How to determine the stroke volume of blood. Minute volume of blood circulation. How to determine indicators of systolic function of the heart

Stroke and minute volume of the heart / blood: the essence, what they depend on, calculation

The heart is one of the main "workers" of our body. Not stopping for a minute during life, it pumps a huge amount of blood, providing nutrition to all organs and tissues of the body. The most important characteristics of the efficiency of blood flow are the minute and stroke volume of the heart, the values of which are determined by many factors both from the side of the heart itself and from the systems that regulate its work.

Minute blood volume (MBV) is a value that characterizes the amount of blood that the myocardium sends to the circulatory system within a minute. It is measured in liters per minute and equals approximately 4-6 liters at rest when horizontal position body. This means that all the blood contained in the vessels of the body, the heart is able to pump in a minute.

Stroke volume of the heart

Stroke volume (SV) is the volume of blood that the heart pushes into the vessels in one contraction. At rest, in an average person, it is about 50-70 ml. This indicator is directly related to the state of the heart muscle and its ability to contract with sufficient force. An increase in stroke volume occurs with an increase in pulse (up to 90 ml or more). In athletes, this figure is much higher than in untrained individuals, even if the heart rate is approximately the same.

The volume of blood that the myocardium can eject into the great vessels is not constant. It is determined by the requests of the authorities in specific conditions. So, during intense physical activity, excitement, in a state of sleep, the organs consume different amount blood. The effects on myocardial contractility from the nervous and endocrine systems also differ.

With an increase in the frequency of contractions of the heart, the force with which the myocardium pushes out blood increases, and the volume of fluid entering the vessels increases due to the significant functional reserve of the organ. The reserve capacity of the heart is quite high: in untrained people during exercise cardiac output per minute reaches 400%, that is, the minute volume of blood ejected by the heart increases up to 4 times, for athletes this figure is even higher, their minute volume increases by 5-7 times and reaches 40 liters per minute.

Physiological features of heart contractions

The volume of blood pumped by the heart per minute (MOC) is determined by several components:

stroke volume of the heart;
The frequency of contractions per minute;
The volume of blood returned through the veins (venous return).

By the end of the period of relaxation of the myocardium (diastole), a certain amount of fluid accumulates in the cavities of the heart, but not all of it then enters the systemic circulation. Only a part of it goes into the vessels and makes up the stroke volume, which in quantity does not exceed half of all the blood that entered the heart chamber during its relaxation.

The blood remaining in the cavity of the heart (about half or 2/3) is the reserve volume required by the organ in cases where blood needs increase (during physical exertion, emotional stress) and also not a large number of residual blood. Due to the reserve volume, with an increase in the heart rate, the IOC also increases.

The blood present in the heart after systole (contraction) is called the end-diastolic volume, but even it cannot be completely evacuated. After the release of the reserve volume of blood in the cavity of the heart, there will still be some amount of fluid that will not be ejected from there even with the maximum work of the myocardium - the residual volume of the heart.

cardiac cycle; stroke, end systolic and end diastolic volumes of the heart

Thus, during contraction, the heart does not throw all the blood into the systemic circulation. First, the stroke volume is pushed out of it, if necessary, a reserve volume, and after that the residual volume remains. The ratio of these indicators indicates the intensity of the work of the heart muscle, the strength of contractions and the efficiency of systole, as well as the ability of the heart to provide hemodynamics in specific conditions.

IOC and sport

The main reason for the change in the minute volume of blood circulation in healthy body consider physical activity. It could be classes in gym, jogging, fast walk etc. Another condition for the physiological increase in minute volume can be considered excitement and emotions, especially in those who acutely perceive any life situation, reacting to it with an increase in heart rate.

When performing intensive sports exercises stroke volume increases, but not to infinity. When the load has reached approximately half of the maximum possible, the stroke volume stabilizes and takes on a relatively constant value. Such a change in the output of the heart is associated with the fact that when the pulse accelerates, the diastole is shortened, which means that the chambers of the heart will not be filled with the maximum possible amount of blood, so the stroke volume indicator will sooner or later stop increasing.

On the other hand, working muscles consume a large amount of blood that does not return to the heart during sports activities, thus reducing venous return and the degree of filling of the chambers of the heart with blood.

