To determine the activity of the heart, vascular system and kidneys, it is necessary to measure blood pressure. The action algorithm for determining it must be followed in order to get the most accurate numbers.
It is known from medical practice that the timely determination of pressure helped a large number of patients not to become disabled and saved the lives of many people.
History of measuring devices
The first blood pressure was measured in animals by Hales in 1728. To do this, he inserted a glass tube directly into the horse's artery. Poiseuille then added a mercury scale manometer to the glass tube, and subsequently Ludwig invented the float kymograph, which made it possible to continuously record blood pressure. These devices are equipped with mechanical stress sensors and electronic systems. Direct methods of measuring blood pressure by vascular catheterization 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 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 chambers of the heart expand and fill with blood. This is followed by systole and then diastole. The blood from the largest vessels: the aorta and pulmonary artery passes the way 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 lead to the heart.
Pressure in vessels and heart
When blood is ejected from the cavities of the heart, 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. Art., and the blood in the large veins is below atmospheric.
When blood pours out of the heart, a pulse wave is registered, which gradually fades away as it passes through all the vessels. The speed of its spread depends on the magnitude of blood pressure and the elasticity or elasticity of the vascular walls.
Blood pressure rises with age. In people from 16 to 50 years old, it is 110-130 mm Hg. Art., and after 60 years - 140 mm Hg. Art. and above.
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 this study is such that a computer is used to automate the processsignal control.
Indirect way
The technique of measuring blood pressure indirectly is possible by several methods: palpation, auscultation and oscillometric. The first method involves gradual squeezing and relaxation of the limb in the region of the artery and finger determination of its pulse below the place of compression. Rivva-Rocci at the end of the 19th century proposed the use of a 4-5 cm cuff and a mercury scale of a manometer. 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 for measuring blood pressure involves the use of this particular cuff.
The pressure in her is pumped up to the point where the pulse stops, and then slowly decreases. Systolic pressure is the moment when a pulsation appears, diastolic pressure is when the pulse attenuates or noticeably accelerates.
In 1905 N. S. Korotkov proposed a method for measuring blood pressure through auscultation. A typical device for measuring blood pressure according to the Korotkov method is a tonometer. It consists of cuff, mercury scale. The cuff is inflated with a bulb, and then the air is released gradually through a special valve.
This auscultatory method has been the standard for measuring blood pressure for more than 50 years, but surveys show that doctors rarely follow the recommendations and the technique of measuring blood pressure is violated.
The oscillometric method is used in automatic and semi-automatic devices in intensive care units, since the applicationThese devices do not require constant inflation of air into the cuff. Recording of arterial pressure is carried out at various stages of air volume decrease. Measurement of blood pressure is also possible with auscultatory dips and weak Korotkoff sounds. This method is least dependent on the elasticity of the walls of blood vessels and when they are affected by atherosclerosis. The oscillometric method made it possible to create devices for determining on various arteries of the upper and lower extremities. 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. Quality stethoscope
2. Correct cuff size.
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 to determine blood pressure, smoking and drinking alcohol- and caffeinated drinks are not recommended. The patient should sit upright, free the upper part of the arm, position it comfortably for the patient (you can put it on a table or other support), feet should be on the floor. Remove any excess clothing that may interfere with airflow into the cuff or blood flow to the arm. You and the patient should refrain from talking during the measurement. If the patient is in the supine position, it is necessary to place the upper arm at the level of the heart.
Step 3 - choose the right cuff size depending on the volume of the arm: often errors occur due to incorrecther selection. Put the cuff on the patient's arm.
Step 4 - Place the stethoscope on the same arm as you placed the cuff, feel around the elbow to find the location of the strongest impulse sounds, and position the stethoscope over the brachial artery at that location.
Step 5 - inflate the cuff: start inflating while listening to the pulse. When the pulse waves disappear, you should not hear any sounds through the phonendoscope. If the pulse is not heard, then you need to inflate so that the pressure gauge needle is on the numbers above from 20 to 40 mm Hg. Art., than at the expected pressure. If this value is unknown, inflate the cuff to 160 - 180 mmHg. st.
Step 6 - slowly deflate the cuff: deflation begins. Cardiologists recommend slowly opening the valve so that the pressure in the cuff decreases by 2 to 3 mm Hg. Art. per second, otherwise a faster decrease may result in inaccurate measurements.
Step 7 - listening to systolic pressure - the first sounds of the pulse. This is blood starting to flow through the patient's arteries.
Step 8 - Listen for a pulse. Over time, as the pressure in the cuff decreases, the sounds disappear. This will be the diastolic, or lower pressure.
Checking indicators
It is necessary to check the accuracy of the indicators. 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. As a rule, blood pressure is higher in the morning and lower in the evening. Sometimes blood pressure numbersunreliable due to the patient's concern about people in white coats. In this case, daily measurement of blood pressure is used. The algorithm of action in this case is the determination of pressure during the day.
Disadvantages of the method
At present, blood pressure is measured by auscultation in any hospital or clinic. The action algorithm has disadvantages:
• Lower SBP and higher DBP than invasive technique;
• susceptibility to noise in the room, various traffic interference;
• the need for proper placement of the stethoscope;
• Poor listening to low intensity tones;
• determination error - 7-10 units.
This blood pressure measurement technique is not suitable for monitoring during the day. To monitor the patient's condition in intensive care units, it is impossible to constantly inflate the cuff and create noise. This can negatively affect the general condition of the patient and cause his anxiety. The pressure readings will be unreliable. With the unconscious state of the patient and increased motor activity, his hand cannot be laid at the level of the heart. An intense interference signal can also be created by uncontrolled actions of the patient, so the computer will fail, which will nullify the measurement of blood pressure, pulse.
Therefore, cuffless methods are used in intensive care units, which, although inferior in accuracy, are more reliable, efficient and convenientfor constant pressure control.
How to measure blood pressure in pediatrics?
Measuring blood pressure in children is no different from the technique for determining it in adults. Only an adult cuff will not fit. In this case, a cuff is required, the width of which should be three-quarters of the distance from the elbow to the armpit. There is now a large selection of automatic and semi-automatic devices for measuring blood pressure in children.
Normal pressure figures depend on age. To calculate the systolic pressure figures, you need to multiply 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 device is a mercury tonometer, or sphygmomanometer. But digital ones are more convenient and easy to use, allowing them to be used at home.
