Для определения деятельности сердца, сосудистой system and kidneys need to measure blood pressure. The action algorithm for determining it must be followed in order to obtain the most accurate figures.
The history of the creation of measuring devices
Pressure was measured for the first time in animals by Halesin 1728. For this, he inserted the glass tube directly into the horse's artery. After this, Poiseuille added a manometer with a mercury scale to the glass tube, and later Ludwig invented a kymograph with a float, which made it possible to continuously record the blood pressure. These devices are equipped with mechanical stress sensors and electronic systems. Direct methods for measuring blood pressure by catheterization of blood vessels are used for scientific purposes in diagnostic laboratories.
How is blood pressure formed?
Rhythmic contractions of the heart include two phases:systole and diastole. The first phase, systole, is a contraction of the heart muscle, during which the heart pushes blood into the aorta and the pulmonary artery. Diastole - a period during which the cavity of the heart expands and fills with blood. Then again comes systole and later diastole. The blood of the largest vessels: the aorta and the pulmonary artery travels to the smallest - arterioles and capillaries, enriching all organs and tissues with oxygen and collecting carbon dioxide. The capillaries pass into the venules, then into the small veins and into the larger vessels, and finally into the veins that come to the heart.
Pressure in the vessels and heart
With the release of blood from the cavities of the heart pressureis 140-150 mm Hg. Art. In the aorta, it decreases to 130-140 mm Hg. Art. And the farther from the heart, the lower the pressure becomes: in venules it is 10-20 mm Hg. Art., and blood in large veins - below atmospheric.
When blood is poured from the heart, it is recordedpulse wave, which gradually dies away as it passes through all vessels. The speed of its distribution depends on the magnitude of blood pressure and the elasticity or elasticity of the vascular walls.
With age, blood pressure rises. In people from 16 to 50 years, it is 110-130 mm Hg. Art., and after 60 years - 140 mm Hg. Art. and higher.
Methods for measuring blood pressure
There are direct (invasive) and indirect methods.In the first method, a catheter with a transducer is inserted into the vessel and blood pressure is measured. The algorithm of action of this study is such that the process of signal control is carried out using a computer.
Indirect way
The technique of measuring blood pressure indirectly possibleseveral methods: palpation, auscultatory and oscilometric. The first method involves the gradual squeezing and relaxation of the limb in the area of the artery and the digital determination of its pulse below the point of compression. Rivwa-Rocci at the end of the 19th century suggested using a 4-5 cm cuff and a mercury gauge scale. However, such a narrow cuff overestimated the true data, so it was proposed to increase it to 12 cm in width. And now the technique of measuring blood pressure involves the use of this particular cuff.
The pressure in it is injected to the extent thatpulse stops, and then slowly decreases. Systolic pressure is the moment when the pulsation appears, diastolic - when the pulse dies out or accelerates noticeably.
В 1905 г. Н.С.Korotkov proposed a method for measuring blood pressure through auscultation. A typical instrument for measuring blood pressure according to the method of Korotkov is a tonometer. It consists of a cuff, mercury scale. The air in the cuff is pumped with a pear, and then gradually release the air through a special valve.
Oscillometric method is used inautomatic and semi-automatic devices in the intensive care wards, since the use of these devices does not require a constant injection of air into the cuff. Blood pressure recording is performed at various stages of air volume reduction. Measurement of blood pressure is also possible with auscultatory failures and weak Korotkov tones. This method is the least dependent on the elasticity of the walls of blood vessels and at the incidence of atherosclerosis. The oscillometric method made it possible to create instruments for detecting upper and lower extremities on various arteries. It allows you to make the process more accurate, reducing the influence of the human factor
Rules for measuring blood pressure
Step 1 - Choose the right equipment.