The main mechanism that determines the rate of stroke volume is the distensibility of the ventricular myocardium.. The more the ventricle is stretched, the more blood will enter him and the higher will be the force with which he will send it to the main vessels. With an increase in the intensity of the load, the level of stroke volume, to a greater extent than extensibility, is affected by the contractility of cardiomyocytes - the second mechanism that regulates the value of stroke volume. Without good contractility, even the most filled ventricle will not be able to increase its stroke volume.

It should be noted that in myocardial pathology, the mechanisms regulating the IOC acquire a slightly different meaning. For example, hyperextension of the heart walls in conditions of decompensated heart failure, myocardial dystrophy, myocarditis and other diseases will not cause an increase in stroke and minute volumes, since the myocardium does not have sufficient strength for this, as a result, systolic function will decrease.
During the period sports training both shock and minute volumes increase, but only the influence sympathetic innervation not enough for this. Increasing the IOC helps in parallel increasing venous return due to active and deep breaths, pumping action of contracting skeletal muscles, increasing the tone of the veins and blood flow through the arteries of the muscles.
Increased blood volume with physical work helps to provide nutrition to the myocardium that is in great need of it, to deliver blood to working muscles, and also skin for proper thermoregulation.

As the load increases, blood delivery to the coronary arteries Therefore, before starting endurance training, you should warm up and warm up the muscles. In healthy people, neglect of this moment can go unnoticed, and in the pathology of the heart muscle, ischemic changes are possible, accompanied by pain in the heart and characteristic electrocardiographic signs (depression of the ST segment).

How to determine the indicators of systolic function of the heart?

Values systolic function myocardial is calculated according to various formulas, with the help of which a specialist judges the work of the heart, taking into account the frequency of its contractions.

ejection fraction of the heart

The systolic volume of the heart divided by the body surface area (m²) will be cardiac index. The surface area of the body is calculated using special tables or a formula. In addition to cardiac index, cardiac output and stroke volume, the most important characteristic myocardial work is considered, which shows what percentage of end-diastolic blood leaves the heart during systole. It is calculated by dividing the stroke volume by the end-diastolic volume and multiplying by 100%.

When calculating these characteristics, the doctor must take into account all the factors that can change each indicator.

The end-diastolic volume and filling of the heart with blood is influenced by:

The amount of circulating blood;

The amount of blood entering right atrium from the veins of the large circle;

The frequency of contractions of the atria and ventricles and the synchronism of their work;

The duration of the period of relaxation of the myocardium (diastole).

An increase in minute and stroke volume is facilitated by:

An increase in the amount of circulating blood with water and sodium retention (not provoked by cardiac pathology);

The horizontal position of the body, when the venous return to the right parts of the heart naturally increases;

Psycho-emotional tension, stress, strong excitement (due to increased heart rate and increased contractility of venous vessels).

A decrease in cardiac output accompanies:

Blood loss, shocks, dehydration;

Vertical position of the body;

The increase in pressure in chest cavity(obstructive pulmonary disease, pneumothorax, severe dry cough) or heart sac (pericarditis, fluid accumulation);

Fainting, collapse, taking drugs that cause sharp drop pressure and varicose veins;

Some types, when the chambers of the heart do not contract synchronously and are not sufficiently filled with blood in diastole (atrial fibrillation), severe tachycardia, when the heart does not have time to fill with the necessary volume of blood;

Myocardial pathology (, heart attack, inflammatory changes, and etc.).

The stroke volume of the left ventricle is influenced by the tone of the autonomic nervous system, pulse rate, condition of the heart muscle. So frequent pathological conditions, as myocardial infarction, cardiosclerosis, dilatation of the heart muscle in decompensated organ failure contribute to a decrease in the contractility of cardiomyocytes, so cardiac output will naturally decrease.

Reception medicines also determines the performance of the heart. Epinephrine, norepinephrine, increase myocardial contractility and increase the IOC, while, barbiturates, some reduce cardiac output.

Thus, the parameters of the minute and SV are influenced by many factors, ranging from the position of the body in space, physical activity, emotions and ending with the most various pathologies heart and blood vessels. When assessing systolic function, the doctor relies on general state, age, sex of the subject, the presence or absence of structural changes in the myocardium, arrhythmias, etc. Only A complex approach can help to correctly assess the efficiency of the heart and create conditions under which it will contract in the optimal mode.

