Hemodynamics of the heart physiology. Normal pressure in the aorta Blood pressure in the cavities of the heart

: inside arteries (blood pressure), capillaries (capillary pressure) and veins (venous pressure).

Arterial pressure depends on the strength of the contractions of the heart, the elasticity of the arteries, and mainly the resistance that peripheral vessels, arterioles and capillaries, provide to the blood flow. To a certain extent, the value blood pressure depends on the properties of blood - its viscosity, which determines the internal resistance, as well as its amount in the body.

During the contraction (systole) of the left ventricle, about 70 ml of blood is ejected into the aorta; this amount of blood cannot immediately pass through the capillaries, and therefore the elastic aorta is somewhat stretched, and the blood pressure in it rises (systolic pressure). During diastole, when the aortic valve of the heart is closed, the walls of the aorta and large vessels, contracting under the influence of their own elasticity, push the excess of blood in these vessels into the capillaries; pressure gradually decreases and by the end of diastole reaches a minimum value (diastolic pressure). The difference between systolic and diastolic pressure is called pulse pressure.

Capillary pressure depends on the blood pressure in the arterioles, the number of currently functioning capillaries and their walls.

The value of venous pressure depends on the tone of the venous vessels and the blood pressure in the right atrium. As you move away from the heart blood pressure decreases. So, for example, in the aorta, the blood pressure is 140/90 mm Hg. Art. (the first number means systolic pressure, the second - diastolic), in large arterial vessels - 110/70 mm Hg. Art. In the capillaries, blood pressure decreases from 40 mm Hg. Art. up to 10-15 mm Hg. Art. In the superior and inferior vena cava and large veins of the neck, the pressure may be negative.

Blood pressure regulation. Blood pressure ensures the movement of blood through the capillaries of the body, the implementation of metabolic processes between the capillaries and the intercellular fluid, and ultimately the normal course of metabolic processes in tissues.

The constancy of blood pressure is maintained by the principle of self-regulation. According to this principle, any deviation of any vital function from the norm is an incentive to return it to normal. normal level.

Any deviation of blood pressure towards increase or decrease causes excitation of special baroreceptors located in the walls of blood vessels. Their accumulation is especially large in the aortic arch, carotid sinus, vessels of the heart, brain, etc. Excitations from afferent nerve fibers enter the vasomotor center located in medulla oblongata, and change it. From here, impulses are sent to the blood vessels, changing the tone vascular wall and thus the amount of peripheral resistance to blood flow. At the same time, the activity of the heart also changes. Due to these influences, the deviated blood pressure returns to normal levels.

In addition, the vasomotor center is influenced by special substances produced in various organs (the so-called humoral effects). Thus, the level of tonic excitation of the vasomotor center is determined by the interaction of two types of influences on it: nervous and humoral. Some influences lead to an increase in tone and an increase in blood pressure - the so-called pressor influences; others - reduce the tone of the vasomotor center and thus have a depressant effect.

Humoral regulation of the level of blood pressure is carried out in the peripheral vessels by acting on the walls of the vessels of special substances (adrenaline, norepinephrine, etc.).

Methods for measuring and recording blood pressure. There are direct and indirect methods for measuring blood pressure. direct method in clinical practice used to measure venous pressure (see). In healthy people, venous pressure is 80-120 mm of water. Art. The most common method of indirect measurement of blood pressure is the Korotkov auscultatory method (see Sphygmomanometry). During the study, the patient sits or lies. The hand is retracted to the side with the flexion surface up. The device is installed in such a way that the artery on which blood pressure is measured and the device are at the level of the heart. Air is pumped into a rubber cuff put on the subject and connected to a pressure gauge. At the same time, with the help of a stethoscope, the artery is listened below the place where the cuff is applied (usually in the cubital fossa). Air is pumped into the cuff until the lumen of the artery is completely compressed, which corresponds to the cessation of listening to the tone on the artery. Then, air is gradually released from the cuff and the readings of the manometer are monitored. As soon as the systolic pressure in the artery exceeds the pressure in the cuff, the blood passes with force through the compressed area of ​​the vessel, and the noise of moving blood is easily heard. This moment is noted on the pressure gauge scale and is considered as an indicator of systolic blood pressure. With further release of air from the cuff, the obstruction to blood flow becomes less and less, the noise gradually weakens and, finally, disappears altogether. The manometer reading at this point is considered the value of diastolic blood pressure.

Normally, blood pressure in the brachial artery of a person aged 20-40 years is on average 120/70 mm Hg. Art. With age, the value of blood pressure, especially systolic, increases due to a decrease in the elasticity of the walls of large arteries. For an approximate estimate of the height of blood pressure, depending on age, you can use the formula:
ADmax = 100 + V, where ADmax is systolic pressure (in millimeters of mercury), B is the age of the subject in years.

Systolic pressure under physiological conditions ranges from 100 to 140 mm Hg. Art., diastolic pressure - from 60 to 90 mm Hg. Art. Systolic pressure from 140 to 160 mm Hg. Art. considered dangerous in relation to the possibility of development.

Apply oscillography to registration of arterial pressure (see).

Blood pressure in various parts of the vascular system.
Mean aortic pressure maintained at a high level (about 100 mmHg) because the heart is constantly pumping blood into the aorta. On the other hand, blood pressure varies from a systolic level of 120 mmHg. Art. to a diastolic level of 80 mm Hg. Art., since the heart pumps blood into the aorta periodically, only during systole.

As the blood moves in the great circle blood circulation the average pressure is steadily decreasing, and at the confluence of the hollow veins into the right atrium, it is 0 mm Hg. Art.

Pressure in the capillaries systemic circulation decreases from 35 mm Hg. Art. at the arterial end of the capillary up to 10 mm Hg. Art. at the venous end of the capillary. On average, "functional" pressure in most capillary networks is 17 mm Hg. Art. This pressure is enough to pass a small amount of plasma through the small pores in the capillary wall, while nutrients easily diffuse through these pores to the cells of nearby tissues.

The right side of the figure shows the change pressure in various parts of the small (pulmonary) circulation. In the pulmonary arteries, pulse pressure changes are visible, as in the aorta, however, the pressure level is much lower: systolic pressure in the pulmonary artery is on average 25 mm Hg. Art., and diastolic - 8 mm Hg. Art. Thus, the average pressure in the pulmonary artery is only 16 mm Hg. Art., and the average pressure in the pulmonary capillaries is approximately 7 mm Hg. Art. At the same time, the total volume of blood passing through the lungs per minute is the same as in the systemic circulation. Low pressure in the pulmonary capillary system is necessary for the gas exchange function of the lungs.

Theoretical foundations of blood circulation

Although the explanation of many circulatory mechanisms rather complex and ambiguous, there are three main principles that determine all the functions of the circulatory system.

