Blood pressure measurement: methods, historical facts

Blood pressure measurement is a method of determining blood pressure on the walls of blood vessels. In other words, it is the pressure coming from the heart and produced in the arteries.

The pressure in the blood vessels is not constant, but constantly changing. Among other things, the corresponding action of the heart affects blood pressure. When measuring blood pressure, two values ​​are determined (unit: millimeters of mercury or millimeters of mercury.)

The higher pressure that occurs when the heart contracts is called systolic blood pressure and the lower pressure that prevails when the heart relaxes is called diastolic blood pressure.

From a medical point of view, measuring blood pressure is especially important to find out if blood pressure values ​​are too high. Because if such high blood pressure (hypertension) persists, the heart, blood vessels, brain, eyes and kidneys can be damaged, which in extreme cases can lead to complications such as heart attack or stroke. That is why it is advisable to treat hypertension in a timely manner.

In adults, blood pressure is considered elevated if the following values ​​are obtained during measurement:

  • diastolic blood pressure over 90 mmHg.
  • systolic blood pressure over 140 mmHg. Thus, blood pressure exceeds 140 by 90.

Accordingly, the European Society of Hypertension recommends target blood pressure below 140 at 90 for almost all adults. Exceptions apply to:

  • people with diabetes with diastolic blood pressure from 80 to 85;
  • persons older than 80 years (as well as people younger than 80 years), in whom systolic blood pressure ranges from 140 to 150;
  • People with kidney and urinary protein disease who have systolic blood pressure below the 130 mark.

blood pressure levels

Since high blood pressure often goes unnoticed for a long time, it is recommended to regularly measure it. Too low blood pressure (hypotension) in itself does not have serious health consequences, but can, for example, cause fatigue and cause dizziness. The limits of low blood pressure are different for men and women:

  • In women, values ​​below 100 mmHg. Art. (Systolic) and 60 mmHg. Art. (Diastolic) indicate clear hypotension.
  • In men, doctors diagnose low blood pressure by measuring systolic values ​​below 110 mmHg. column.

Blood pressure can be determined in single measurements. However, it may also be useful to measure blood pressure over an extended period of time (for example, nocturnal hypertension or high diurnal fluctuations). Then, an 24-hour blood pressure measurement is carried out, at which repeated measurements are carried out throughout the day.

blood pressure

If you want to measure your blood pressure, you can see your doctor or pharmacy. The classic blood pressure monitor detects blood pressure on the shoulder. But you can also measure blood pressure at home - there are several electronic blood pressure devices that require a little guidance: after applying the cuff, the blood pressure monitor automatically measures your blood pressure.

For a classic measurement of blood pressure, you must have:

  • sphygmomanometer, consisting of an inflatable cuff, which is connected through a hose to a small bellows, and a manometer by which a person can read the air pressure in the cuff or blood pressure.
  • stethoscope for detecting pulse noise in the radial artery located in the elbow joint during measurement.
  • Here's how to prepare the classic blood pressure measurement process:
  • Place the cuff of the sphygmomanometer around the shoulder. The bottom edge of the cuff should end about 3 centimeter above the elbow.
  • Then palpate the radial artery in the elbow and place the stethoscope (or its external end - the so-called transducer) at this point: the stethoscope can be used to monitor the pulse during the whole process of measuring blood pressure. In order to be able to correctly measure the pressure, make sure that the stethoscope sound receiver lies correctly on the radial artery during measurement and does not slip.

Blood pressure measurement

In the next step, quickly inflate the cuff until the pulse is no longer heard, and then increase the cuff pressure even more. If the blood vessel and, accordingly, the radial artery are closed by the cuff, the blood will no longer be able to flow. As a rule, pulse sounds are not audible through a stethoscope. And only now can blood pressure be measured. To do this, the air from the cuff is gradually released using the drain plug on the sphygmomanometer, thereby reducing the pressure until the first synchronous pulses are heard. The value at which the pulse sounds are heard for the first time corresponds to systolic blood pressure.