Every minute a man's heart pumps a certain amount of blood. This indicator is different for everyone, it can vary according to age, physical activity and health status. The minute volume of blood is important for determining the efficiency of the functioning of the heart.
The amount of blood that the human heart pumps in 60 seconds is called the minute volume of blood (MBV). The stroke (systolic) volume of blood is the amount of blood ejected into the arteries in one heart contraction(systole). The systolic volume (SV) can be calculated by dividing the IOC by the heart rate. Accordingly, with an increase in SOC, the IOC also increases. The values of systolic and minute blood volumes are used by doctors to assess the pumping ability of the heart muscle.

IOC value depends not only on stroke volume and heart rate but also from venous return (the amount of blood returned to the heart through the veins). Not all blood is expelled in one systole. Some of the fluid remains in the heart as a reserve (reserve volume). It is used for increased physical exertion, emotional stress. But even after the release of reserves, a certain amount of liquid remains, which is not thrown out under any circumstances.

This is called residual myocardial volume.

Norm of indicators

Normal in the absence of IOC voltage equal to 4.5-5 liters. That is, healthy heart pumps all the blood in 60 seconds. The systolic volume at rest, for example, with a pulse of up to 75 beats, does not exceed 70 ml.

With physical activity, the heart rate rises, and therefore the indicators also increase. This comes from reserves. The body includes a system of self-regulation. In untrained people, the minute blood output increases 4-5 times, that is, it is 20-25 liters. In professional athletes, the value changes by 600-700%, their myocardium pumps up to 40 liters per minute.
An untrained body cannot withstand maximum stress for a long time, therefore it responds with a decrease in COC.

Minute volume, stroke volume, pulse rate are interconnected, they depend on many factors:

The weight of a person. With obesity, the heart has to work with a vengeance to supply oxygen to all cells.

The ratio of body weight and myocardial weight. In a person weighing 60 kg, the mass of the heart muscle is approximately 110 ml.

State venous system. Venous return should be equal to the IOC. If the valves in the veins do not work well, then not all the fluid returns back to the myocardium.

Age. In children, the IOC is almost twice as large as in adults. Happens with age natural aging myocardium, so the SOC and IOC are reduced.

Physical activity. Athletes have higher values.

Pregnancy. The mother's body works in an enhanced mode, the heart pumps much more blood per minute.

Bad habits. When smoking and drinking alcohol, the blood vessels narrow, so there is a decrease in the IOC, since the heart does not have time to pump the required volume of blood.

Deviation from the norm

Decline in IOC occurs in various cardiac pathologies:

Atherosclerosis.

Heart attack.

Mitral valve prolapse.

Blood loss.

Arrhythmia.

Reception of some medical preparations: barbiturates, antiarrhythmic drugs, lowering blood pressure.

In patients, the volume of circulating blood decreases, it does not enter the heart enough.

Developing low cardiac output syndrome. This is expressed in a decrease in blood pressure, a drop in heart rate, tachycardia, and pallor of the skin.

Cardiac output, or cardiac output, is the amount of blood that the heart pumps per minute (measured in liters per minute). It measures how efficiently the heart delivers oxygen and nutrients to the body and how well it functions compared to the rest of the cardiovascular system. To determine cardiac output, it is necessary to determine the stroke volume and heartbeat. This can only be done by a doctor using an echocardiogram.

Steps

Determination of heart rate

Take a stopwatch or watch. Heart rate is the number of heartbeats per unit of time. It is usually measured in one minute. This is very easy to do, but you will need a device that accurately counts seconds.
You can try to count the beats and seconds mentally, but this will be inaccurate, as you will be focused on the pulse, and not on the internal sense of time.

It's better to set a timer so that you can only concentrate on counting the hits. The timer is in your smartphone.

Find a pulse. Although there are many points on the body where you can feel the pulse, the easiest way to find it is on the inside of the wrist. Another place - on the side of the throat, where it is located jugular vein. When you feel the pulse and clearly feel its beats, put your index and middle fingers other hand.
The pulse is usually best felt with inside wrist, on a line mentally drawn from index finger across the wrist and about 5 cm above the first crease on it.

You may need to move your fingers back and forth a little to find where the pulse is heard most clearly.

You can lightly press your fingers on your wrist to feel for a pulse. However, if you have to push too hard, you have chosen the wrong place. Try moving your fingers to a different point.

Start counting the number of beats. When you find a pulse, turn on the stopwatch or look at the clock with a second hand, wait until it reaches 12 and start counting the beats. Count the number of beats in one minute (until the second hand returns to 12). This number is your heart rate.
If you find it difficult to count beats for a full minute, you can count 30 seconds (until the second hand is at 6), and then multiply the result by two.

