due to the fact that the signal is averaged. This means that there is a delay of 5-20 seconds between the actual oxygen saturation starting to drop and the values ​​on the pulse oximeter display changing.

Patient safety. There are one or two reports of burns and overpressure injury when using pulse oximeters. This is because early models used a heater in the transducers to improve local tissue perfusion. The sensor must be of the correct size and must not exert excessive pressure. Now there are sensors for pediatrics.

It is especially necessary to dwell on the correct position of the sensor. It is necessary that both parts of the sensor are symmetrical, otherwise the path between the photodetector and the LEDs will be unequal and one of the wavelengths will be "overloaded". Changing the position of the sensor often results in a sudden "improvement" in saturation. This effect may be due to unstable blood flow through pulsating dermal venules. Please note that the waveform in this case may be normal, because. the measurement is carried out only at one of the wavelengths.

Alternatives to pulse oximetry?

CO-oximetry is the gold standard and the classic method for calibrating a pulse oximeter. CO-oximeter calculates the actual concentration of hemoglobin, deoxyhemoglobin, carboxyhemoglobin, methemoglobin in the blood sample, and then calculates the actual oxygen saturation. CO-oximeters are more accurate than pulse oximeters (within 1%). However, they give saturation at a certain point (“snapshot”), are bulky, expensive, and require arterial blood sampling. They need constant maintenance.

Blood gas analysis - requires invasive sampling of the patient's arterial blood. It gives a "complete picture", including the partial pressure of oxygen and carbon dioxide in arterial blood, its pH, current bicarbonate and its deficiency, standardized bicarbonate concentration. Many gas analyzers calculate saturations that are less accurate than those calculated by pulse oximeters.

Finally

A pulse oximeter provides a non-invasive assessment of arterial hemoglobin oxygen saturation.

It is used in anesthesiology, awakening block, intensive care (including neonatal), during patient transportation.

Two principles are used:

Separate absorption of light by hemoglobin and oxyhemoglobin;

Extraction of the pulsating component from the signal.

Does not give direct indications for ventilation of the patient, only for his oxygenation.

Delay Monitor - There is a delay between the onset of potential hypoxia and the response of the pulse oximeter.

Inaccuracy with strong external light, shivering, vasoconstriction, abnormal hemoglobin, changes in pulse and rhythm.

In newer microprocessors, signal processing is improved.

CAPNOMETRY

Capnometry is the measurement and digital display of the concentration or partial pressure of carbon dioxide in inhaled and exhaled gas during a patient's respiratory cycle.

Capnography is a graphical display of the same indicators in the form of a curve. The two methods are not equivalent to each other, although if the capnographic curve is calibrated, then capnography includes capnometry.

Capnometry is rather limited in its capabilities and allows only to evaluate alveolar ventilation and detect the presence of reverse gas flow in the respiratory circuit (reuse of an already exhausted gas mixture). Capnography, in turn, not only has the above capabilities, but also allows you to evaluate and monitor the degree of tightness of the anesthesia system and its connection with the patient's airways, the operation of the ventilator, evaluate the functions cardiovascular system, as well as monitor some aspects of anesthesia, violations of which can lead to serious complications. Since disorders in these systems are diagnosed fairly quickly using capnography, the method itself serves as an early warning system in anesthesia. In the future, we will talk about the theoretical and practical aspects of capnography.

Physical basis of capnography

The capnograph consists of a gas sampling system for analysis and the anelizer itself. Two systems for gas sampling and two methods of its analysis are currently most widely used.

Gas intake : The most commonly used technique is to take gas directly from the patient's respiratory tract (usually, this is the junction of, for example, an endotracheal tube with a breathing circuit). A less common technique is when the sensor itself is located in close proximity to the respiratory tract, then as such there is no "intake" of gas.

Devices based on gas aspiration with its subsequent delivery to the analyzer, although they are the most common due to their greater flexibility and ease of use, still have some disadvantages. Water vapor can condense in the gas intake system, disrupting its permeability. When water vapor enters the analyzer, the measurement accuracy is significantly impaired. Since the analyzed gas is delivered to the analyzer with the expenditure of some time, there is some lag of the image on the screen from the actual events. For individually used analyzers, which are used most widely, this lag is measured in milliseconds and is of little practical importance. However, when using a centrally located instrument serving several operating rooms, this lag can be quite significant, which negates many of the advantages of the instrument. The rate of aspiration of gas from the respiratory tract also plays a role. In some models, it reaches 100 - 150 ml / min, which can affect, for example, the child's minute ventilation.

