Method for determining the minute volume of blood (mok) and total peripheral vascular resistance (ops). Increased peripheral vascular resistance Indicators of peripheral resistance increased

Physiological role of arterioles in blood flow regulation

On the scale of the body, the total peripheral resistance depends on the tone of the arterioles, which, along with the stroke volume of the heart, determines the value of blood pressure.

In addition, the tone of arterioles can change locally, within a given organ or tissue. A local change in the tone of arterioles, without having a noticeable effect on the total peripheral resistance, will determine the amount of blood flow in this organ. Thus, the tone of arterioles is markedly reduced in working muscles, which leads to an increase in their blood supply.

Regulation of arteriole tone

Since the change in the tone of arterioles on the scale of the whole organism and on the scale of individual tissues has completely different physiological significance, there are both local and central mechanisms of its regulation.

Local regulation of vascular tone

In the absence of any regulatory influences, an isolated arteriole, devoid of endothelium, retains a certain tone, depending on the smooth muscles... It is called the basal vascular tone. It can be influenced by such environmental factors as pH and CO 2 concentration (a decrease in the first and an increase in the second lead to a decrease in tone). This reaction turns out to be physiologically reasonable, since an increase in local blood flow following a local decrease in arteriole tone, in fact, will lead to the restoration of tissue homeostasis.

Systemic hormones that regulate vascular tone

Vasoconstrictor and vasodilating nerves

All, or almost all, of the body's arterioles receive sympathetic innervation. The sympathetic nerves have catecholamines (in most cases norepinephrine) as a neurotransmitter and have a vasoconstrictor effect. Since the affinity of β-adrenergic receptors for norepinephrine is low, the pressor effect predominates even in skeletal muscles under the action of sympathetic nerves.

Parasympathetic vasodilating nerves, the neurotransmitters of which are acetylcholine and nitric oxide, are found in the human body in two places: the salivary glands and the corpus cavernosum. In the salivary glands, their action leads to an increase in blood flow and increased filtration of fluid from the vessels into the interstitium and further to abundant secretion of saliva; in the cavernous bodies, a decrease in the tone of arterioles under the action of vasodilating nerves ensures an erection.

Participation of arterioles in pathophysiological processes

Inflammation and allergic reactions

The most important function inflammatory response- localization and lysis of a foreign agent that caused inflammation. The functions of lysis are performed by cells delivered to the inflammation focus by the blood stream (mainly neutrophils and lymphocytes. Accordingly, it is advisable to increase the local blood flow in the inflammation focus. Therefore, substances that have a powerful vasodilating effect - histamine and prostaglandin E 2 serve as "mediators of inflammation"). of the five classic symptoms of inflammation (redness, edema, fever) are caused precisely by vasodilation.Increased blood flow - hence redness; an increase in pressure in capillaries and an increase in fluid filtration from them - therefore, edema (however, an increase in wall permeability is also involved in its formation capillaries), an increase in the flow of heated blood from the core of the body - hence, heat (although here, perhaps, an increase in the metabolic rate in the focus of inflammation plays an equally important role).

However, histamine, in addition to a protective inflammatory response, is a major mediator of allergies.

This substance is secreted by mast cells when antibodies adsorbed on their membranes bind to antigens from the E.

An allergy to a substance occurs when a lot of such antibodies are accumulated against it and they are massively sorbed on mast cells throughout the body. Then, upon contact of a substance (allergen) with these cells, they secrete histamine, which causes expansion of arterioles at the site of secretion, followed by pain, redness and swelling. Thus, all variants of allergies, from rhinitis and urticaria, to Quincke's edema and anaphylactic shock, are largely associated with a histamine-dependent drop in arteriole tone. The difference is where and how massive this expansion occurs.

A particularly interesting (and dangerous) variant of allergy is anaphylactic shock. It occurs when an allergen, usually after intravenous or intramuscular injection, spreads throughout the body and causes the secretion of histamine and vasodilatation throughout the body. In this case, all capillaries are filled with blood as much as possible, but their total capacity exceeds the volume of circulating blood. As a result, the blood does not return from the capillaries to the veins and atria, the effective work of the heart becomes impossible and the pressure drops to zero. This reaction develops within a few minutes and leads to the death of the patient. The most effective measure for anaphylactic shock is intravenous administration a substance with a powerful vasoconstrictor effect - best of all norepinephrine.