You can also count the beats in 15 seconds and multiply by 4.

Stroke volume determination

Get an echocardiogram. Heart rate is simply the number of times the heart beats per minute, and stroke volume is the volume of blood pumped from the left ventricle of the heart with each beat. It is measured in milliliters, and it is much more difficult to determine it. For this, it is carried out special study called echocardiography (echo).

Calculate the area of the left ventricular outlet (LVOT). The left ventricular outlet is the area of the heart through which blood enters the arteries. To calculate stroke volume, you need to know the left ventricular outflow tract area (LVOT) and the integral of the left ventricular outflow tract flow velocity (LVOT).

Determine the integral of the blood flow velocity. The integral of blood flow velocity is the integral of the rate at which blood flows through a vessel or through a valve in certain time. To calculate VOLV IS, the specialist will measure the flow using Doppler echocardiography. To do this, he uses a special function of the echocardiograph.
To determine the IS VOLZH, calculate the area under the curve of the aorta on pulsed wave Doppler. The specialist can take multiple measurements to make a conclusion about the efficiency of your heart.

Calculate stroke volume. To determine stroke volume, subtract the volume of blood in the ventricle before the stroke (end diastolic volume, EDV) from the volume of blood in the ventricle at the end of the stroke (end systolic volume, ESV). Stroke volume \u003d BDO - KSO. As a rule, stroke volume is associated with the left ventricle, but it can also apply to the right. Usually the stroke volume of both ventricles is the same.

Determine cardiac output. Finally, to calculate cardiac output, multiply the heart rate by the stroke volume. This is a fairly simple calculation that will tell you how much blood your heart pumps in one minute. The formula is: Heart rate x Stroke volume = Cardiac output. For example, if the heart rate is 60 beats per minute and the stroke volume is 70 ml, you get:

Factors affecting cardiac output

Understand what heart rate means. You will better understand what cardiac output is if you know what influences it. The most immediate factor is the heart rate (pulse), that is, the number of heartbeats per minute. The faster the pulse, the more blood is pumped throughout the body. Normal frequency heart rate is 60-100 beats per minute. If the heart beats too slowly, it is called bradycardia, a condition in which the heart pumps too little blood into the circulation.

For some beginner runners, the question arises, “how healthy is it to run long and often in the upper heart rate zones?”. And here we again run into the issue of cardio fitness. vascular system, muscles and the new phrase "stroke volume of the heart" (SV). The stroke volume of the heart is the portion of blood ejected by the left ventricle in 1 contraction.

AT the first part of the article I showed. In second part consider the stroke volume of the heart, the work of the heart at an increased heart rate.

With each contraction of the heart in an adult (at rest), 50-70 ml of blood is ejected into the aorta and pulmonary trunk, 4-5 liters per minute. With a large physical stress minute volume can reach 30 - 40 liters. In other words, the athlete's heart is stretched to such a size that it can pump more than 200 ml of blood in one contraction. For example, the heart of a professional athlete when working for a minute at a pulse of 180 bpm. can pump 36 liters. blood. These are 4 buckets of 10 liters each!

For each person, VR is individual, depends on hereditary data and fitness. In women, for example, SV is 10-15% less than in men.

A person with an athletic heart (having a higher VR) has a higher endurance index, especially for prolonged physical exertion (marathon, cycling, long-distance swimming).

What effect does exercise have on the heart?

An increase in heart rate (HR)

Increased stroke volume (SV)

An increase in systolic pressure

Decreased diastolic pressure and peripheral vascular resistance

The respiratory rate increases

Increased coronary blood flow

There is a redistribution of blood (blood will be in the working muscle)

The effect of aerobic exercise (long-term)

Athletic heart (increase in size and strength of contraction)

Decreased heart rate

Increase in the number of capillaries in the muscles

Stroke volume during exercise.

The stroke volume of the heart increases with the growth of the pulse until and until the intensity of physical activity reaches the level of 40-60% of the maximum possible. After that, the UO is leveled. That is, when running at a pulse of 120-150 beats per minute, the heart is ergonomically stretched and contracted, optimally ensuring the exchange of oxygen and nutrients in the muscles, freeing itself from CO2 and enriching itself with O2 again. Therefore, in order to “stretch” the heart and increase VR, it is recommended to run for 2-3 hours a day, for 6 months!