An alternative to suction systems are the so-called flow systems. In this case, the sensor is attached to the patient's airways using a special adapter and is located in close proximity to them. There is no need for aspiration of the gas mixture, since its analysis takes place right on the spot. The sensor is heated, which prevents the condensation of water vapor on it. However, these devices also have disadvantages. The adapter and sensor are quite bulky, adding 8 to 20 ml of dead space, which creates certain problems especially in pediatric anesthesiology. Both devices are located in close proximity to the patient's face, cases of injuries due to prolonged pressure of the sensor on the anatomical structures of the face have been described. It should be noted that the latest models of devices of this type are equipped with significantly lighter sensors, so it is possible that many of these shortcomings will be eliminated in the near future.

Gas mixture analysis methods : A fairly large number of gas mixture analysis methods have been developed to determine the concentration of carbon dioxide. Two of them are used in clinical practice: infrared spectrophotometry and mass spectrometry.

In systems using infrared spectrophotometry (the vast majority of them), the infrared beam is passed through the chamber with the analyzed gas.In this case, part of the radiation is absorbed by carbon dioxide molecules. The system compares the degree of absorption of infrared radiation in the measuring chamber with the control one. The result is displayed in graphical form.

Another technique for analyzing a gas mixture used in the clinic is mass spectrometry, when the analyzed gas mixture is ionized by bombardment with an electron beam. The charged particles thus obtained are passed through a magnetic field, where they are deflected by an angle proportional to their atomic mass. The deflection angle is the basis of the analysis. This technique allows for accurate and fast analysis of complex gas mixtures containing not only carbon dioxide, but also volatile anesthetics, and so on. The problem is that the mass spectrometer is very expensive, so not every clinic can afford it. Usually one device is used, connected to several operating rooms. In this case, the delay in displaying the results increases.

It should be noted that carbon dioxide is good soluble in blood and easily penetrates through biological membranes. This means that the value of the partial pressure of carbon dioxide at the end of expiration (EtCO2) in an ideal lung should correspond to the partial pressure of carbon dioxide in the arterial blood (PaCO2). In real life, this does not happen, there is always an arterial-alveolar gradient of CO2 partial pressure. In a healthy person, this gradient is small - about 1 - 3 mm Hg. The reason for the existence of the gradient is the uneven distribution of ventilation and perfusion in the lung, as well as the presence of a shunt. In lung diseases, such a gradient can reach a very significant value. Therefore, it is necessary to put an equal sign between EtCO2 and PaCO2 with great care.

Morphology of a normal capnogram : when graphically depicting the partial pressure of carbon dioxide in the patient's airways during inhalation and exhalation, a characteristic curve is obtained. Before proceeding to the description of its diagnostic capabilities, it is necessary to dwell in detail on the characteristics of a normal capnogram.

Rice. 1 Normal capnogram.

At the end of inhalation, the alveals contain gas, the partial pressure of carbon dioxide in which is in equilibrium with its partial pressure in the capillaries of the lungs. The gas contained in the more central sections of the respiratory tract contains less CO2, and the most centrally located sections do not contain it at all (concentration is 0). The volume of this CO2 free gas is the dead space volume.

With the beginning of exhalation, it is this gas, devoid of CO2, that enters the analyzer. On the curve, this is reflected in the form of a segment AB. As the exhalation continues, a gas containing CO2 in ever-increasing concentrations begins to flow into the analyzer. Therefore, starting from point B, there is a rise in the curve. Normally, this area (BC) is represented by an almost straight line, rising steeply. Near the very end of exhalation, when the air velocity decreases, the CO2 concentration approaches a value called the end-expiratory CO2 concentration (EtCO2). In this section of the curve (CD), the CO2 concentration changes little, reaching a plateau. The highest concentration is noted at point D, where it closely approaches the concentration of CO2 in the alveoli and can be used to approximate PaCO2.

With the beginning of inspiration, gas without CO2 enters the respiratory tract and its concentration in the analyzed gas drops sharply (segment DE). If there is no reuse of the exhaust gas mixture, then the CO2 concentration remains equal to or close to zero until the start of the next respiratory cycle. If such reuse occurs, then the concentration will be above zero and the curve will be higher and parallel to the isoline.