1. Volumetric blood flow in organs and tissues almost always regulated depending on the metabolic needs of the tissues. When cells are actively functioning, they need an increased supply of nutrients and, therefore, an increased blood supply - sometimes 20-30 times more than at rest. However, cardiac output cannot increase more than 4-7 times. This means that it is impossible to simply increase the blood flow in the body in order to satisfy the need of any tissue for increased blood supply. Instead, vessels microvasculature in every organ and tissue immediately respond to any change in the level of metabolism, namely: the consumption of oxygen and nutrients by tissues, the accumulation of carbon dioxide and other metabolites.

All these shifts directly affect small vessels, causing them to dilate or constrict, and thus control local blood flow depending on the level of metabolism.

2. Cardiac output is controlled mainly the sum of all local tissue blood flows. From the capillary networks of peripheral organs and tissues, blood immediately returns to the heart through the veins. The heart automatically responds to increased blood flow by immediately pumping more blood into the arteries. Thus, the work of the heart depends on the needs of tissues for blood supply. This is facilitated by specific nerve signals that enter the heart and regulate its pumping function reflexively. 3. In general, systemic arterial pressure is controlled independently of the regulation of local tissue blood flow and cardiac output.

In the cardiovascular system there are effective mechanisms for regulating blood pressure. For example, every time the pressure is below the normal level (100 mmHg), within seconds, reflex mechanisms cause changes in the activity of the heart and the state of the vessels, aimed at returning blood pressure to normal levels. Nerve signals contribute to: (a) an increase in the strength of heart contractions; (b) narrowing of venous vessels and movement of blood from a capacious venous bed to the heart; (c) constriction of arterioles in most peripheral organs and tissues, which impedes the outflow of blood from large arteries and maintains a high level of pressure in them.

In addition, for more long period of time(hours to days) important kidney function associated with the secretion of hormones that control blood pressure and with the regulation of circulating blood volume will be affected. So, the needs of individual organs and tissues in the blood supply are provided by various mechanisms that regulate the activity of the heart and the state of the vessels. Later in this chapter, we will analyze in detail the main mechanisms of regulation of local blood flow, cardiac output and blood pressure.

The magnitude of blood pressure is mainly determined by two conditions: the energy that is reported to the blood by the heart, and the resistance of the arterial vascular system, which has to be overcome by the flow of blood flowing from the aorta. Thus, the value of blood pressure will be different in different parts of the vascular system. The greatest pressure will be in the aorta and large arteries, in small arteries, capillaries and veins it gradually decreases, in the vena cava the blood pressure is less than atmospheric pressure. The blood pressure will also be different throughout the cardiac cycle - it will be greater at the moment of systole and less at the moment of diastole. Fluctuations in blood pressure during systole and diastole of the heart occurs only in the aorta and arteries. In arterioles and veins, blood pressure is constant throughout the cardiac cycle. The greatest pressure in the arteries is called systolic, or maximum, the smallest - diastolic, or minimum. The pressure in different arteries is not the same. It can be different even in arteries with the same diameter (for example, in the right and left brachial arteries). In most people, the value of blood pressure is not the same in the vessels of the upper and lower extremities (usually pressure in femoral artery and lower leg arteries more than in the brachial artery) due to differences in the functional state of the vascular walls. At rest in healthy adults, systolic pressure in the brachial artery, where it is usually measured, is 100-140 mm Hg. Art. (1.3-1.8 atm) In young people, it should not exceed 120-125 mm Hg. Art. Diastolic pressure is 60-80 mm Hg. Art. , and is usually 10 mm higher than half the systolic pressure. A condition in which blood pressure is low (systolic below 100 mm) is called hypotension. A persistent increase in systolic (above 140 mm) and diastolic pressure is called hypertension. The difference between systolic and diastolic pressure is called pulse pressure, usually it is 50 mm Hg. Art. Blood pressure in children is lower than in adults; in older people, due to a change in the elasticity of the walls of blood vessels, it is higher than in young people. Blood pressure in the same person is not constant. It changes even during the day, for example, it increases when eating, during emotional manifestations, during physical work. Human blood pressure is usually measured in an indirect way, which was proposed by Riva-Rocci at the end of the 19th century. It is based on determining the amount of pressure required to completely compress an artery and stop blood flow in it. To do this, a cuff is placed on the limb of the subject, connected to a rubber pear, which serves to pump air, and a pressure gauge. When air is forced into the cuff, the artery is squeezed. At the moment when the pressure in the cuff becomes higher than the systolic one, the pulsation at the peripheral end of the artery stops. The appearance of the first pulse impulse when the pressure in the cuff decreases corresponds to the value of the systolic pressure in the artery. With a further decrease in pressure in the cuff, the sounds first increase and then disappear. The disappearance of sounds characterizes the magnitude of diastolic pressure. The time during which the pressure is measured should not exceed 1 min. , as blood circulation below the cuff application site may be impaired.

• pharmachologic effect
• Pharmacokinetics
• Indications for use
• Dosage
• Side effects
• Contraindications
• Pregnancy and breastfeeding
• drug interaction
• Overdose
• Release form
• Terms and conditions of storage
• Compound

• The use of metoprolol
• Dosage forms: tartrate and succinate
• Clinical researches
• Comparison with other beta blockers
• Prices in online pharmacies
• Dosage of metoprolol for various diseases
• How to switch to bisoprolol or carvedilol
• Patient reviews
• Frequently Asked Questions and Answers
• conclusions

Metoprolol is a drug often prescribed by doctors for hypertension, coronary disease heart, chronic heart failure, as well as for the prevention of the first and recurrent heart attack. Used since the 1980s, well studied. Metoprolol exists in the form of two dosage forms: tartrate and succinate. There are differences between them that are important to understand. They are detailed below in the article. Metoprolol is classified as a beta-blocker. It reduces the effect of adrenaline and other stimulating hormones on the heart muscle. Due to this, the pulse becomes less frequent, blood pressure normalizes, and the load on the heart decreases. Below you will find instructions for use, written in an accessible language. Read the indications for use, contraindications, dosages. Find out how to take metoprolol - before or after meals, for how long, at what dosage.

Metoprolol: instructions for use

Watch also a video about the treatment of coronary artery disease and angina pectoris

How to take metoprolol

First of all, make sure that you are prescribed a drug whose active ingredient is metoprolol succinate. Today there is no reason to use obsolete tablets containing metoprolol tartrate. They need to be taken several times a day, which is inconvenient for patients. They cause blood pressure spikes. It's bad for blood vessels. Take Betaloc ZOK or Egiloc S at the dosage prescribed by your doctor and for as long as your doctor recommends. These drugs need to be taken for a long time - several years, or even for life. They are not suitable for situations where you need to quickly bring down blood pressure or relieve an attack of chest pain.

How long can metoprolol be taken?

Metoprolol should be taken for as long as the doctor instructs. Visit your doctor regularly for follow-up examinations and consultations. You can not arbitrarily take breaks, cancel the medicine or reduce its dosage. If you are taking a beta-blocker or other prescribed medicines, keep healthy lifestyle life. This is the main treatment for hypertension and cardiovascular disease. If you do not follow the recommendations for a healthy lifestyle, then over time, even the most expensive pills will stop helping.

How to take metoprolol: before meals or after?