Surely some noticed that you run and run for 20-30 minutes, the pulse is high, and after that from 150-155 bpm. it drops to 135 bpm. at the same intensity. This is an indicator that the heart has reached the norm of its MR, the vessels and capillaries of the body have started to work.

With prolonged physical activity of 40-60% of the maximum (or 120-150 bpm when running), the chamber of the left / right ventricle is stretched, as it enters maximum amount blood in this manner. If the chamber of the ventricle is stretched (diastole phase), then, accordingly, it should further contract as much as possible (systole phase) in order to expel blood.

The work of the heart with increased heart rate.

In the case when the load increases, when working in the 4th-5th pulse zone(PZ), then the heartbeat increases, the pulse too. The phase of systole and diastole (contraction and relaxation) becomes more frequent. Why can't we run on a heart rate of 170-180 bpm for as long as on a pulse of 150 bpm? The thing is the following...

On the increased heart rate the blood does not have time to be fully enriched with oxygen, and also the ventricular chamber does not have time to fully stretch, as on a pulse of 140 beats per minute, and also fully, to contract as much as possible to push out the blood. It turns out that the blood is not completely enriched and the heart also begins to “rush” and passes smaller portions of blood through the ventricle with rapid relaxation and rapid contraction.

SV with increased heart rate will decrease, oxygen exchange between muscle tissues(upper/ lower limbs), which will limit the performance of the work.

Accordingly, in this mode (anaerobic glycolysis), the athlete will not be able to show high results for a long time. With a decrease in nutrients and oxygen supplied to the muscles, as we know, the body in an anaerobic mode begins to use glucose, muscle glycogen, while releasing pyruvate, lactate, which enters the blood. Together with lactate, the amount of hydrogen ions (H+) increases. And now an excess of H + destroys protein and myofibrils. AT a small amount it contributes to an increase in strength, and in excess, with strong acidification, only harms the body. If there is a lot of H + and they are in the blood for a long time, then this also reduces the aerobic capacity of the athlete, endurance, as it destroys mitochondria.

But the good news is that with the help of competent interval training, tempo training, we can increase the buffering capacity of the body, increasing the VO2 max and pushing back the TAN.

Interval training, especially among professional athletes and even amateurs who work for the result, is associated with large intervals of 1000 m and above, and these workouts are very exhausting not only physical state but also the nervous system. If they are done often, then this can lead to overtraining, inflammation, disease, injury. In my opinion, depending on the period of preparation of the athlete and the level of the athlete, 1-2 diverse interval training sessions per week or even 1 time in 2 weeks is enough.

The more often the heart rate, the more the biochemistry shifts towards anaerobic metabolism, the less time we can perform this or that work. The higher the heart rate, the more oxygen and energy the muscles need to consume. As a result, the heart muscle will receive less nutrition, which will lead to ischemia (impaired cardiac circulation) of the heart.

In order to increase endurance, it is not enough just to increase the stroke volume of the heart (SV). The condition of the muscles, capillaryization and development also matter here. circulatory system. These qualities develop in the process of training.

Interval training is also different: short intense and long (not at full strength). The first can last 10-20 minutes, and the second 40-60 minutes or more. The more intense the interval, the higher the heart rate (pulse), the stronger the heart muscle pumps up, the elasticity decreases.

You need to understand that interval training at maximum heart rate is acceptable if you are a professional athlete and are preparing for competitions. Prolonged exercise in this mode is undesirable for health, as it leads to acidification of not only the muscles, but also the heart.

Exercising at too high a heart rate leads to hypertrophy of the heart muscle and a decrease in stroke volume, and as a result can lead to heart failure and even lethal outcome. Therefore, a competent preparation of a training plan and an understanding of the specifics of training exercises allows you to consistently and evenly develop body functions without harm to health.

What threatens the health of an athlete for a long run on high heart rate Or how does the body protect us from the sad consequences?

1) First, fatigue of the body appears, then the working muscles (arms, legs) become clogged, they become wadded.

2) Vomiting reflex, nausea, as a reaction to acidification of the body.

3) Shutdown of the central nervous system, loss of consciousness.

4) Cardiac arrest.

We are now smart and we will not bring ourselves to the state of the 4th point.

Throws a certain amount of blood into the vessels. In that main function of the heart. Therefore, one of the indicators functional state heart is the value of minute and shock (systolic) volumes. The study of the value of minute volume is of practical importance and is used in the physiology of sports, clinical medicine and professional hygiene.