The capnogram can be recorded in two speeds - normal, as in Figure 1, or slow. When using the last detail of each breath, the general trend of CO2 change is more visible.

The capnogram contains information that allows you to judge the functions cardiovascular and respiratory systems, as well as the state of the gas mixture delivery system to the patient (respiratory circuit and ventilator). Below are typical examples of capnograms for various conditions.

Sudden fall EtCO 2 almost to zero

Such changes to a The diagram indicates a potentially dangerous situation (Fig. 2)

Fig.2 A sudden drop in EtCO2 to almost zero cansignify cessation of ventilation of the patient.

In this situation, the analyzer does not detect CO2 in the sample gas. Such a capnogram may occur with esophageal intubation, disconnection in the breathing circuit, ventilator stop, complete obstruction of the endotracheal tube. All these situations are accompanied by the complete disappearance of CO2 from the exhaled gas. In this situation, the capnogram does not make it possible to conduct a differential diagnosis, since it does not reflect any specific features characteristic of each situation. Only after auscultation of the chest, checking the color of the skin and mucous membranes and saturation should one think about other, less dangerous disorders, such as a breakdown of the analyzer or a violation of the patency of the gas sampling tube. If the disappearance of EtCO2 on the capnogram coincides with the movement of the patient's head, then in the first place, accidental extubation or disconnection of the breathing circuit should be ruled out.

Since one of the functions of ventilation is the removal of CO2 from the body, capnography is currently the only effective monitor to establish the presence of ventilation and gas exchange.

All of the above potentially fatal complications can happen at any time; they are easily diagnosed with capnography, highlighting the importance of this type of monitoring.

The fall EtCO 2 to low but not zero values

The figure shows a typical picture of such changes in the capnogram.

Slowlynormal speed

Fig 3. Sudden drop of EtCO 2 to a low level, but not to zero. Occurs with incomplete sampling of the analyzed gas. Shouldthink of partial airway obstruction orviolation of the tightness of the system.

A capnogram violation of this kind is an indication that for some reason the gas does not reach the analyzer during the entire exhalation. Exhaled gas can leak into the atmosphere through, for example, a poorly inflated cuff of the endotracheal tube or a poorly fitting mask. In this case, it is useful to check the pressure in the breathing circuit. If the pressure remains low during ventilation, there is probably a leak somewhere in the breathing circuit. Partial disconnection is also possible, when part of the tidal volume is still delivered to the patient.

If the pressure in the circuit is high, then partial obstruction of the breathing tube is most likely, which reduces the tidal volume delivered to the lungs.

Exponential decline EtCO 2

An exponential decrease in EtCO2 over a period of time, such as 10 to 15 respiratory cycles, indicates a potentially dangerous impairment of the cardiovascular or respiratory system. Violations of this kind must be corrected immediately to avoid serious complications.

Slowlynormal speed

Fig.4 An exponential decrease in EtCO 2 is observed during suddenPerfusion disorders of the lungs, such as when stopping hearts.

The physiological basis for the changes shown in Fig. 4 is a sudden significant increase in dead space ventilation, which leads to a sharp increase in the CO2 partial pressure gradient. disturbances leading to these types of capnogram disorders include, for example, severe hypotension (massive blood loss), circulatory arrest with ongoing mechanical ventilation, pulmonary embolism.

These violations are catastrophic in nature and, accordingly, rapid diagnosis of the incident is important. Auscultation (required to determine heart sounds), ECG, blood pressure measurement, pulse oximetry - these are the immediate diagnostic measures. If heart sounds are present, but blood pressure is low, it is necessary to check for obvious or hidden blood loss. A less obvious cause of hypotension is compression of the inferior vena cava by a retractor or other surgical instrument.

If heart sounds are auscultated, compression of the inferior vena cava and blood loss are ruled out as the cause of hypotension, pulmonary embolism should also be ruled out.

Only after these complications are excluded and the patient's condition is stable, one should think about other, more harmless reasons for changing the capnogram. The most common of these causes is an occasional unnoticed increase in ventilation.

Permanently low value EtCO 2 no pronounced plateau

Sometimes the capnogram presents the picture presented in Fig. 5 without any violations of the respiratory circuit or the patient's condition.

Slowlynormal speed

Fig.5 Constantly low value of EtCO 2 without a pronounced plateaumost often indicates a violation of gas intake for analysis.