Table of contents of the subject "Functions of circulatory systems and lymph circulation. Circulatory system. Systemic hemodynamics. Cardiac output.":
1. Functions of the circulatory and lymph circulation systems. Circulatory system. Central venous pressure.
2. Classification of the circulatory system. Functional classifications of the circulatory system (Folkova, Tkachenko).
3. Characteristics of the movement of blood through the vessels. Hydrodynamic characteristics of the vascular bed. Linear blood flow velocity. What is cardiac output?
4. Blood flow pressure. Blood flow rate. Diagram of the cardiovascular system (CVS).
5. Systemic hemodynamics. Hemodynamic parameters. Systemic blood pressure. Systolic, diastolic pressure. Medium pressure. Pulse pressure.

7. Cardiac output. The minute volume of blood circulation. Cardiac index. Systolic blood volume. Reserve blood volume.
8. Heart rate (pulse). The work of the heart.
9. Contractility. Contractility of the heart. Myocardial contractility. Myocardial automatism. Myocardial conductivity.
10. Membrane nature of heart automation. Pacemaker. Pacemaker. Myocardial conductivity. A true pacemaker. Latent pacemaker.

This term means total resistance of the entire vascular system the flow of blood thrown out by the heart. This relationship is described equation:

As follows from this equation, in order to calculate OPSS, it is necessary to determine the value of the systemic blood pressure and cardiac output.

Direct bloodless methods for measuring total peripheral resistance have not been developed, and its value is determined from Poiseuille equations for hydrodynamics:

where R is the hydraulic resistance, l is the length of the vessel, v is the viscosity of the blood, r is the radius of the vessels.

Since in the study of the vascular system of an animal or human, the radius of the vessels, their length and blood viscosity usually remain unknown, Franc, using a formal analogy between hydraulic and electrical circuits, led Poiseuille equation to the following form:

where Р1-Р2 are the pressure difference at the beginning and at the end of a section of the vascular system, Q is the amount of blood flow through this section, 1332 is the coefficient of conversion of resistance units into the CGS system.

Frank's equation is widely used in practice to determine vascular resistance, although it does not always reflect the true physiological relationship between volumetric blood flow, blood pressure and vascular resistance to blood flow in warm-blooded animals. These three parameters of the system are indeed related by the above ratio, but in different objects, in different hemodynamic situations and at different times, their changes can be interdependent to varying degrees. So, in specific cases, the SBP level can be determined mainly by the value of the systemic vascular resistance or mainly by the SV.

Rice. 9.3. A more pronounced increase in the resistance of the vessels of the thoracic aortic basin compared with its changes in the basin of the brachiocephalic artery during the pressor reflex.

Under normal physiological conditions OPSS is from 1200 to 1700 dyne s ¦ cm, at hypertension this value can double against the norm and be equal to 2200-3000 dyne s cm-5.

The value of OPSS consists of the sums (not arithmetic) of the resistances of the regional vascular divisions. In this case, depending on the greater or lesser severity of changes in the regional resistance of the vessels, they will accordingly receive a smaller or larger volume of blood ejected by the heart. In fig. 9.3 shows an example of a more pronounced degree of increase in the resistance of the vessels of the basin of the descending thoracic aorta in comparison with its changes in the brachiocephalic artery. Therefore, the increase in blood flow in the brachiocephalic artery will be greater than in the thoracic aorta. This mechanism is the basis of the effect of "centralization" of blood circulation in warm-blooded animals, providing in severe or threatening conditions for the body (shock, blood loss, etc.), the redistribution of blood, primarily to the brain and myocardium.

8) classification of blood vessels.

Blood vessels- elastic tubular formations in the body of animals and humans, along which the force of a rhythmically contracting heart or a pulsating vessel moves blood through the body: to organs and tissues through arteries, arterioles, arterial capillaries, and from them to the heart - through venous capillaries, venules and veins ...

Among the vessels of the circulatory system are distinguished arteries, arterioles, capillaries, venules, veins and arterio-venous anastomoses; the vessels of the microvasculature system carry out the relationship between arteries and veins. Vessels of different types differ not only in their thickness, but also in tissue composition and functional characteristics.

Arteries are the vessels through which blood flows from the heart. Arteries have thick walls that contain muscle fibers, as well as collagen and elastic fibers. They are very elastic and can shrink or expand depending on the amount of blood pumped by the heart.

Arterioles are small arteries that immediately precede the capillaries in the bloodstream. Smooth muscle fibers predominate in their vascular wall, thanks to which arterioles can change the size of their lumen and, thus, resistance.

