Blood pressure

  • Blood pressure in various diseases
  • Blood pressure in children
  • Blood pressure is the pressure inside the blood vesselsinside of the arteries (blood pressure), capillaries (capillary pressure) and veins (venous pressure).
    Blood pressure depends on the strength of heart contractions, the elasticity of arteries and mainly resistance, which have a flow of peripheral blood vessels (arterioles and capillaries. To a certain extent blood pressure depends on the properties of blood - viscosity determining the internal resistance and the number of her body.
    During contraction (systole) of the left ventricle into the aorta is thrown around 70 ml of blood; the amount of blood cannot pass through the capillaries, and so elastic the aorta several stretches, and blood pressure increased (systolic pressure). During diastole, when aortic heart valve is closed, the wall of the aorta and large vessels, dwindling under their own elasticity, push the excess in these vessels, the blood in the capillaries; pressure gradually decreases and by the end of diastole reaches its minimum value (diastolic pressure). The difference between systolic and diastolic pressure is called the pulse pressure.
    Capillary pressure depends on the pressure of blood in the arterioles, the number of currently active capillary permeability of the wall.
    The value of venous pressure depends on the tone of venous vessels and blood pressure in the right atrium. As the distance from the heart, blood pressure drops. For example, in the aortic blood pressure 140/90 mm RT. century (the first number is the systolic pressure, the second - diastolic), in large blood vessels - 110/70 mm RT. senior capillary blood pressure is reduced from 40 mm RT. senior 10-15 mm RT. century In the upper and lower hollow vein and large veins of the neck pressure can be negative.
    Regulation of blood pressure. Blood pressure ensures the promotion of blood through the capillaries of the body, the implementation of exchange processes between the capillaries and intercellular fluid and eventually normal course of metabolic processes in tissues.
    The constancy of blood pressure is maintained on the principle of self-regulation. According to this principle, any deviation some vital functions from the norm is an incentive to return it to its normal level.
    Any deviation blood pressure increase or decrease causes excitation special baroretseptorov, located in the walls of blood vessels. Particularly high concentration of them in the arch of the aorta, carotid sinus, the vessels of the heart, brain, etc., of stimulation of receptors on afferent nerve fibers come to vasomotor center located in the medulla, and changing his tone. Hence the pulses are sent to the blood vessels, by changing the tone of the vascular wall and, thus, the value of the peripheral resistance to blood flow. Time changes and activity of the heart. Because of these divergent influences blood pressure returns to normal levels.
    In addition, sosudodwigatelny centre is influenced by a particular substance produced in different organs (so-called humoral effect). Thus, the level tonic excitation vasomotor center is determined by the interaction him two types of effects: neural and humoral. Some of influence leading to increased tone and increase blood pressure - the so-called Pressor effects; others reduce the tone of vasomotor center and have thus depressant effect.
    Humoral regulation of blood pressure levels is peripheral vessels through action on the blood vessels of specific substances (adrenaline, noradrenaline, and others).
    Methods of measurement and registration of blood pressure. There are direct and indirect methods of measuring blood pressure. The direct method in clinical practice to use for measurement of venous pressure (see Phlebotomine). In healthy people venous pressure 80-120 mm waters. article.. Most common method of indirect blood pressure measurement is the auscultatory method Korotkov (see Sphygmomanometry). During the examination the patient sits or lies. Hand aside flexor surface facing up. The unit is mounted so that the artery, which measure blood pressure, and the device was at the level of the heart. In a rubber cuff, worn on the shoulder of the subject and off-gauge pump air. At the same time using a stethoscope to listen to an artery below the overlay cuff (usually in the cubital fossa). The air should be pumped up full of compression of the lumen of the artery, which corresponds to the termination hearing the tones on arteries. Then from the cuffs slowly let the air out and watching the readings of manometer. As soon as systolic arterial pressure exceeds the pressure in the cuff, with the power of the blood passes through a strangled portion of the vessel, and easy listening to the noise of the moving blood. This point is marked on the manometer scale and consider as an indicator of systolic blood pressure. With the further release of air from the cuffs obstruction to blood flow is becoming less noise gradually weaken and finally disappear. The gauge at this point, consider the size of diastolic blood pressure.
    Normal blood pressure in the brachial artery person aged 20-40 years is on average 120/70 mm RT. Art. With age, blood pressure, especially systolic, raised due to the decrease in the elasticity of the walls of large arteries. For rough estimates of height blood pressure depending on the age, you can use the formula:
    Admax.= 100+, where Admax-systolic pressure in millimeters of mercury), In the age studied in years.
    Systolic pressure in physiological conditions ranges from 100 to 140 mm RT. Art., diastolic pressure - from 60 to 90 mm RT. senior Systolic pressure of 140 to 160 mm RT. senior considered hazardous in relation to the possibilities of development of hypertension.
    For registration blood pressure applied oscillography (see).