In this case, EtCO 2 on the capnogram, of course, does not correspond to alveolar PACO 2 . The absence of a normal alveolar plateau means that either there is no complete exhalation before the next inspiration, or the exhaled gas is diluted with non-CO2 gas due to low tidal volume, too high gas sampling rate for analysis, or too high gas flow in the breathing circuit. There are several techniques for the differential diagnosis of these disorders.

Incomplete exhalation may be suspected if there are auscultatory signs of bronchoconstriction or accumulation of secretions in the bronchial tree. In this case, simple aspiration of the secretion can restore full exhalation, eliminating the obstruction. Treatment of bronchospasm is carried out according to the usual methods.

Partial bending of the endotracheal tube, overinflation of its cuff can reduce the lumen of the tube so much that a significant obstruction to inhalation appears with a decrease in its volume. Unsuccessful attempts at aspiration through the lumen of the tube confirm this diagnosis.

In the absence of evidence of partial airway obstruction, another explanation should be sought. In young children with small tidal volumes, gas intake for analysis may exceed end-tidal gas flow. In this case, the sample gas is diluted with fresh gas from the breathing circuit. Reducing the gas flow in the circuit or moving the gas sampling point closer to the endotracheal tube restores the capnogram plateau and raises EtCO 2 to a normal level. In newborns, it is often simply impossible to carry out these techniques, then the anesthesiologist must come to terms with the error of the capnogram.

Permanently low value EtCO 2 with a pronounced plateau

In some situations, the capnogram will reflect a constantly low value of EtCO2 with a pronounced plateau, accompanied by an increase in the arterial-alveolar gradient of CO 2 partial pressure (Fig. 6).

Slowlynormal speed

Fig.6 Constantly low value of EtCO2 with pronouncedalleolar plateau may be a sign of hyperventilationor increased dead space. Comparison of EtCO 2 andPaCO 2 makes it possible to distinguish between these two states.

It may seem that this is the result of a hardware error, which is quite possible, especially if calibration and service have been carried out for a long time. You can check the operation of the apparatus by determining your own EtCO 2 . If the device is working normally, then this shape of the curve is explained by the presence of a large physiological dead space in the patient. In adults, the cause is chronic obstructive pulmonary disease, in children - bronchopulmonary dysplasia. In addition, an increase in dead space may result from mild hypoperfusion of the pulmonary artery due to hypotension. In this case, correcting the hypotension restores a normal capnogram.

Constant decline EtCO 2

When the capnogram retains its normal shape, but there is a constant decrease in EtCO 2 (Fig. 7), several explanations are possible.

Slowlynormal speed

Rice. 7 A gradual decrease in EtCO2 indicates eithera decrease in CO 2 production, or a decrease in pulmonary perfusion.

These causes include a decrease in body temperature, which is usually seen with long-term surgery. This is accompanied by a decrease in metabolism and CO2 production. If at the same time the IVL parameters remain unchanged, then a gradual decrease in EtCO2 is observed. this decrease is better seen at low capnogram recording rates.

A more serious cause of this type of capnogram abnormality is a gradual decrease in systemic perfusion associated with blood loss, depression cardiovascular system or a combination of the two. With a decrease in systemic perfusion, pulmonary perfusion also decreases, which means that dead space increases, which is accompanied by the above-mentioned consequences. Correcting the hypoperfusion resolves the problem.

More common is the usual hyperventilation, accompanied by a gradual "washout" of CO 2 from the body with a characteristic picture on the but nogram.

gradual increase EtCO 2

A gradual increase in EtCO 2 with the preservation of the normal structure of the capnogram (Fig. 8) may be associated with violations of the tightness of the respiratory circuit, followed by hypoventilation.

Slowlynormal speed

Fig. 8 An increase in EtCO 2 is associated with hypoventilation, an increaseproduction of CO 2 or absorption of exogenous CO 2 (laparoscopy).

This also includes factors such as partial airway obstruction, fever (especially with malignant hyperthermia), CO 2 absorption during laparoscopy.

A small gas leak in the ventilator system, leading to a decrease in minute ventilation but maintaining a more or less adequate tidal volume, will be represented on a capnogram by a gradual increase in EtCO 2 due to hypoventilation. Re-sealing resolves the issue.

Partial airway obstruction sufficient to reduce effective ventilation but not impair exhalation produces a similar pattern on a capnogram.