Capillaries are the smallest blood vessels are so thin that substances can freely penetrate through their wall. Through the wall of the capillaries, nutrients and oxygen are released from the blood into the cells and the transition of carbon dioxide and other waste products from the cells into the blood.

Venules are small blood vessels that provide in a large circle the outflow of oxygen-depleted blood saturated with waste products from the capillaries into the veins.

Veins are the vessels that carry blood to the heart. The walls of the veins are less thick than the walls of the arteries and accordingly contain fewer muscle fibers and elastic elements.

9) Volumetric blood flow velocity

The volumetric flow rate of the blood (blood flow) of the heart is a dynamic indicator of the activity of the heart. The variable physical quantity corresponding to this indicator characterizes the volumetric amount of blood passing through the cross-section of the flow (in the heart) per unit of time. The volumetric blood flow rate of the heart is estimated by the formula:

CO = HR · SV / 1000,

where: HR- heart rate (1 / min), SV- systolic blood flow ( ml, l). The circulatory system, or cardiovascular system, is a closed system (see Scheme 1, Scheme 2, Scheme 3). It consists of two pumps (right heart and left heart), interconnected by successive blood vessels of the systemic circulation and blood vessels of the pulmonary circulation (vessels of the lungs). In any cumulative section of this system, the same amount of blood flows. In particular, under the same conditions, the blood flow through the right heart is equal to the blood flow through the left heart. In a person at rest, the volumetric blood flow velocity (both right and left) of the heart is ~ 4.5 ÷ 5.0 l / min... The purpose of the circulatory system is to provide continuous blood flow to all organs and tissues in accordance with the needs of the body. The heart is a pump that pumps blood through the circulatory system. Together with the blood vessels, the heart actualizes the goal of the circulatory system. Hence, the volumetric blood flow rate of the heart is a variable that characterizes the efficiency of the heart. The blood flow to the heart is controlled by the cardiovascular center and depends on a number of variables. The main ones are: the volumetric flow rate of venous blood to the heart ( l / min), end-diastolic blood flow volume ( ml), systolic blood flow ( ml), end-systolic blood flow volume ( ml), heart rate (1 / min).

10) The linear velocity of blood flow (blood flow) is a physical quantity that is a measure of the movement of blood particles that make up the flow. Theoretically, it is equal to the distance traveled by the particle of the substance that makes up the flow, in units of time: v = L / t... Here L- way ( m), t- time ( c). In addition to the linear blood flow velocity, the volumetric blood flow rate is distinguished, or volumetric blood flow velocity... Average linear velocity of laminar blood flow ( v) is estimated by integrating the linear velocities of all cylindrical layers of the flow:

v = (dP R 4 ) / (8η · l ),

where: dP- the difference in blood pressure at the beginning and at the end of a section of a blood vessel, r- vessel radius, η - blood viscosity, l - the length of the vessel section, the coefficient 8 is the result of the integration of the velocities of the blood layers moving in the vessel. Volumetric blood flow velocity ( Q) and the linear blood flow velocity are related by the relationship:

Q = vπ R 2 .

Substituting into this relation the expression for v we obtain the Hagen-Poiseuille equation ("law") for the volumetric flow rate:

Q = dP · (π R 4 / 8η · l ) (1).

Based on simple logic, it can be argued that the volumetric velocity of any flow is directly proportional to the driving force and inversely proportional to the resistance to flow. Similarly, the volumetric blood flow velocity ( Q) is directly proportional to the driving force (pressure gradient, dP), providing blood flow, and is inversely proportional to the resistance to blood flow ( R): Q = dP / R... From here R = dP / Q... Substituting into this ratio expression (1) for Q, we obtain the formula for assessing the resistance to blood flow:

R = (8η · l ) / (π R 4 ).

It can be seen from all these formulas that the most significant variable determining the linear and volumetric blood flow velocity is the lumen (radius) of the vessel. This variable is the main variable in blood flow control.

Vascular resistance

Hydrodynamic resistance is directly proportional to the length of the vessel and blood viscosity and inversely proportional to the radius of the vessel to the 4th degree, that is, it most of all depends on the lumen of the vessel. Since arterioles have the greatest resistance, OPSS depends mainly on their tone.

Distinguish between the central mechanisms of regulation of the tone of arterioles and local mechanisms of regulation of the tone of arterioles.

The former include nervous and hormonal influences, the latter - myogenic, metabolic and endothelial regulation.