The official instructions do not indicate how to take metoprolol - before or after meals. Authoritative site on English language(http://www.drugs.com/food-interactions/metoprolol,metoprolol-succinate-er.html) says that medications containing metoprolol succinate and tartrate should be taken with food. Food enhances the effect of the drug, compared to taking it on an empty stomach. Find out what a low-carbohydrate diet is, how it is useful for hypertension and cardiovascular disease. Discuss with your doctor if you can follow it.

Are metoprolol and alcohol compatible?

Tablets containing metoprolol tartrate are poorly tolerated, and drinking alcohol further increases their side effects. Hypotension can happen - blood pressure will drop too much. Symptoms of hypotension: dizziness, weakness, even loss of consciousness. drugs, active substance of which metoprolol succinate is compatible with reasonable alcohol consumption. You can drink alcohol only if you are able to maintain moderation. Getting drunk while taking beta-blockers is dangerous. It is advisable not to drink alcohol for the first 1-2 weeks from the start of treatment with metoprolol, as well as after increasing the dose of the drug. During these transitional periods, one should also not manage vehicles and dangerous machinery.

Prices for drugs in which the active ingredient is metoprolol succinate

Price, rub

Prices for drugs in which the active ingredient is metoprolol tartrate

Publication

Name in Russian

Espinola-Klein C, Weisser G, Jagodzinski A, Savvidis S, Warnholtz A, Ostad MA, Gori T, Munzel T. Beta-Blockers in patients with intermittent claudication and arterial hypertension: results from the nebivolol or metoprolol in arterial occlusive disease trial. Hypertension 2011, 58(2):148-54	The effect of beta-blockers on patients with intermittent claudication and high blood pressure. Results of a comparative study of nebivolol and metoprolol in circulatory disorders in peripheral arteries.	Metoprolol and nebivolol equally well help patients who have circulatory disorders in the legs. There is no difference in efficacy between drugs.
Kampus P, Serg M, Kals J, Zagura M, Muda P, Karu K, Zilmer M, Eha J. Differential effects of nebivolol and metoprolol on central aortic pressure and left ventricular wall thickness. Hypertension.2011, 57(6):1122-8.	Differences in the effect of nebivolol and metoprolol on central aortic pressure and wall thickness of the left ventricle of the heart.	Nebivolol and metoprolol similarly lower pulse rate and mean blood pressure. However, only nebivolol significantly normalizes central SBP, DBP, central pulse pressure and left ventricular wall thickness.

Publication

Name in Russian

Phillips RA, Fonseca V, Katholi RE, McGill JB, Messerli FH, Bell DS, Raskin P, Wright JT Jr, Iyengar M, Anderson KM, Lukas MA, Bakris GL. Demographic analyzes of the effects of carvedilol vs metoprolol on glycemic control and insulin sensitivity in patients with type 2 diabetes and hypertension in the Glycemic Effects in Diabetes Mellitus: Carvedilol-Metoprolol Comparison in Hypertensives (GEMINI) study. Journal of the CardioMetabolic Syndrome 10/2008; 3(4):211-217.	A demographic analysis of the effect of carvedilol and metoprolol on glycemic control and insulin sensitivity in patients with type 2 diabetes and hypertension. Data from the GEMINI study.	In patients with type 2 diabetes, carvedilol has a better metabolic effect than metoprolol. However, the study used metoprolol tartrate and not succinate.
Acikel S, Bozbas H, Gultekin B, Aydinalp A, Saritas B, Bal U, Yildirir A, Muderrisoglu H, Sezgin A, Ozin B. Comparison of the efficacy of metoprolol and carvedilol for preventing atrial fibrillation after coronary bypass surgery. International Journal of Cardiology 2008, 126(1):108-113.	Comparison of the effectiveness of metoprolol and carvedilol in preventing arterial fibrillation after coronary bypass surgery.	In patients undergoing coronary bypass surgery, carvedilol is better at preventing atrial fibrillation than metoprolol succinate.
Remme WJ, Cleland JG, Erhardt L, Spark P, Torp-Pedersen C, Metra M, Komajda M, Moullet C, Lukas MA, Poole-Wilson P, Di Lenarda A, Swedberg K. Effect of carvedilol and metoprolol on the mode of death in patients with heart failure. European Journal of Heart Failure 2007, 9(11):1128-1135.	Influence of carvedilol and metoprolol on the causes of mortality in patients with heart failure.	In patients with heart failure, carvedilol is better at reducing all-cause mortality than metoprolol tartrate, and especially stroke mortality.

It is possible that competing beta-blockers are superior to metoprolol in efficacy. However, metoprolol succinate extended-release tablets also work well. Doctors are conservative. They are in no hurry to replace the drugs that they have long been accustomed to prescribing to patients with others. Moreover, metoprolol preparations have a relatively affordable price. In pharmacies, the demand for tablets Betalok ZOK, Egilok S, Metoprolol-Ratiopharm, if it falls, then slowly, or remains stably high.

Dosage of metoprolol for various diseases

Metoprolol is contained in tablets in the form of one of two salts - tartrate or succinate. They act differently, provide a different rate of entry of the active substance into the blood. Therefore, for fast-acting tablets of metoprolol tartrate, one dosing regimen, and for the "slow" metoprolol succinate - another. Please note that metoprolol tartrate is not indicated in heart failure.

Disease

Metoprolol succinate extended-release tablets

Metoprolol tartrate: fast-acting tablets

arterial hypertension	50-100 mg once a day. If necessary, the dose can be increased to 200 mg per day, but it is better to add another antihypertensive agent - a diuretic, a calcium antagonist, ACE inhibitor.	25–50 mg twice a day, morning and evening. If necessary, the dose can be increased to 100-200 mg per day or other drugs that lower blood pressure can be added.
angina pectoris	100-200 mg once a day. If necessary, another antianginal drug may be added to therapy.	The initial dose is 25-50 mg, taken 2-3 times a day. Depending on the effect, this dose can be gradually increased to 200 mg per day or another angina medicine can be added.
Stable chronic heart failure functional class II	The recommended starting dose is 25 mg once daily. After two weeks of treatment, the dose may be increased to 50 mg once daily. Further - doubling every two weeks. The maintenance dose for long-term treatment is 200 mg once daily.	Not shown

• Causes, symptoms, diagnosis, medications and folk remedies from CH
• Diuretic drugs for HF edema: details
• Frequently asked questions about HF - fluid and salt restriction, shortness of breath, diet, alcohol, disability
• Heart failure in the elderly: features of treatment

Watch also video:

Stable chronic heart failure III-IV functional class	It is recommended to start with a dose of 12.5 mg (1/2 tablet of 25 mg) once a day for the first two weeks. The dose is selected individually. After 1-2 weeks from the start of treatment, the dose may be increased to 25 mg once a day. Then, after another 2 weeks, the dose can be increased to 50 mg once a day. And so on. For patients who tolerate the beta-blocker well, the dose can be doubled every 2 weeks up to a maximum dose of 200 mg once daily.	Not shown
Heart rhythm disorders	100-200 mg once a day.	The initial dose is 2-3 times a day, 25-50 mg. If necessary, the daily dose can be gradually increased to 200 mg / day or another agent that normalizes the heart rhythm can be added.
Supportive care after myocardial infarction	The target dose is 100-200 mg per day, in one or two doses.	The usual daily dose is 100–200 mg divided into two divided doses, morning and evening.
Functional disorders of cardiac activity, accompanied by tachycardia	100 mg once a day. If necessary, the dose can be increased to 200 mg per day.	The usual daily dose is 50 mg twice a day, morning and evening. If necessary, it can be increased to 2 times 100 mg.
Prevention of migraine (headache) attacks	100–200 mg once a day	The usual daily dose is 100 mg divided into two divided doses, morning and evening. If necessary, it can be increased to 200 mg / day, also divided into 2 doses.