The amount of blood ejected by the heart per minute is called minute volume of blood(IOC). The amount of blood pumped out by the heart in one beat is called stroke (systolic) blood volume(WOK).

The minute volume of blood in a person in a state of relative rest is 4.5-5 liters. It is the same for the right and left ventricles. Stroke volume can be easily calculated by dividing the IOC by the number of heartbeats.

Training is of great importance in changing the magnitude of minute and stroke volumes of blood. When performing the same work in a trained person, the value of systolic and minute volumes of the heart increases significantly with a slight increase in the number of heartbeats; in an untrained person, on the contrary, the heart rate increases significantly and the systolic blood volume hardly changes.

SVR increases with increased blood flow to the heart. As the systolic volume increases, so does the IOC.

Stroke volume of the heart

An important characteristic of the pumping function of the heart gives stroke volume, also called systolic volume.

Stroke volume(VV) - the amount of blood ejected by the ventricle of the heart in arterial system for one systole (sometimes the name is used systolic output).

Since the large and small are connected in series, in a stable hemodynamic regime, the stroke volumes of the left and right ventricles are usually equal. Only on a short time during the period abrupt change the work of the heart and hemodynamics between them there may be a slight difference. The value of the SV of an adult at rest is 55-90 ml, and during exercise it can increase up to 120 ml (for athletes up to 200 ml).

Starr formula (systolic volume):

CO \u003d 90.97 + 0.54. PD - 0.57. DD - 0.61. AT,

where CO is systolic volume, ml; PD — pulse pressure, mm Hg. Art.; DD — diastolic pressure, mm Hg. Art.; B - age, years.

Normal CO at rest is 70-80 ml, and during exercise - 140-170 ml.

End diastolic volume

End diastolic volume(EDV) is the amount of blood in the ventricle at the end of diastole (at rest, about 130-150 ml, but depending on gender, age, it can vary between 90-150 ml). It is formed by three volumes of blood: remaining in the ventricle after the previous systole, inflowing from the venous system during total diastole, and pumped into the ventricle during atrial systole.

Table. End-diastolic blood volume and its components

End systolic volume

End-systolic volume(KSO) is the amount of blood remaining in the ventricle immediately after. At rest, it is less than 50% of the end-diastolic volume, or 50-60 ml. Part of this blood volume is a reserve volume that can be expelled with an increase in the strength of heart contractions (for example, during exercise, an increase in the tone of the centers of the sympathetic nervous system, the action of adrenaline, thyroid hormones on the heart).

A number of quantitative indicators, currently measured by ultrasound or by probing the cavities of the heart, are used to assess the contractility of the heart muscle. These include indicators of the ejection fraction, the rate of blood ejection in the rapid ejection phase, the rate of pressure increase in the ventricle during the stress period (measured by ventricular probing) and a number of cardiac indices.

Ejection fraction(EF) - expressed as a percentage of the ratio of stroke volume to the end-diastolic volume of the ventricle. ejection fraction healthy person at rest is 50-75%, and during exercise it can reach 80%.

The rate of expulsion of blood measured by Doppler ultrasound of the heart.

Pressure increase rate in the cavities of the ventricles is considered one of the most reliable indicators of myocardial contractility. For the left ventricle, the value of this indicator is normally 2000-2500 mm Hg. st./s.

A decrease in ejection fraction below 50%, a decrease in the rate of blood expulsion, and a decrease in the rate of pressure increase indicate a decrease in myocardial contractility and the possibility of developing insufficiency in the pumping function of the heart.

Minute volume of blood flow

Minute volume of blood flow(MOC) - an indicator of the pumping function of the heart, equal to the volume of blood expelled by the ventricle into the vascular system in 1 minute (the name is also used minute burst).

IOC = UO. heart rate.

Since the SV and HR of the left and right ventricles are equal, their IOC is also the same. Thus, the same volume of blood flows through the small and large circles of blood circulation in the same period of time. In mowing, the IOC is 4-6 liters, with physical exertion it can reach 20-25 liters, and for athletes - 30 liters or more.
Methods for determining the minute volume of blood circulation
Direct Methods: catheterization of the heart cavities with the introduction of sensors - flowmeters.