The sympathetic nerves have a permanent tonic vasoconstrictor effect on the arterioles. The magnitude of this sympathetic tone depends on the impulses coming from the otbaroreceptors of the carotid sinus, aortic arch and pulmonary arteries.

The main hormones normally involved in the regulation of arteriole tone are adrenaline and noradrenaline, which are produced by the adrenal medulla.

Myogenic regulation is reduced to contraction or relaxation of vascular smooth muscles in response to changes in transmural pressure; while the voltage in their wall remains constant. This ensures the autoregulation of local blood flow - the constancy of blood flow with varying perfusion pressure.

Metabolic regulation provides vasodilatation with an increase in basal metabolism (due to the release of adenosine and prostaglandins) and hypoxia (also due to the release of prostaglandins).

Finally, endothelial cells secrete a number of vasoactive substances - nitric oxide, eicosanoids (derivatives of arachidonic acid), vasoconstrictor peptides (endothelin-1, angiotensin II) and oxygen free radicals.

12) blood pressure in different parts of the vascular bed

Blood pressure in various parts of the vascular system. The mean pressure in the aorta is kept high (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 mm Hg. 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 systemic circulation, the average pressure steadily decreases, and at the place where the vena cava flows into the right atrium, it is 0 mm Hg. Art. Capillary pressure large circle blood 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, the "functional" pressure in most capillary networks is 17 mm Hg. Art. This pressure is enough for a small amount of plasma to pass 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 in pressure in different parts of the small (pulmonary) circle of blood circulation. In the pulmonary arteries, pulse pressure changes are visible, as in the aorta, however, the pressure level is much lower: the systolic pressure in the pulmonary artery is on average 25 mm Hg. Art., and diastolic - 8 mm Hg. Art. Thus, the mean pulmonary artery pressure 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.

Disseminated intravascular coagulation (ICS-SYNDROME)

Disseminated intravascular coagulation

Disseminated intravascular coagulation (DIC)

Disseminated intravascular coagulation (disseminated intravascular coagulation)

Personality change in diseases: epilepsy, schizophrenia, traumatic and vascular brain damage.

Initiation of therapy. Training and informing the client. Specifics of Working with Resistance and Transference at the Beginning of Therapy

Influenced physical activity vascular resistance changes significantly. An increase in muscle activity leads to increased blood flow through the contracting muscles,

than the local blood flow increases 12-15 times compared with the norm (A. Dyutop et al., "No. 5m.amysy, 1962). One of the most important factors contributing to increased blood flow in muscle work, is a sharp decrease in resistance in the vessels, which leads to a significant decrease in the total peripheral resistance (see table. 15.1). The decrease in resistance begins 5-10 s after the start of muscle contraction and reaches a maximum in 1 min or later (A. Oyu! Op, 1969). This is due to reflex vasodilation, lack of oxygen in the cells of the vascular walls of working muscles (hypoxia). Muscles absorb oxygen faster during exercise than when they are at rest.

The value of peripheral resistance is different for different sites vascular bed. This is primarily due to a change in the diameter of the vessels during branching and associated changes in the nature of movement and properties of blood moving through them (blood flow velocity, blood viscosity, etc.). The main resistance of the vascular system is concentrated in its precapillary part - in small arteries and arterioles: 70-80% of the total drop in blood pressure when moving from the left ventricle to the right atrium falls on this part of the arterial bed. These. vessels are therefore called resistance vessels or resistive vessels.

Blood, which is a suspension of formed elements in a colloidal saline solution, has a certain viscosity. It was revealed that the relative viscosity of blood decreases with an increase in its flow rate, which is associated with the central location of erythrocytes in the flow and their aggregation during movement

It is also noticed that the less elastic the arterial wall (that is, the more difficult it is to stretch, for example, in atherosclerosis), the more resistance the heart has to overcome to push each new portion of blood into the arterial system and the higher the pressure in the arteries rises during systole.

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This term is understood as the total resistance of the entire vascular system to the blood flow ejected by the heart. This relationship is described by the equation:

Used to calculate the value of this parameter or its changes. To calculate the OPSS, it is necessary to determine the value of systemic arterial pressure and cardiac output.

The value of OPSS consists of the sums (not arithmetic) of the resistances of the regional vascular departments. In this case, depending on the greater or lesser severity of changes in the regional resistance of the vessels, they will accordingly receive a smaller or larger volume of blood ejected by the heart.