An increase in body temperature due to too vigorous warming or the development of sepsis leads to an increase in CO 2 production, and, accordingly, an increase in EtCO 2 (subject to unchanged ventilation). With a very rapid rise in EtCO 2, one should keep in mind the possibility of developing a syndrome of malignant hyperthermia.

The absorption of CO 2 from exogenous sources, such as from the abdominal cavity during laparoscopy, leads to a situation similar to the increase in CO 2 production. This effect is usually obvious and immediately follows the onset of CO 2 insufflation into the abdominal cavity.

sudden rise EtCO 2

A sudden short-term increase in EtCO 2 (Fig. 9) can be caused by various factors that increase the delivery of CO 2 to the lungs.

Slowlynormal speed

Fig. 9 A sudden but short-term increase in EtCO 2 meansincreased delivery of CO 2 to the lungs.

The most common explanation for this change in capnogram is intravenous infusion of sodium bicarbonate with a corresponding increase in pulmonary CO2 excretion. This also includes the removal of the tourniquet from the limb, which opens the access of blood saturated with CO 2 to the systemic circulation. The rise of EtCO 2 after infusion of sodium bicarbonate is usually very short-lived, while a similar effect after the removal of the tourniquet lasts a longer time. None of the above events pose a serious threat or indicate any significant complications.

Sudden rise in contour

A sudden rise in the isoline on the capnogram leads to an increase in EtCO2 (Fig. 10) and indicates contamination of the measuring chamber of the device (saliva, mucus, and so on). All that is needed in this case is cleaning the camera.

Slowlynormal speed

Fig. 10 A sudden rise in the isoline on a capnogram is usuallyindicates contamination of the measuring chamber.

Gradual Level Up EtCO 2 and rise of the isoline

This type of change in the capnogram (Fig. 11) indicates the reuse of an already exhausted gas mixture containing CO 2 .

Slowlynormal speed

Fig.11 Gradual increase in EtCO 2 along with the levelisolines suggest reuserespiratory mixture.

The value of EtCO 2 usually increases until a new equilibrium is established between alveolar gas and arterial blood gases.

Although this phenomenon occurs quite often with different breathing systems, the occurrence of it when using a closed breathing circuit with an absorber during ventilation is a sign of serious violations in the circuit. The most common valve sticking occurs, which turns unidirectional gas flow into a pendulum. Another common cause of this capnogram disorder is depletion of the absorber capacity.

Incomplete neuromuscular block

Figure 12 shows a typical capnogram in an incomplete neuromuscular block, when diaphragmatic contractions appear and gas containing CO 2 enters the analyzer.

Slowlynormal speed

Fig.12 Such a capnogram indicates an incompleteneuromuscular block.

Since the diaphragm is more resistant to the action of muscle relaxants, its function is restored before the function of skeletal muscles. The capnogram in this case is a convenient diagnostic tool that allows you to roughly determine the degree of neuromuscular block during anesthesia.

Cardiogenic oscillations

This type of capnogram change is shown in Figure 13. it is caused by changes in intrathoracic volume according to stroke volume.

Slowlynormal speed

Fig.13. Cardiogenic oscillations look like teeth in the expiratory phase.

Usually, cardiogenic oscillations are observed with a relatively small tidal volume in combination with a low respiratory rate. Oscillations occur at the end of the respiratory phase of the capnogram during expiration, as the change in heart volume causes a small amount of gas to be “exhaled” with each heartbeat. This type of capinogram is a variant of the norm.

As can be seen from the above review, the capnogram serves as a valuable diagnostic tool, allowing not only to monitor the functions of the respiratory system, but also to diagnose disorders. cardiovascular systems. In addition, the capnogram allows you to detect violations in the anesthetic equipment at an early stage, thereby preventing the possibility of serious complications during anesthesia. Such qualities have made capnography an absolutely essential part of monitoring in modern anesthesiology, to the extent that a number of authors consider capnography more necessary than pulse oximetry.