What you need:
1. High-quality stethoscope
2. The correct size of the cuff.
3. Aneroid barometer or automated sphygmomanometer - a device with manual inflation mode.
Step 2 - Prepare the patient:make sure he is relaxed, give him 5 minutes of rest. For half an hour, smoking and alcohol and caffeine-containing beverages are not recommended for determining blood pressure. The patient should sit upright, free the upper part of the arm, place it comfortably for the patient (can be placed on the table or other support), the feet should be on the floor. Remove excess clothing that may interfere with the inflation of air into the cuff or the flow of blood to the arm. You and the patient should refrain from talking during the measurement. If the patient is in a prone position, it is necessary to place the upper part of the arm at the level of the heart.
Step 3 - choose the right size of the cuff depending on the volume of the arm: often mistakes are due to incorrect selection. Put the cuff on the patient's arm.
Step 4 - place the phonendoscope on the same hand,where you placed the cuff, feel the arm on the elbow to find the place of the most powerful impulse sounds, and place the stethoscope over the brachial artery in this place.
Шаг 5 – раздуть манжету:start pumping up while listening to the pulse. When the pulse waves disappear, you should not hear any sounds through the stethoscope. If the pulse is not audible, then you need to inflate so that the gauge needle is in numbers higher than 20 to 40 mm Hg. Art. than at the expected pressure. If this value is unknown, inflate the cuff to 160 - 180 mm Hg. Art.
Step 6 - slowly blow off the cuff:deflation begins. Cardiologists recommend slowly opening the valve so that the pressure in the cuff is reduced by 2 - 3 mm Hg. Art. per second, otherwise a faster decline may lead to inaccurate measurements.
Step 7 - listening to systolic pressure - the first pulse sounds. This blood begins to flow through the patient’s arteries.
Step 8 - Listen to the pulse. Over time, when the pressure in the cuff decreases, the sounds disappear. This will be the diastolic, or lower pressure.
Performance check
Необходимо проверить точность показателей.To do this, measure the pressure on both hands to average the data. To check the pressure again for accuracy, you should wait about five minutes between measurements. Blood pressure is usually higher in the morning and lower in the evening. Sometimes the blood pressure figures are unreliable due to patient anxiety about people in white coats. In this case, use the daily measurement of blood pressure. The action algorithm for this is to determine the pressure during the day.
Disadvantages of the method
Currently, an auscultatory method is used to measure blood pressure in any hospital or clinic. The action algorithm has disadvantages:
• lower SAD numbers and higher DBP figures than those obtained with an invasive technique;
• susceptibility to noise in the room, various traffic disturbances;
• the need for proper positioning of the stethoscope;
• poor listening of low-intensity tones;
• determination error - 7-10 units.
This blood pressure measurement techniqueunsuitable for monitoring procedure during the day. To monitor the patient’s condition in the intensive care wards, it is impossible to constantly pump up the cuff and create noise. This can adversely affect the general condition of the patient and cause his anxiety. Pressure numerals will be unreliable. In the unconscious state of the patient and increased motor activity his hand cannot be laid at the heart level. An intense signal of interference can also create uncontrolled actions of the patient, so the computer will crash, which will negate the measurement of blood pressure, pulse.
Therefore, in the reanimation wards, moneyless methods are used, which, although inferior in accuracy, are more reliable, fast and convenient for constant pressure control.
How to measure blood pressure in pediatrics?
Measurement of blood pressure in children does not differ from technologydefine it in adults. Only an adult cuff will not work. In this case, a cuff is required, the width of which should be three-quarters of the distance from the elbow bend to the axillary fossa. Currently, there is a large selection of automatic and semi-automatic instruments for measuring blood pressure in children.
Numbers of normal pressure depend on age.To calculate the numbers of systolic pressure, you need to multiply the number of the child's age in years by 2 and increase by 80, the diastolic is 1/2 - 2/3 of the previous figure.
Blood Pressure Monitors
Blood pressure meters are also called tonometers.There are mechanical and digital tonometers. Mechanical are mercury and aneroid. Digital - automatic and semi-automatic. The most accurate and long-term instrument is a mercury tonometer, or sphygmomanometer. But digital is more convenient and easy to use, which allows them to be used at home.
