Measurement of AD - the algorithm of action. Arterial pressure

To determine the activity of the heart, vascular system and kidneys, it is necessary to perform blood pressure measurement. The algorithm of action for its determination must be observed in order to obtain the most accurate figures. It is known from medical practice that the timely determination of pressure has helped a large number of patients not become invalids and saved the lives of many people.

History of creation of measuring devices

For the first time, pressure was measured in animals by Hales in 1728. To do this, he inserted a glass tube directly into the artery of the horse. After that, Poiseuil 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 blood pressure. These machines are equipped with mechanical stress sensors and electronic systems. Direct methods for measuring BP by vascular catheterization are used for scientific purposes in diagnostic laboratories.

How is the blood pressure formed?

Rhythmic contractions of the heart include two phases: systoles and diastoles. The first phase - systole - is the contraction of the heart muscle, during which the heart pushes blood into the aorta and pulmonary artery. Diastole is the period during which the heart cavities widen and fill with blood. Then the systole again comes and in the subsequent diastole. Blood from the largest vessels: the aorta and the pulmonary artery passes the path to the smallest - arterioles and capillaries, enriching all organs and tissues with oxygen and collecting carbon dioxide. Capillaries pass into venules, then into small veins and into larger vessels, and finally into veins that approach the heart.

Pressure in the vessels and heart

When discharging blood from the heart cavities, the pressure is 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 the venules it is 10-20 mm Hg. St., And blood in large veins - below atmospheric.

When blood flows from the heart, a pulse wave is registered, which gradually fades as it passes through all the vessels. The rate of its spread depends on the magnitude of arterial 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. St., 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 the blood pressure is measured. The algorithm of the action of this study is such that the computer controls the signal control process.

Indirect way

The technique of measuring blood pressure by an indirect method is possible by several methods: palpatory, auscultatory and oscillometric. The first method involves the gradual squeezing and relaxation of the limb in the artery and finger determination of its pulse below the compression site. Riva-Rocchi in the late 19th century suggested using a cuff of 4-5 cm and a mercury scale of a manometer. However, such a narrow cuff overstated the true data, so it was suggested 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 pumped to the point where the pulse stops, and then slowly decreases. Systolic pressure is the moment when pulsation occurs, diastolic pressure - when the pulse decays or appreciably accelerates.

In 1905 N.S. Korotkov proposed a method of measuring blood pressure by auscultation. A typical device for measuring blood pressure by the Korotkov method is a tonometer. It consists of a cuff, a mercury scale. The air in the cuff is pumped with a pear, and then gradually air is released through a special valve.

This auscultatory method is the standard for measuring blood pressure for more than 50 years, but according to surveys, doctors rarely follow recommendations, and the technique of measuring blood pressure is disturbed.

The oscillometric method is used in automatic and semiautomatic devices in intensive care wards, since the use of these devices does not require constant air pumping into the cuff. The recording of blood pressure is carried out at various stages of reducing the air volume. Measurement of blood pressure is also possible with auscultatory failures and weak tones of Korotkov. This method is least dependent on the elasticity of the walls of the vessels and when they are affected by atherosclerosis. The oscillometric method made it possible to create instruments for determining the upper and lower extremities on various arteries. It allows 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. Qualitative stethoscope

2. Correct cuff size.

3. Barometer-aneroid or sphygmomanometer automated - the device with a manual mode of inflation.

Step 2 - prepare the patient: make sure that he is relaxed, give him 5 minutes of rest. For half an hour to determine blood pressure is not recommended smoking and drinking alcohol and caffeinated drinks. The patient should sit upright, release the upper part of the arm, arrange it comfortably for the patient (you can put it on a table or other support), feet should stand on the floor. Remove excess clothing that may interfere with air pumping into the cuff or blood flow to the hand. You and the patient should refrain from talking during the measurement. If the patient is lying down, it is necessary to place the upper part of the hand at the level of the heart.

Step 3 - choose the right cuff size, depending on the volume of the hand: often mistakes arise due to improper selection. Put the cuff on the patient's arm.

Step 4 - place the phonendoscope on the same arm where you placed the cuff, feel your hand on the elbow bend to find the location of the strongest pulse sounds, and place the stethoscope over the brachial artery in this place.

Step 5 - inflate the cuff: start pumping, while listening to the pulse. When pulse waves disappear, you should not hear any sounds through the phonendoscope. If the pulse is not audible, then you need to inflate so that the needle of the pressure gauge is on the numbers higher from 20 to 40 mm Hg. Than at the presumed 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 to 3 mm Hg. Art. Per second, otherwise a faster reduction can lead to inaccurate measurements.

Step 7 - listening to systolic pressure - the first sounds of the pulse. 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 diastolic, or lower pressure.

Verification of indicators

It is necessary to check the accuracy of indicators. To do this, measure the pressure on both hands to average the data. To check the pressure again for accuracy, wait about five minutes between the measurements. Typically, blood pressure is higher in the morning and lower in the evening. Sometimes blood pressure figures are unreliable because of the patient's concern about people in white coats. In this case, a 24-hour BP measurement is used. The algorithm of action in this case is the determination of pressure during the day.

Disadvantages of the method

At present, the auscultatory method in any hospital or clinic is the measurement of blood pressure. The algorithm of action has disadvantages:

• lower figures of SBP and higher DBP figures than those obtained with an invasive procedure;

• susceptibility to room noise, various traffic disturbances;

• the need for the correct location of the stethoscope;

• poor tones of low intensity;

• the error of determination is 7-10 units.

This technique of measuring blood pressure is unsuitable for monitoring procedures during the day. To monitor the patient in the intensive care unit, it is not possible to constantly inflate the cuff and create noise. This can negatively affect the general condition of the patient and cause his anxiety. The pressure codes will be unreliable. With unconsciousness of the patient and increased motor activity, his hand can not be laid at the level of the heart. An intense signal of interference can create and uncontrolled actions of the patient, so the computer will malfunction, which will bring to nothing the measurement of blood pressure, pulse.

Therefore, in the intensive care unit, no-mange methods are used, although they are inferior in accuracy, but they are more reliable, operative and convenient for constant monitoring of pressure.

How to measure BP in pediatrics?

Measurement of blood pressure in children does not differ from the technique of determining 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 to the axillary fossa. Currently, there is a large selection of automatic and semi-automatic devices for measuring blood pressure in children.

The figures of normal pressure depend on the age. To calculate the figures for systolic pressure, you need to multiply the figure of the child's age in years by 2 and increase by 80, the diastolic ratio is 1/2 - 2/3 of the previous figure.

Devices for measurement of arterial pressure

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 a sphygmomanometer. But digital is more convenient and easy to operate, which allows them to be used at home.