This mechanism is the basis of the effect of "centralization" of blood circulation in warm-blooded animals, providing in severe or threatening conditions for the body (shock, blood loss, etc.), the redistribution of blood, primarily to the brain and myocardium.

Resistance, pressure difference and flow are related by the basic hydrodynamic equation: Q = AP / R. Since the flow (Q) must be identical in each of the sequentially located sections of the vascular system, the pressure drop that occurs along each of these sections is a direct reflection of the resistance that exists in this section. Thus, a significant drop in blood pressure as blood passes through the arterioles indicates that the arterioles have significant resistance to blood flow. The average pressure decreases slightly in the arteries, as they have little resistance.

Likewise, the moderate pressure drop that occurs in capillaries is a reflection that capillaries have moderate resistance compared to arterioles.

The flow of blood through individual organs can change tenfold or more. Since mean arterial pressure is a relatively stable indicator of activity of cardio-vascular system, significant changes in the blood flow of an organ are a consequence of changes in its total vascular resistance to blood flow. Consecutively located vascular sections are combined into certain groups within the organ, and the total vascular resistance of the organ should be equal to the sum of the resistances of its series-connected vascular sections.

Since arterioles have a significantly greater vascular resistance compared to other parts of the vascular bed, the total vascular resistance of any organ is determined to a large extent by the resistance of the arterioles. The resistance of arterioles is, of course, largely determined by the radius of the arterioles. Therefore, blood flow through the organ is primarily regulated by a change in the internal diameter of the arterioles due to the contraction or relaxation of the muscle wall of the arterioles.

When the arterioles of an organ change their diameter, then not only the blood flow through the organ changes, but undergoes changes and a drop in blood pressure that occurs in this organ.

The narrowing of the arterioles causes a more significant drop in pressure in the arterioles, which leads to an increase in blood pressure and a simultaneous decrease in changes in the resistance of arterioles to pressure in the vessels.

(The function of the arterioles is somewhat similar to that of a dam: as a result of the closure of the dam gate, the flow decreases and its level in the reservoir behind the dam rises and the level after it decreases).

In contrast, the increase in organ blood flow caused by the expansion of arterioles is accompanied by a decrease in blood pressure and an increase in capillary pressure. Due to changes in hydrostatic pressure in the capillaries, constriction of arterioles leads to transcapillary reabsorption of fluid, while dilation of arterioles promotes transcapillary filtration of fluid.

Definition of basic concepts in intensive care

Basic concepts

Blood pressure is characterized by indicators of systolic and diastolic pressure, as well as an integral indicator: mean arterial pressure. Mean arterial pressure is calculated as the sum of one-third of pulse pressure (difference between systolic and diastolic) and diastolic pressure.

Mean arterial pressure alone does not adequately describe cardiac function. For this, the following indicators are used:

Cardiac output: The volume of blood expelled by the heart per minute.

Stroke volume: The volume of blood expelled by the heart in one contraction.

Cardiac output is equal to stroke volume times heart rate.

Cardiac Index is cardiac output corrected for patient size (body surface area). It more accurately reflects the function of the heart.

Stroke volume depends on preload, afterload and contractility.

Preload is a measure of the tension in the left ventricular wall at the end of diastole. It is difficult to quantify directly.

Central venous pressure (CVP), pulmonary artery wedge pressure (PWP), and left atrial pressure (LAP) are indirect indicators of preload. These values are referred to as “filling pressures”.

Left ventricular end-diastolic volume (LVEDV) and left ventricular end-diastolic pressure are considered more accurate indicators of preload, but they are rarely measured in clinical practice. The approximate dimensions of the left ventricle can be obtained using transthoracic or (more precisely) transesophageal ultrasound of the heart. In addition, the end-diastolic volume of the heart chambers is calculated using some methods of the study of central hemodynamics (PiCCO).

Afterload is a measure of the stress in the left ventricular wall during systole.

It is determined by the preload (which causes the ventricle to stretch) and the resistance that the heart encounters during contraction (this resistance depends on the total peripheral vascular resistance (OPSR), vascular compliance, mean arterial pressure and on the gradient in the outflow tract of the left ventricle).

OPSS, which usually reflects the degree of peripheral vasoconstriction, is often used as an indirect indicator of afterload. Determined by invasive measurement of hemodynamic parameters.

Contractile ability and compliance

Contractility is a measure of the strength of contraction of myocardial fibers at a certain pre- and afterload.

Mean arterial pressure and cardiac output are often used as indirect measures of contractility.