Note on the dosage of metoprolol succinate in heart failure. If the patient develops bradycardia, i.e., the pulse drops below 45-55 beats per minute, or the "upper" blood pressure is below 100 mm Hg. Art., then you may need to temporarily reduce the dose of the drug. At the beginning of treatment, there may be arterial hypotension. However, after some time, in many patients, the body adapts, and they normally tolerate therapeutic doses of the drug. Drinking alcohol increases the side effects of metoprolol, so it is better to abstain from alcohol.

How to switch to bisoprolol or carvedilol

It may happen that the patient will need to switch from metoprolol to bisoprolol (Concor, Biprol or another) or carvedilol. The reasons may be different. Theoretically, switching from one beta-blocker to another does not provide significant benefits. In practice, the gain may appear. Because the effectiveness and tolerability of drugs for each person is individual. Or the usual metoprolol tablets may simply disappear from the market, and they will have to be replaced with another drug. The table below may be helpful to you.

Source - DiLenarda A, Remme WJ, Charlesworth A. Exchange of beta-blockers in heart failure patients. Experiences for the poststudy phase of COMET (the Carvedilol or Metoprolol European Trial). European Journal of Heart Failure 2005; 7:640-9.

The table shows metoprolol succinate. For metoprolol tartrate in fast release tablets, the equivalent total daily dose is about 2 times higher. Bisoprolol is taken 1 time per day, carvedilol - 1-2 times a day.

Patient reviews

Metoprolol succinate extended-release tablets cause side effects much less frequently than fast-acting tartrate. Not surprisingly, reviews of controlled release drugs (Egiloc C, Betaloc LOK) are much more positive than fast-acting drugs in which active substance- metoprolol tartrate.

If you have high blood pressure and both prediabetes or type 2 diabetes, then you need to study and follow a type 2 diabetes treatment program. This technique normalizes blood pressure and sugar. The glucometer and tonometer will show you the first results in 2-3 days. All this without insulin shots, fasting and low-calorie diets.

Read the article "Causes of hypertension and how to eliminate them". Be examined, as it is written there, and then follow the recommendations for treatment. With a high probability, you will be able to maintain normal pressure without drugs, and you will not have to experience their side effects.

Heart problems do not occur due to a lack of metoprolol in the body. The real reason is the lack of nutrients that the heart needs for its work. First of all, it is magnesium and coenzyme Q10. Try taking these drugs along with a beta blocker. Surely you will feel better. Also pay attention to your diet. Switch from junk fast food to natural products.

Proven effective and cost-effective blood pressure supplements:

• Magnesium + Vitamin B6 from Source Naturals;
• Taurine from Jarrow Formulas;
• Fish oil from Now Foods.

Read more about the technique in the article "Treatment of hypertension without drugs". How to order hypertension supplements from the USA - download instructions. Get your blood pressure back to normal without the harmful side effects that Noliprel and other "chemical" pills cause. Improve heart function. Become calmer, get rid of anxiety, sleep like a baby at night. Magnesium with vitamin B6 works wonders for hypertension. You will have excellent health, to the envy of your peers.

Frequently Asked Questions and Answers

Below are answers to questions that often arise in patients taking metoprolol for high blood pressure and cardiovascular disease.

Metoprolol or Betaloc ZOK: which is better?

Betaloc ZOK is tradename medicines whose active ingredient is metoprolol succinate. It cannot be said that metoprolol is better than Betaloc ZOK, or vice versa, because they are one and the same. Betaloc ZOK is better than any tablet containing metoprolol tartrate. The reasons for this are detailed above. Metoprolol tartrate today can be considered an outdated drug.

Metoprolol or Concor: which is better?

In mid-2015, a study was completed that compared the effectiveness of metoprolol succinate and Concor (bisoprolol) in the treatment of hypertension. It turned out that both drugs equally lower blood pressure and are well tolerated. Unfortunately, there is no reliable information which of these drugs is better for patients with heart failure, coronary artery disease and angina pectoris. Which is better: Concor, Betalok ZOK or Egilok S? Leave the decision of this issue at the discretion of your attending physician. However, you should not take pills, the active ingredient of which is metoprolol tartrate. They are definitely worse than the drugs listed above.

Is metoprolol good for high blood pressure?

Metoprolol succinate helps with pressure no worse than other modern beta-blockers - bisoprolol, nebivolol, carvedilol. There is no reliable information which of these drugs is better than others. However, it is known for certain that metoprolol tartrate is an outdated medicine that is best not to be used. These tablets must be taken several times a day, which is inconvenient for patients. They cause significant jumps in blood pressure. It's bad for blood vessels. Metoprolol tartrate does not sufficiently reduce the risk of heart attack and other complications of hypertension.

If your doctor has prescribed you metoprolol for blood pressure, then take Betaloc ZOK or Egiloc C. As a rule, these drugs should be used together with other drugs for hypertension that are not beta-blockers. Taking multiple drugs at low doses is better than taking a single drug at a high dosage. Remember that the main treatment for hypertension is a healthy lifestyle. If you don't follow the recommendations for nutrition, physical activity, and stress management, soon even the most expensive pills won't work.

Can this beta-blocker and lisinopril be taken together?

Yes, metoprolol and lisinopril can be taken together as directed by your doctor. These are compatible drugs. Do not take any of the medicines listed in this article on your own. Find an experienced doctor to select the best high blood pressure medication for you. Before you are prescribed medication, you need to pass tests and undergo an examination. Revisit your doctor at least once every few months to adjust your medication regimen based on past treatment results.

I was prescribed the medicine metoprolol (Egilok C) for pressure. I started taking it - my eyesight fell and I often get up at night to go to the toilet. Also, ulcers appeared on the legs, they do not heal well. it side effects tablets?

No, Egilok tablets have nothing to do with it. Rather, you are exhibiting complications of type 2 diabetes. Read the article "Symptoms of Diabetes in Adults", then go to the laboratory to take blood sugar tests. If you have diabetes, treat it.

How quickly does blood pressure drop after taking metoprolol?

Tablets, the active substance of which is metoprolol succinate, act smoothly. They are not suitable if you need to quickly stop a hypertensive crisis. Preparations that contain metoprolol tartrate begin to lower blood pressure after 15 minutes. The full effect develops in 1.5-2 hours and lasts about 6 hours. If more is required fast remedy, then study the article "How to provide emergency care in a hypertensive crisis.