The physiological rationale for the practical use of these tests are systemic (reflex) and local vascular reactions that occur in response to a change in the chemical (mainly gas) composition of the blood due to forced breathing or changes in the oxygen and/or carbon dioxide content in the inhaled air. Changes in blood chemistry cause irritation of the chemoreceptor
ditch of the aortic arch and carotid sinus zone with subsequent reflex changes in the frequency and depth of breathing, heart rate, blood pressure, peripheral vascular resistance and cardiac output. In the future, in response to changes in the gas composition of the blood, local vascular reactions develop.
One of the most important factors in the regulation of vascular tone is the level of oxygen content. Thus, an increase in oxygen tension in the blood causes contraction of arterioles and precapillary sphincters and restriction of blood flow, sometimes up to its complete cessation, which prevents tissue hyperoxia.
The lack of oxygen causes a decrease in vascular tone and an increase in blood flow, which is aimed at eliminating tissue hypoxia. This effect is significantly different in different organs: it is most pronounced in the heart and brain. It is assumed that adenosine (especially in the coronary bed), as well as carbon dioxide or hydrogen ions, can serve as a metabolic mediator of the hypoxic stimulus. The direct effect of oxygen deficiency on smooth muscle cells can be carried out in three ways: by changing the properties of excitable membranes, by intervening directly in the reactions of the contractile apparatus, and by influencing the content of energy substrates in the cell.
Carbon dioxide (CO2) has a pronounced vasomotor effect, an increase in which in most organs and tissues causes arterial vasodilation, and a decrease causes vasoconstriction. In some organs, this effect is due to a direct effect on the vascular wall, in others (the brain) it is mediated by a change in the concentration of hydrogen ions. In different organs, the vasomotor effect of CO2 differs significantly. It is less pronounced in the myocardium, but CO2 has a sharp effect on brain vessels: cerebral blood flow changes by 6% with a change in CO2 tension in the blood for every mmHg. from the normal level.
With severe voluntary hyperventilation, a decrease in the level of CO2 in the blood leads to such a pronounced cerebral vasoconstriction that cerebral blood flow can be halved, resulting in loss of consciousness.
The hyperventilation test is based on hypocapnia, hypersympathicotonia, respiratory alkalosis with a change in the concentration of potassium, sodium, magnesium ions, a decrease in the hydrogen content and an increase in the calcium content in the smooth muscle cells of the coronary arteries, which causes an increase in their tone and can provoke coronary spasm.
The indication for the test is the suspicion of spontaneous angina pectoris.
Methodology. The test is performed on a drug-free background early
in the morning, on an empty stomach, in the position of the patient lying down. The subject performs intense and deep breathing movements at a frequency of 30 breaths per minute for 5 minutes until a feeling of dizziness appears. Before the test, during the study and within 15 minutes after it (the possibility of delayed reactions), an ECG is recorded in 12 leads and blood pressure is recorded every 2 minutes.
The sample is considered positive when an ST segment shift of the “ischemic” type appears on the ECG.
In healthy people, hemodynamic changes during hyperventilation are an increase in heart rate, cardiac output, a decrease in peripheral vascular resistance, and multidirectional changes in blood pressure. It is believed that alkalosis and hypocapnia play an important role in the increase in heart rate and cardiac output. The decrease in TPVR during forced breathing depends on the vasodilating effect of hypocapnia and on the ratio of constrictor and dilating adrenergic effects realized through a- and P2-adrenergic receptors, respectively. Moreover, the severity of these hemodynamic reactions was more pronounced in young men.
In patients with IHD, hyperventilation contributes to a decrease in coronary blood flow due to vasoconstriction and an increase in the affinity of oxygen for hemoglobin. In this regard, the test can cause an attack of spontaneous angina pectoris in patients with severe atherosclerotic stenosis of the coronary arteries. In the detection of coronary artery disease, the sensitivity of the test with hyperventilation is 55-95%, and according to this indicator, it can be considered an alternative method in relation to the test with ergometrine when examining patients with a cardio-pain syndrome resembling spontaneous angina pectoris.
Hypoxemic (hypoxic) tests simulate situations in which the requirement for myocardial blood flow increases without increasing the work of the heart, and myocardial ischemia occurs with a sufficient volume of coronary blood flow. This phenomenon is observed in cases where the extraction of oxygen from the blood reaches the limit, for example, when the oxygen content in the arterial blood decreases. It is possible to simulate changes in the blood gas composition in humans in laboratory conditions using the so-called hypoxemic tests. These tests are based on the artificial reduction of the partial fraction of oxygen in the inhaled air. Oxygen deficiency in the presence of coronary pathology contributes to the development of myocardial ischemia and is accompanied by hemodynamic and local vascular reactions, and an increase in heart rate occurs in parallel with a decrease in oxygenation.
Indications. These tests can be used to assess the functional capacity of the coronary vessels, the state of coronary blood flow, and to detect latent coronary insufficiency. However, here
it is necessary to recognize the validity of the opinion of D.M. Aronov that at present, due to the advent of more informative methods, hypoxemic tests have lost their significance in the detection of coronary artery disease.
Contraindications. Hypoxemic tests are unsafe and contraindicated in patients with a recent myocardial infarction, with congenital and acquired heart defects, pregnant women, suffering from severe emphysema, or severe anemia.
Methodology. There are many ways to artificially create a hypoxic (hypoxemic) state, but their fundamental difference lies only in the content of CO2, so the samples can be divided into two options: 1) a sample with dosed normocapnic hypoxia; 2) samples with dosed hypercapnic hypoxia. When carrying out these tests, it is necessary to have an oximeter or oxyhemograph to record the degree of decrease in arterial oxygen saturation. In addition, monitor control of the ECG (12 leads) and blood pressure is carried out.