Compliance is a measure of the extensibility of the left ventricular wall during diastole: a strong, hypertrophied left ventricle may have low compliance.

Compliance is difficult to quantify in a clinical setting.

End-diastolic pressure in the left ventricle, which can be measured during preoperative cardiac catheterization or assessed by echoscopy, is an indirect indicator of LVEDD.

Important formulas for calculating hemodynamics

Cardiac output = SV * HR

Cardiac index = SV / PPT

Impact index = UO / PPT

Mean arterial pressure = DBP + (SBP-DBP) / 3

Total peripheral resistance = ((AVP-CVP) / SV) * 80)

Total peripheral resistance index = OPSS / PPT

Pulmonary vascular resistance = ((DLA - DZLK) / SV) * 80)

Pulmonary Vascular Resistance Index = OPSS / PPT

CV = cardiac output, 4.5-8 l / min

SV = Stroke Volume, 60-100 ml

PPT = body surface area, 2 - 2.2 m 2

SI = cardiac index, 2.0-4.4 l / min * m2

IVO = Stroke Volume Index, 33-100 ml

AVP = Mean arterial pressure, 70-100 mm Hg.

DD = Diastolic pressure, 60-80 mm Hg. Art.

SBP = Systolic pressure, 100-150 mm Hg. Art.

OPSS = total peripheral resistance, 800-1,500 dynes / s * cm 2

CVP = central venous pressure, 6-12 mm Hg. Art.

IOPSS = index of total peripheral resistance, 2000-2500 dynes / s * cm 2

SLS = pulmonary vascular resistance, SLS = 100-250 dynes / s * cm 5

PPA = pulmonary artery pressure, 20-30 mm Hg. Art.

PAW = pulmonary artery occlusion pressure, 8-14 mm Hg. Art.

ISLS = index of pulmonary vascular resistance = 225-315 dyne / s * cm 2

Oxygenation and ventilation

Oxygenation (oxygen content in arterial blood) is described by such concepts as partial pressure of oxygen in arterial blood (P a 0 2) and saturation (saturation) of hemoglobin of arterial blood with oxygen (S a 0 2).

Ventilation (movement of air into and out of the lungs) is described by the concept of minute ventilation volume and is estimated by measuring the partial pressure of carbon dioxide in arterial blood (P a C0 2).

Oxygenation, in principle, does not depend on the minute ventilation volume, unless it is very low.

IN postoperative period the main cause of hypoxia is atelectasis of the lungs. An attempt should be made to eliminate them before increasing the oxygen concentration in the inhaled air (Fi0 2).

For the treatment and prevention of atelectasis are used positive pressure at the end of expiration (PEEP) and continuous positive airway pressure (CPAP).

Oxygen consumption is estimated indirectly by the saturation of hemoglobin of mixed venous blood with oxygen (S v 0 2) and by the capture of oxygen by peripheral tissues.

The external respiration function is described by four volumes (tidal volume, inspiratory reserve volume, expiratory reserve volume and residual volume) and four containers (inspiratory capacity, functional residual capacity, vital capacity and total lung capacity): in ICU, in everyday practice, only tidal volume measurement is used ...

A decrease in functional reserve capacity due to atelectasis, supine position, lung tissue hardening (congestion) and collapse of the lungs, pleural effusion, obesity lead to hypoxia. CPAP, PEEP and physiotherapy are aimed at limiting these factors.

Total peripheral vascular resistance (OPSR). Frank's equation.

This term means total resistance of the entire vascular system the flow of blood thrown out by the heart. This relationship is described equation.

As follows from this equation, to calculate OPSS, it is necessary to determine the value of systemic arterial pressure and cardiac output.

Direct bloodless methods for measuring total peripheral resistance have not been developed, and its value is determined from Poiseuille equations for hydrodynamics:

where R is the hydraulic resistance, l is the length of the vessel, v is the viscosity of the blood, r is the radius of the vessels.

Since in the study of the vascular system of an animal or human, the radius of the vessels, their length and blood viscosity usually remain unknown, Franc... using a formal analogy between hydraulic and electrical circuits, Poiseuille equation to the following form:

Rice. 9.3. A more pronounced increase in the resistance of the vessels of the thoracic aortic basin compared with its changes in the basin of the brachiocephalic artery during the pressor reflex.

Under normal physiological conditions OPSS is from 1200 to 1700 dyne s ¦ cm. With hypertension, this value can double against the norm and be equal to 2200-3000 dyne s cm-5.