Is metoprolol compatible with ... such and such a drug?

Read the instructions for the drug you are interested in. Find out which group it belongs to. It can be a diuretic (diuretic), an ACE inhibitor, an angiotensin-II receptor blocker, a calcium antagonist (calcium channel blocker). Metoprolol is compatible with all the listed groups of drugs for hypertension. For example, you are interested in Prestarium. In the instructions, find that it is an ACE inhibitor. Metoprolol is compatible with it. Indapamide is a diuretic. You can also take it with him. And so on. Usually, patients are prescribed 2-3 drugs for pressure at the same time. Read more in the article "Combined drugs for hypertension - the most powerful".

Metoprolol is a beta blocker. Do not take two beta-blockers at the same time. Therefore, do not take it together with bisoprolol (Koncon, Biprol, Bisogamma), nebivolol (Nebilet, Binelol), carvedilol, atenolol, anaprilin, etc. In general, you should not take two drugs for hypertension at the same time, which belong to the same group.

How high is the risk that psoriasis will worsen from taking Egiloc C or Betaloc ZOK?

No higher than other modern beta-blockers. There are no exact data in the literature.

I have hypertension due to nervous work, frequent scandals. The doctor prescribed metoprolol. I read that one of the side effects is depression. And I'm all on my nerves. Should I take these pills?

Depression and nervous excitement are opposites. Depression is powerlessness, apathy, melancholy. Judging by the text of the question, you are experiencing the opposite emotions. It is likely that taking metoprolol will have a sedative effect, and this will benefit you.

Metoprolol lowered blood pressure, but my hands and feet began to get cold. Is this normal or should I stop taking it?

Hands and feet become cold - this is a common side effect of beta-blockers, including metoprolol. If you feel that the benefits of taking the medicine are greater than the harm from its side effects, then continue taking it. If you feel unwell, ask your doctor to select another drug for you. Keep in mind that taking beta-blockers in the first week may make you feel worse, but then the body adapts. So it's worth waiting a while if the "upper" pressure remains above 100 mmHg. Art. and the pulse does not fall below 55 beats per minute.

The doctor advised me to replace the hypertension medicine Metoprolol-Ratiopharm with the more expensive Betaloc ZOK. Is it worth it?

Yes, it's worth it. The active substance of the Ratiopharm preparation is metoprolol tartrate, and Betaloc ZOK is a succinate. The difference between them is detailed above. You are unlikely to feel how much better a new drug protects you from a heart attack. But you will surely like that now the pills can be taken only once a day. Your blood pressure will become closer to normal, its jumps during the day will decrease.

conclusions

Metoprolol is a worldwide popular pill for high blood pressure, coronary heart disease (angina pectoris), heart failure and arrhythmia. The article gives all the information about this medicine that doctors and patients may need. Links to primary sources are also provided - results clinical research, for in-depth study.

To date, only metoprolol succinate, sustained release tablets, is recommended for use. This remedy is enough to take 1 time per day. Medicines, the active substance of which is metoprolol tartrate, should be taken 2-4 times a day. They are inferior in effectiveness to other beta-blockers and are worse tolerated. If you are taking them, then discuss with your doctor if you should change to some other drug.

Perhaps bisoprolol, carvedilol and nebivolol help patients better than metoprolol succinate and even more so tartrate. This is proven by the many articles that have appeared in medical journals since the mid-2000s. However, Betaloc ZOK and Egiloc S tablets are in no hurry to give up their market share to competitors. Because doctors have been prescribing these drugs for a long time, they know their effects well and are in no hurry to give them up. Moreover, metoprolol preparations have a more attractive price compared to other beta-blockers.

• Beta blockers: general information
• Diuretic drugs
• Hypertension medications for the elderly

Angioscan - if there is nowhere to spend money

With the growing distrust of domestic medicine, the number of "enterprising" people who are trying to completely legally mislead patients by creating useless devices with a completely scientifically based principle of operation is also growing. It is obvious that Angioscan is one of such devices.

What is Angioscan?

In fact, this is a device invented long ago and introduced into medical practice - a pulse oximeter. Not a single modern intensive care unit can do without it, you probably saw it in the movies - such a clothespin on your finger. This "clothespin" is really capable of determining several basic characteristics of the pulse (its frequency, speed and filling), as well as blood oxygen saturation, but this is where its capabilities end. The pulse oximeter is mainly used in intensive care and intensive care units to monitor cardiopulmonary activity in critically ill patients.

Our "scientists" came up with the idea of ​​putting this "clothespin" on a healthy person and called it Angioscan.

It should be noted that the idea of ​​using a pulse oximeter for diagnostics is quite interesting and not devoid of common sense, why not? A complex computerized statistical analysis technique was developed to determine dozens of associated parameters. But when it became clear that all these completely existing data are useless for the doctor and the patient and are of purely scientific interest, the project had to sink into oblivion. After all diagnostic methods are created not to exist just like that, but to provide information that could be used in practice. But someone decided that the device can be moved to the masses, endowing it with "useful" qualities.

In our country, many doctors and private clinics can be interested in promoting the apparatus for material or other benefits. The main thing is to correctly present information about the device: a few small, own studies with a known result, which will give it the right to life. The patient should be given to understand that without this device it is simply impossible to live. The device also needs to be certified, “fortunately” this is not very difficult, since it is unlikely that the inspection authorities will refuse to certify a conventional pulse oximeter complete with a microcomputer. After all, not everyone knows that certificates do not always guarantee that the device is useful, but only that it is harmless and safe. But in order not to be unfounded, I will tell you in detail about all those declared qualities of angioscan in order.

Information from the official website of the developer about what an angioscan can determine.

Arterial wall stiffness – Arterial stiffness is thought to be associated with increased cardiovascular risk, that’s right. But there is another long-known fact that the stiffness of the arteries increases with age and the older the person, the higher his risk of dying. In order to understand this, do we need some kind of device? Besides, there are no methods to reduce the stiffness of the arterial wall, so why do we need to know this stiffness?

But it is known that the stiffness of the arterial wall is always higher in patients suffering from coronary artery disease or hypertension, but at the same time, stiffness does not affect the diagnosis in any way, since it cannot either confirm or exclude a particular disease. In addition, it is also impossible to influence this rigidity.

elasticity of the aorta. The aorta is the same artery, only larger, which undergoes changes with age. In the elderly and patients with atherosclerosis, its elasticity is lost, this can be seen on ultrasound of the heart or some features of blood pressure.

The tone of small resistive arteries - for example, can be determined, but just like with the stiffness of the arteries, it is not clear why this is needed.

The value of central arterial pressure, pressure in the aorta - pressure in the aorta can be determined indirectly only by means of ultrasound with Dopplerography, and then very approximately. This indicator has no practical application.