1. Breathing with a mixture with a reduced oxygen content. According to the method developed by R. Levy, the patient is allowed to breathe with a mixture of oxygen and nitrogen (10% oxygen and 90% nitrogen), while CO2 is removed from the exhaled air by a special absorber. BP and ECG parameters are recorded at 2-minute intervals for 20 minutes. At the end of the test, the patient is inhaled pure oxygen. If during the study there is pain in the region of the heart, the test is stopped.
2. To conduct a hypoxic test, a serial hypoxicator GP10-04 manufactured by Hypoxia Medical (Russia-Switzerland) can be used, which makes it possible to obtain respiratory gas mixtures with a given oxygen content. The device is equipped with a monitoring system for assessing hemoglobin saturation with oxygen. During this test, in our studies, the oxygen content in the inhaled air was lowered by 1% every 5 min, reaching a 10% concentration, which was maintained for 3 min, after which the test was stopped.
3. Achieving hypoxemia can be obtained by reducing the partial pressure of oxygen in the pressure chamber with a gradual decrease in atmospheric pressure, corresponding to a decrease in oxygen in the inhaled air. Controlled reduction of oxygen tension in arterial blood can reach the level of 65%.

1. Return breathing method. To conduct this study, we developed a closed circuit with a volume of 75 liters, in which the patient, reservoir and gas spiroanalyzer are connected in series using a system of hoses and valves. To calculate the volume of the tank, the formula was used:

During the test, the partial pressure of oxygen in the alveolar air, pulmonary ventilation, central hemodynamics, and ECG were monitored in the monitor mode. In the initial state and at the peak of the sample, samples of arterialized capillary blood were taken, in which, using the Astrup micromethod (analyzer BMS-3, Denmark), the tension of oxygen (pO2) and carbon dioxide (pCO2) of arterialized capillary blood was determined.
The test was stopped when the oxygen content in the inhaled air decreased to 14%, the minute respiratory volume reached 40-45% of its proper maximum value, and, in isolated cases, when the subject refused to perform the test. It should be noted that when using this test in 65 patients with coronary artery disease and 25 healthy individuals, in no case was an attack of angina pectoris or ECG changes of the “ischemic” type recorded.

1. Breathing through extra dead space. It is known that in humans the normal volume of dead space (nasopharynx, larynx, trachea, bronchi and bronchioles) is 130-160 ml. An artificial increase in the volume of dead space makes it difficult to aerate the alveoli, while in the inhaled and alveolar air, the partial pressure of CO2 increases, and the partial pressure of oxygen falls. In our study, to conduct a hypercapnic-hypoxic test, additional dead space was created by breathing with a mouthpiece through an elastic horizontally located tube (hose from a gas spiroanalyzer) with a diameter of 30 mm and a length of 145 cm (volume about 1000 ml). The duration of the test was 3 min, instrumental control methods and test termination criteria were the same as in the test with rebreathing.
2. CO2 inhalation can be used as a stress test to assess vascular reactivity. In our study, a gas mixture with a 7% CO2 content was dosed according to the level of the float in the rotameter of the domestic anesthesia machine RO-6R. The test was carried out in the horizontal position of the subject. Inhalation of atmospheric air (containing 20% ​​oxygen) with the addition of 7% CO2 was carried out in a constant mode using a mask. The duration of the test was 3 min, the control methods and evaluation criteria were similar to those described above. It should be noted a rather pronounced reflex hyperventilation, which developed on the 1-2nd minute from the start of the test. Before the study and after 3 minutes, samples of arterialized capillary blood were taken from the finger.