Indirect Methods:

Fick method:

where IOC is the minute volume of blood circulation, ml/min; VO 2 - oxygen consumption in 1 min, ml/min; CaO 2 - oxygen content in 100 ml arterial blood; CvO 2 - oxygen content in 100 ml of venous blood

Dilution method of indicators:

where J is the amount of the administered substance, mg; C is the average concentration of the substance calculated from the dilution curve, mg/l; T-duration of the first wave of circulation, s

Ultrasonic flowmetry

Tetrapolar thoracic rheography

Cardiac index

Cardiac index(SI) - the ratio of the minute volume of blood flow to the body surface area (S):

SI = IOC / S(l / min / m 2).

where IOC is the minute volume of blood circulation, l/min; S - body surface area, m 2.

Normally, SI \u003d 3-4 l / min / m 2.

The work of the heart ensures the movement of blood through the system blood vessels. Even in living conditions without physical activity The heart pumps up to 10 tons of blood per day. The useful work of the heart is spent on creating blood pressure and giving it acceleration.

To give acceleration to portions of ejected blood, the ventricles spend about 1% of common work and energy costs of the heart. Therefore, this value can be neglected in calculations. Almost all the useful work of the heart is spent on creating pressure - the driving force of blood flow. Work (A) performed by the left ventricle of the heart during one cardiac cycle, is equal to the product of the mean pressure (P) in the aorta and the stroke volume (SV):

At rest, in one systole, the left ventricle performs work of about 1 N / m (1 N \u003d 0.1 kg), and the right ventricle is approximately 7 times less. This is due to the low resistance of the vessels of the pulmonary circulation, as a result of which the blood flow in the pulmonary vessels is provided at an average pressure of 13-15 mm Hg. Art., while in big circle circulatory mean pressure is 80-100 mm Hg. Art. Thus, the left ventricle needs to spend approximately 7 times great job than the right one. This leads to the development of more muscle mass left ventricle compared to the right.

Performing work requires energy costs. They go beyond providing useful work, but also to maintain basic life processes, ion transport, renewal cell structures, synthesis of organic substances. Coefficient useful action heart muscle is in the range of 15-40%.

The energy of ATP, necessary for the vital activity of the heart, is obtained mainly in the course of oxidative phosphorylation, carried out with the obligatory consumption of oxygen. At the same time, various substances can be oxidized in the mitochondria of cardiomyocytes: glucose, free fatty acid, amino acids, lactic acid, ketone bodies. In this regard, the myocardium (as opposed to nervous tissue, which uses glucose for energy) is an "omnivorous organ". To ensure energy needs the heart at rest in 1 min requires 24-30 ml of oxygen, which is about 10% of the total oxygen consumption by the adult body for the same time. Up to 80% of oxygen is extracted from the blood flowing through the capillaries of the heart. In other organs, this figure is much less. Oxygen delivery is the weakest link in the mechanisms that supply the heart with energy. This is due to the peculiarities of cardiac blood flow. Insufficiency of oxygen delivery to the myocardium, associated with impaired coronary blood flow, is the most common pathology leading to the development of myocardial infarction.

Ejection fraction

Ejection fraction = CO / EDV

where CO is systolic volume, ml; EDV — end diastolic volume, ml.

The ejection fraction at rest is 50-60%.

Blood flow rate

According to the laws of hydrodynamics, the amount of liquid (Q) flowing through any pipe is directly proportional to the pressure difference at the beginning (P 1) and at the end (P 2) of the pipe and inversely proportional to the resistance (R) to the fluid flow:

Q \u003d (P 1 -P 2) / R.

If we apply this equation to the vascular system, then it should be borne in mind that the pressure at the end of this system, i.e. at the confluence of the hollow veins in the heart, close to zero. In this case, the equation can be written as:

Q=P/R

where Q- the amount of blood expelled by the heart per minute; R- the value of the average pressure in the aorta; R is the value of vascular resistance.

It follows from this equation that P = Q*R, i.e. pressure (P) at the mouth of the aorta is directly proportional to the volume of blood ejected by the heart in the arteries per minute (Q), and the value of peripheral resistance (R). Aortic pressure (P) and minute volume (Q) can be measured directly. Knowing these values, calculate the peripheral resistance - the most important indicator condition of the vascular system.

The peripheral resistance of the vascular system is the sum of many individual resistances of each vessel. Any of these vessels can be likened to a tube, the resistance of which is determined by the Poiseuille formula:

where L- length of the tube; η is the viscosity of the liquid flowing in it; Π is the ratio of the circumference to the diameter; r is the tube radius.