The principle of operation of the pulse oximeter is based on measuring the capillary pulse by shining a finger with a bright light source. When pulsating, small capillaries either fill with blood or empty, as a result of which the fingertip passes either more or less light, which is picked up by a special sensor from the opposite surface of the finger. As you know, the diameter of the capillaries is only 0.01-0.02 millimeters (!), And the aorta is up to 40-50 millimeters. It is not difficult to guess that it is possible to reliably determine the pressure in the aorta by capillary pressure only mathematically, because the diameter of these vessels differs by tens of thousands of times. To do this, you need to use mathematical or physical formulas with coefficients that a priori cannot be the same for different people, because we are not talking about a water pipe, but about a complex, changeable biological system.

The state of endothelial function in the area of ​​small resistive arteries (microcirculation system) and large arteries of the muscular type - at present, the detection of endothelial dysfunction is possible only by determining the level of "endothelin 1" in the blood. At the same time, you are unlikely to find a laboratory nearby that deals with the determination of endothelin 1, and not only because it is an expensive pleasure, but because it is of purely scientific interest. If Angioscan is able to determine dysfunction, then indirectly and very approximately with an error of "plus or minus bast shoes". Most likely, this method is based on how the vessels react to a short-term "light stroke". It's interesting, but nothing more.

The ability of endothelial cells to synthesize nitric monoxide, the most powerful anti-atherogenic agent, is hard to believe, but, for example, a healthy, young or old man, which was examined on an angioscan and it will be revealed that endothelial cells synthesize nitric oxide poorly. It would never occur to a sane doctor to prescribe him some kind of treatment, and the fact that in sick people this indicator will be bad anyway is beyond doubt. It can be hypothesized that this parameter may even be derived from the stiffness of the artery - the stiffer the artery, the older the patient and the worse he produces nitric monoxide.

The duration of systole, the duration of the expulsion of blood by the left ventricle is a brilliant development, if not for the fact that no one uses this indicator anywhere, because it has no practical application. But if anyone is very interested, then the same can be done using a conventional phonendoscope or pulse palpation.

Amplitude and time ratios of early and late systolic waves - well, everything is clear here, because it is written for patients - long, abstruse and not clear. Even a specialist cannot understand what is at stake. This phenomenon is not described in any of the existing recommendations of the world, and even more so, what should be done by the doctor or the patient in case of violation of this very ratio. Probably, a hotel device will soon appear that will interpret this indicator for the layman.

The augmentation index (the contribution of the late or reflected wave to the value of pulse pressure) - for those who understand what was discussed in the previous paragraph, it will not be difficult to understand this. Everything is very clear. But seriously, this augmentation is a maximum of scientific interest for some regular meaningless dissertation.

Saturation index (saturation of hemoglobin with oxygen) - or oximetry, this is the pure truth, this pulse oximeter can. The indicator is certainly important, according to the level of saturation, resuscitators usually determine when it is necessary to connect the patient to a ventilator (artificial lung ventilation) and the effectiveness of its implementation. Saturation is determined by determining the color of the fingertip, you probably know that when a person suffocates, he turns blue. A pulse oximeter or angioscan captures shades of red and blue, thus determining blood oxygen saturation. In general, if you breathe, you don’t have shortness of breath at rest and, God forbid, you don’t turn blue, then you can understand for yourself that everything is in order with saturation.

To determine the stress index, to check the efficiency of the baroreceptor center is another notion of the creators of angioscan, nothing useful can be learned from this. Usually, the work of the baroreceptor center is checked by pressure and pulse in the standing, lying and sitting positions. The need for such a check with a doctor occurs every few months.

Find out the age of the vascular system - you can still go to a fortuneteller and listen to the cuckoo. Imagine that a person is 45 years old, and the device showed 55, all that remains is to go and drown himself. Or a person is 70, and the angioscan showed 55, you can stop drinking pills, maybe you will be a couple more years younger.

Check the correctness of the therapy, and what effect the drugs prescribed to the patient have on the cardiovascular system and biological additives(BAA). At arterial hypertension treatment is monitored by measuring blood pressure, in coronary heart disease (CHD) - by the disappearance of pain in the chest, reduction of edema and shortness of breath, as well as a decrease in cholesterol and glucose levels, electrocardiogram dynamics, etc.

But about dietary supplements - this is a brilliant marketing notion, at a time when traditional medicine treat dietary supplements, to put it mildly, with caution, this medical device, it turns out, can evaluate the effectiveness of their action. And here it turns out that the creators and doctors who promote angioscan are not at all against dietary supplements, but even welcome their use. This calls into question if not the competence, then the sanity of these doctors. Dietary supplements are a separate issue.

Conduct a breath test - spend on health, just that it will make it difficult to understand. If you breathe often - the saturation will be greater, hold your breath - it will decrease.

Warn the patient about the possibility of developing cardiovascular diseases before they begin to develop. Why are doctors worse than angioscan in this regard? After 50-60 years, the likelihood of heart disease increases and every second or third person has something to be found. Come to the appointment every year, starting at the age of 45, and they will also be able to warn you in time. And then, after all, how our people act: they endure 3-5 years, and then they are brought in by ambulance.

Early detection of the possibility of kidney problems and endothelial dysfunction in the last third of pregnancy. In order to "check the kidneys" you need a urine and blood test and nothing more, if the problem is serious, it will be identified.

As you can see from the volume of this article, Angioscan is capable of a lot, but it is difficult to single out at least one indicator from all of this that could be used in practice to improve the health and quality of life of patients.

The only positive side of this device is that the patient with cardiovascular disease and disregard for himself when bad results are revealed according to angioscan, he will finally run to the doctor. I agree that this is not enough and can overshadow all the rest of his "useful" qualities. But the opposite situation may also arise - a young, healthy, but very hypochondriac patient will decide that he is terminally ill, and the doctors will not be able to do anything about it.

Finally, one piece of advice: if you are nevertheless offered to be examined on an angioscan, ask your doctor how this examination will affect your treatment or diagnosis. Treat such devices with care.

You have the information, but the decision is yours.

This article is the personal opinion of Dr. Lieberman.

Circulation is the movement of blood through the vascular system. It provides gas exchange between the body and the external environment, metabolism between all organs and tissues, humoral regulation of various functions of the body and the transfer of heat generated in the body. Blood circulation is a process necessary for the normal activity of all body systems, primarily the central nervous system. The section of physiology devoted to the laws of blood flow through the vessels is called hemodynamics, the basic laws of hemodynamics are based on the laws of hydrodynamics, i.e. theory of fluid motion in tubes.

The laws of hydrodynamics are applicable to the circulatory system only within certain limits and only with approximate accuracy. Hemodynamics is a branch of physiology about the physical principles underlying the movement of blood through the vessels. The driving force of blood flow is the pressure difference between individual sections of the vascular bed. blood flows from an area of ​​higher pressure to an area of ​​lower pressure. This pressure gradient serves as a source of force that overcomes hydrodynamic resistance. Hydrodynamic resistance depends on the size of the vessels and the viscosity of the blood.

Basic hemodynamic parameters .

1. Volumetric blood flow rate. Blood flow, i.e. the volume of blood passing per unit time through the blood vessels in any section of the bloodstream is equal to the ratio of the difference in average pressures in the arterial and venous parts of this section (or in any other parts) to the hydrodynamic resistance. Volumetric blood flow velocity reflects the blood supply to any organ or tissue.

In hemodynamics, this hydrodynamic indicator corresponds to the volumetric blood velocity, i.e. the amount of blood flowing through the circulatory system per unit of time, in other words, the minute volume of blood flow. Since the circulatory system is closed, the same amount of blood passes through any cross section of it per unit time. The circulatory system consists of a system of branching vessels, so the total lumen grows, although the lumen of each branch gradually decreases. Through the aorta, as well as through all arteries, all capillaries, all veins, the same volume of blood passes per minute.

2. The second hemodynamic indicator - linear velocity of blood .

You know that the flow rate of a fluid is directly proportional to pressure and inversely proportional to resistance. Consequently, in tubes of different diameters, the blood flow rate is greater, the smaller the cross section of the tube. AT circulatory system the narrowest point is the aorta, the widest is the capillaries (recall that we are dealing with the total lumen of the vessels). Accordingly, the blood in the aorta moves much faster - 500 mm / s than in the capillaries - 0.5 mm / s. In the veins, the linear velocity of blood flow increases again, since when the veins merge with each other, the total lumen of the bloodstream narrows. In the hollow veins, the linear velocity of blood flow reaches half the rate in the aorta (Fig.).

The linear velocity is different for blood particles moving in the center of the flow (along the longitudinal axis of the vessel) and near the vascular wall. In the center of the vessel, the linear velocity is maximum, near the vessel wall it is minimal due to the fact that the friction of blood particles against the wall is especially high here.

The resultant of all linear velocities in different parts of the vascular system is expressed as blood circulation time . She is at healthy person at rest is 20 seconds. This means that the same particle of blood passes through the heart every minute 3 times. With intense muscular work, the blood circulation time can be reduced to 9 seconds.

3. Vascular resistance - third hemodynamic index. Flowing through the tube, the liquid overcomes the resistance that arises due to the internal friction of the liquid particles between themselves and against the tube wall. This friction will be the greater, the greater the viscosity of the fluid, the narrower its diameter and the greater the flow velocity.

Under viscosity usually understand internal friction, i.e. forces affecting the flow of a fluid.

However, it should be taken into account that there is a mechanism that prevents a significant increase in resistance in the capillaries. It is due to the fact that in the smallest vessels (less than 1 mm in diameter), erythrocytes line up in the so-called coin columns and, like a snake, move along the capillary in the plasma shell, almost without contact with the walls of the capillary. As a result, blood flow conditions are improved, and this mechanism partially prevents a significant increase in resistance.

Hydrodynamic resistance also depends on the size of the vessels, their length and cross section. In summary, the equation describing vascular resistance is the following (Poiseuille formula):

R \u003d 8ŋL / πr 4

where ŋ is the viscosity, L is the length, π = 3.14 (pi), r is the radius of the vessel.

Blood vessels offer significant resistance to blood flow, and the heart has to spend most of its work to overcome this resistance. The main resistance of the vascular system is concentrated in that part of it where the branching of the arterial trunks into the smallest vessels occurs. However, the smallest arterioles present the maximum resistance. The reason is that the arterioles, having almost the same diameter as the capillaries, are generally longer and the speed of blood flow in them is higher. In this case, the value of internal friction increases. In addition, arterioles are capable of spasm. The total resistance of the vascular system increases all the time with distance from the base of the aorta.

Blood pressure in the vessels. This is the fourth and most important hemodynamic indicator, as it is easy to measure.

If a manometer sensor is inserted into a large artery of an animal, the device will detect pressure that fluctuates in the rhythm of heartbeats around an average value of approximately 100 mm Hg. The pressure existing inside the vessels is created by the work of the heart, which pumps blood into the arterial system during systole. However, even during diastole, when the heart is relaxed and does not work, the pressure in the arteries does not drop to zero, but only drops slightly, giving way to a new rise during the next systole. Thus, the pressure ensures a continuous flow of blood, despite the intermittent work of the heart. The reason is the elasticity of the arteries.

The value of blood pressure determined by two factors: the amount of blood pumped by the heart and the resistance that exists in the system:

It is clear that the pressure distribution curve in the vascular system should be a mirror reflection of the resistance curve. So, in the subclavian artery of a dog, P = 123 mm Hg. Art. in the shoulder - 118 mm, in the capillaries of the muscles - 10 mm, in the facial vein - 5 mm, in the jugular - 0.4 mm, in the superior vena cava -2.8 mm Hg.

Among these data, the negative value of pressure in the superior vena cava attracts attention. It means that in the large venous trunks directly adjacent to the atrium, the pressure is less than atmospheric pressure. It is created by suction. chest and the heart itself during diastole and promotes the movement of blood to the heart.

Basic principles of hemodynamics

Other from the section: ▼

The doctrine of the movement of blood in the vessels is based on the laws of hydrodynamics - the doctrine of the movement of fluids. The movement of fluid through pipes depends: a) on the pressure at the beginning and end of the pipe b) on the resistance in this pipe. The first of these factors promotes, and the second - hinders the movement of fluid. The amount of fluid flowing through the pipe is directly proportional to the pressure difference at the beginning and end of it and inversely proportional to the resistance.

In the circulatory system, the volume of blood that flows through the vessels also depends on the pressure at the beginning of the vascular system (in the aorta - P1) and at the end (in the veins flowing into the heart - P2), as well as on the resistance of the vessels.

The volume of blood flowing through each section of the vascular bed per unit of time is the same. This means that in 1 min through the aorta, or pulmonary arteries, or the total cross section, carried out at any level of all arteries, capillaries, veins, the same amount of blood flows. This is the IOC. The volume of blood flowing through the vessels is expressed in milliliters per minute.

The resistance of the vessel depends, according to the Poiseuille formula, on the length of the vessel (l), blood viscosity (n) and the radius of the vessel (r).

According to the equation, the maximum resistance to blood flow should be in the thinnest blood vessels - arterioles and capillaries, namely: about 50% of the total peripheral resistance falls on arterioles and 25% on capillaries. Less resistance in capillaries is explained by the fact that they are much shorter than arterioles.

Resistance is also affected by blood viscosity, which is determined primarily by formed elements and to a lesser extent by proteins. In humans, it is “C-5. The shaped elements are localized near the walls of the vessels, move due to friction between themselves and the wall at a lower speed than those that are concentrated in the center. They play a role in the development of resistance and blood pressure.

Hydrodynamic resistance the entire vascular system cannot be measured directly. However, it can be easily calculated using the formula, remembering that P1 in the aorta is 100 mm Hg. Art. (13.3 kPa), and P2 in the vena cava is about 0.

Basic principles of hemodynamics. Vessel classification

Hemodynamics is a branch of science that studies the mechanisms of blood movement in the cardiovascular system. It is part of the hydrodynamics branch of physics that studies the movement of fluids.