The difference in blood pressure, which determines the speed of blood movement through the vessels, is large in humans. In an adult, the maximum pressure in the aorta is 150 mm Hg. Art., and in large arteries- 120-130 mm Hg. Art. In smaller arteries, blood encounters greater resistance and the pressure here drops significantly - up to 60-80 mm. rt st. The sharpest decrease in pressure is observed in arterioles and capillaries: in arterioles it is 20-40 mm Hg. Art., and in the capillaries - 15-25 mm Hg. Art. In the veins, the pressure decreases to 3-8 mm Hg. Art., in the hollow veins, the pressure is negative: -2-4 mm Hg. Art., i.e. at 2-4 mm Hg. Art. below atmospheric. This is due to a change in pressure in the chest cavity. During inhalation, when the pressure in the chest cavity decreases significantly, it decreases and blood pressure in hollow veins.

From the above data, it can be seen that blood pressure in different areas bloodstream is not the same, and it decreases from the arterial end of the vascular system to the venous. In large and medium arteries, it decreases slightly, by approximately 10%, and in arterioles and capillaries - by 85%. This indicates that 10% of the energy developed by the heart during contraction is spent on the movement of blood in large arteries, and 85% is spent on its movement through the arterioles and capillaries (Fig. 1).

Rice. 1. Change in pressure, resistance and lumen of blood vessels in different parts of the vascular system

The main resistance to blood flow occurs in the arterioles. The system of arteries and arterioles is called vessels of resistance or resistive vessels.

Arterioles are vessels of small diameter - 15-70 microns. Their wall contains a thick layer of circularly located smooth muscle cells, with the reduction of which the lumen of the vessel can significantly decrease. At the same time, the resistance of arterioles sharply increases, which makes it difficult for blood to flow out of the arteries, and the pressure in them rises.

A decrease in the tone of arterioles increases the outflow of blood from the arteries, which leads to a decrease in blood pressure(HELL). Among all parts of the vascular system, it is the arterioles that have the greatest resistance, so the change in their lumen is the main regulator of the level of total arterial pressure. Arterioles are the "faucets of the circulatory system". The opening of these "faucets" increases the outflow of blood into the capillaries of the corresponding area, improving local blood circulation, and the closure sharply worsens the blood circulation of this vascular zone.

Thus, arterioles play a dual role:

involved in maintaining necessary for the body level of general arterial pressure;

participate in the regulation of the magnitude of local blood flow through a particular organ or tissue.

The amount of organ blood flow corresponds to the organ's need for oxygen and nutrients, determined by the level of activity of the organ.

In a working organ, the tone of the arterioles decreases, which ensures an increase in blood flow. So that the total blood pressure does not decrease in other (non-functioning) organs, the tone of the arterioles increases. The total value of the total peripheral resistance and general level BP remains approximately constant, despite the continuous redistribution of blood between working and non-working organs.

Volumetric and linear velocity of blood movement

Volumetric speed blood flow is the amount of blood flowing per unit time through the sum of the cross sections of the vessels of a given section of the vascular bed. Through the aorta pulmonary arteries, vena cava and capillaries in one minute the same volume of blood flows. Therefore, the same amount of blood always returns to the heart as it was thrown into the vessels during systole.

The volumetric velocity in various organs may vary depending on the work of the organ and the size of its vasculature. In a working organ, the lumen of the vessels can increase and, with it, the volumetric velocity of blood movement.

Linear speed The movement of blood is called the path traveled by blood per unit of time. The linear velocity (V) reflects the speed of movement of blood particles along the vessel and is equal to the volumetric velocity (Q) divided by the cross-sectional area of the blood vessel:

Its value depends on the lumen of the vessels: the linear velocity is inversely proportional to the cross-sectional area of the vessel. The wider the total lumen of the vessels, the slower the movement of blood, and the narrower it is, the greater the speed of blood movement (Fig. 2). As the arteries branch, the speed of movement in them decreases, since the total lumen of the branches of the vessels is greater than the lumen of the original trunk. In an adult, the lumen of the aorta is approximately 8 cm 2, and the sum of the lumens of the capillaries is 500-1000 times larger - 4000-8000 cm 2. Consequently, the linear velocity of blood in the aorta is 500-1000 times greater than 500 mm/s, and in the capillaries it is only 0.5 mm/s.

Rice. 2. Signs of blood pressure (A) and linear blood flow velocity (B) in various parts of the vascular system