According to the laws of hydrodynamics, the amount of fluid (Q) flowing through any pipe is directly proportional to the pressure difference at the beginning (P1) and at the end (P2) of the pipe and inversely proportional to the resistance (P2) to the fluid flow:

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 vena cava into the heart, is close to zero. In this case, the equation can be written as:

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

It follows from this equation that P \u003d Q * R, i.e., pressure (P) at the aortic orifice is directly proportional to the volume of blood ejected by the heart in the artery per minute (Q) and the value of peripheral resistance (R). Aortic pressure (P) and minute volume (Q) can be measured directly. Knowing these values, peripheral resistance is calculated - the most important indicator of the state 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 (R) is determined by the Poiseuille formula:

where l is the 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 radius of the tube.

The vascular system consists of many individual tubes connected in parallel and in series. When the tubes are connected in series, their total resistance is equal to the sum of the resistances of each tube:

R=R1+R2+R3+. +Rn

When the tubes are connected in parallel, their total resistance is calculated by the formula:

R=1/(1/R1+1/R2+1/R3+.+1/Rn)

It is impossible to accurately determine the vascular resistance using these formulas, since the geometry of the vessels changes due to the contraction of the vascular muscles. Blood viscosity is also not a constant value. For example, if blood flows through vessels less than 1 mm in diameter, the viscosity of the blood decreases significantly. The smaller the diameter of the vessel, the lower the viscosity of the blood flowing in it. This is due to the fact that in the blood, along with plasma, there are shaped elements that are located in the center of the flow. The parietal layer is plasma, the viscosity of which is much less than the viscosity of whole blood. The thinner the vessel, the greater part of its cross-sectional area is occupied by a layer with a minimum viscosity, which reduces the overall value of blood viscosity. The theoretical calculation of capillary resistance is impossible, since normally only a part of the capillary bed is open, the rest of the capillaries are reserve and open as the metabolism in tissues increases.

It can be seen from the above equations that a capillary with a diameter of 5–7 µm should have the greatest resistance value. However, due to the fact that a huge number of capillaries are included in the vascular network, through which blood flows, in parallel, their total resistance is less than the total resistance of arterioles.

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

Arterioles are thin vessels (diameter 15-70 microns). The wall of these vessels contains a thick layer of circularly located smooth muscle cells, with the reduction of which the lumen of the vessel can significantly decrease. This sharply increases the resistance of arterioles. Changing the resistance of arterioles changes the level of blood pressure in the arteries. In the case of an increase in the resistance of arterioles, the outflow of blood from the arteries decreases and the pressure in them increases. The decrease in arteriole tone increases the outflow of blood from the arteries, which leads to a decrease in blood pressure. 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 - "faucets of the cardiovascular system" (I. M. Sechenov). 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.

So, arterioles play a dual role: they participate in maintaining the level of general arterial pressure necessary for the body and in regulating the magnitude of local blood flow through a particular organ or tissue. The value of the organ blood flow corresponds to the organ's need for oxygen and nutrients, determined by the level of the organ's working activity.

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

The resistance in various vessels can be judged by the difference in blood pressure at the beginning and end of the vessel: the higher the resistance to blood flow, the greater the force expended on its movement through the vessel and, therefore, the greater the pressure drop throughout this vessel. As direct measurements of blood pressure in different vessels show, the pressure along large and medium arteries drops by only 10%, and in arterioles and capillaries - by 85%. This means that 10% of the energy expended by the ventricles to expel blood is spent on the promotion of blood in large and medium arteries, and 85% is spent on the promotion of blood in arterioles and capillaries.

Knowing the volumetric velocity of blood flow (the amount of blood flowing through the cross section of the vessel), measured in milliliters per second, it is possible to calculate the linear velocity of blood flow, which is expressed in centimeters per second. 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:

The linear speed calculated from this formula is the average speed. In reality, the linear velocity is different for blood particles moving in the center of the flow (along the longitudinal axis of the vessel) and near the vessel wall. In the center of the vessel, the linear velocity is maximum, near the vessel wall it is minimal due to the fact that the friction of blood particles against the wall is especially high here.

The volume of blood flowing in 1 min through the aorta or vena cava and through the pulmonary artery or pulmonary veins, is the same. The outflow of blood from the heart corresponds to its inflow. From this it follows that the volume of blood flowing in 1 minute through the entire arterial and entire venous system of the systemic and pulmonary circulation is the same. With a constant volume of blood flowing through any common section of the vascular system, the linear velocity of blood flow cannot be constant. It depends on the total width of this section of the vascular bed. This follows from the equation expressing the ratio of linear and volumetric velocity: the greater the total cross-sectional area of ​​the vessels, the lower the linear velocity of blood flow. The narrowest point in the circulatory system is the aorta. When the arteries branch, despite the fact that each branch of the vessel is narrower than the one from which it originated, an increase in the total channel is observed, since the sum of the lumens of the arterial branches is greater than the lumen of the branched artery. The greatest expansion of the channel is noted in the capillary network: the sum of the lumens of all capillaries is approximately 500-600 times greater than the lumen of the aorta. Accordingly, the blood in the capillaries moves 500-600 times slower than in the aorta.

In the veins, the linear velocity of blood flow increases again, since when the veins merge with each other, the total lumen of the bloodstream narrows. In the vena cava, the linear velocity of blood flow reaches half the rate in the aorta.

Due to the fact that the blood is ejected by the heart in separate portions, the blood flow in the arteries has a pulsating character, so the linear and volumetric velocities are constantly changing: they are maximum in the aorta and pulmonary artery at the time of ventricular systole and decrease during diastole. In capillaries and veins, the blood flow is constant, that is, its linear velocity is constant. In the transformation of pulsating blood flow into a constant, the properties of the arterial wall are important.

The continuous flow of blood throughout the vascular system determines the pronounced elastic properties of the aorta and large arteries.

In the cardiovascular system, part of the kinetic energy developed by the heart during systole is spent on stretching the aorta and large arteries extending from it. The latter form an elastic, or compression, chamber, into which a significant volume of blood enters, stretching it; at the same time, the kinetic energy developed by the heart is converted into the energy of the elastic tension of the arterial walls. When systole ends, the stretched walls of the arteries tend to escape and push blood into the capillaries, maintaining blood flow during diastole.

From the standpoint of functional significance for the circulatory system, the vessels are divided into the following groups:

1. Elastically tensile - aorta with large arteries in the systemic circulation, pulmonary artery with its branches - in a small circle, i.e. vessels of an elastic type.

2. Vessels of resistance (resistive vessels) - arterioles, including precapillary sphincters, i.e. vessels with a well-defined muscular layer.

3. Exchange (capillaries) - vessels that ensure the exchange of gases and other substances between blood and tissue fluid.

4. Shunting (arteriovenous anastomoses) - vessels that provide a "dump" of blood from the arterial to the venous vascular system, bypassing the capillaries.

5. Capacitive - veins with high extensibility. Because of this, the veins contain 75-80% of the blood.

The processes that take place in series-connected vessels that provide circulation (circulation) of blood are called systemic hemodynamics. The processes occurring in the vascular channels connected in parallel to the aorta and vena cava, providing blood supply to the organs, are called regional, or organ, hemodynamics.