The systolic value is the maximum blood pressure: from this value, blood pressure can slightly open the blood vessel relative to the cuff pressure during the pulse, so that blood can flow through it. However, since the diameter of the vessel is still narrowing under the pressure of the cuff, turbulent flows develop in the blood vessel. They can be heard with a stethoscope - and this allows you to measure blood pressure. The cuff pressure at this moment is approximately equal to the systolic pressure in the corresponding blood vessel, radial artery.

If the cuff pressure drops even further, blood pressure may eventually keep the vessel constantly open. Then usually there are no sounds that are possible to hear. The value at which sounds disappear approximately corresponds to diastolic blood pressure. When measuring pressure, the sphygmomanometer pressure gauge always reads a higher value first, and then a lower diastolic value.

Important information for measuring blood pressure

It is important to correctly measure blood pressure (to avoid measurement errors) and correctly interpret the results. The following notes on measuring blood pressure will help you do this more accurately:

1. Blood pressure should only be measured while lying or sitting and, if possible, in the resting phase.

2. With a shoulder circumference of a person up to 32 centimeters, a normal cuff on a sphygmomanometer is enough. It is about 13 centimeters wide and has an inflatable air tank with a length of 24 centimeters. Thicker shoulders require a slightly wider cuff to measure blood pressure. Too narrow or too wide cuff of the sphygmomanometer can lead to falsification of blood pressure values.

3. The more the sclerotic vessel is calcined, the higher the cuff pressure must be in order to compress the vessel against the increased resistance of the artery wall. Thus, the measured blood pressure values ​​are inaccurate, namely, too high.

4. After physical exertion, during pregnancy or febrile infections, blood passes through the blood vessels at a higher flow rate. The resulting turbulence is often audible even without cuff pressure. In this case, it is necessary to read the diastolic value at a time when the sounds become much quieter.

5. Systolic blood pressure can be measured by measuring blood pressure, usually up to 5 mmHg. Art., Diastolic - up to 10 mm Hg.

6. If your blood pressure is between 140 and 90, your blood pressure is too high (a sign of hypertension).

7. If blood pressure drops below the systolic value of 100 mmHg. (in women) or 110 mmHg (in men), low blood pressure (hypotension); diastolic value is usually less than 60 mm RT. pillar.

pressure measurement errors

The norm of blood pressure in children

In children, blood pressure changes with age: the measurement of blood pressure in children is usually much lower than in adolescents. In addition to age, however, gender and body size also affect blood pressure. Therefore, normal blood pressure values ​​in children are different from adults.

Recall that in adults, the optimal values ​​are about 120 mm Hg. (systolic) and 80 mm Hg. (diastolic). To normalize blood pressure and eliminate signs of hypertension, the drug is often used Recardiowhich consists of plant extracts.

Indirectly measuring blood pressure is easy - everyone can do it on their own. Unlike direct measurement of blood pressure: only a doctor can measure blood pressure directly on the spot - in different parts of the vessel and in the heart itself.

However, in order to be able to directly measure blood pressure, the doctor must insert a catheter into the artery, which has either a small sensor at the end or a pressure sensor at the external end. Accordingly, the direct measurement method is also called blood or invasive measurement of blood pressure.

When doctors measure blood pressure with a catheter, its opening is usually directed against the bloodstream. Therefore, direct measurement of blood pressure gives slightly higher values ​​than the indirect measurement method: the latter measures only static pressure - that is, pressure that acts on the walls of the vessel from the inside and keeps them open. On the other hand, in an invasive measurement of blood pressure, the catheter also measures the dynamic pressure generated by the flowing blood.

Indirect measurement of blood pressure is currently common, especially during major surgeries or as part of intensive care monitoring. Unlike the indirect Riva-Rocci procedure, direct measurement of blood pressure provides more accurate blood pressure readings.

To measure your blood pressure yourself, you do not need to do any calculations, you can read the value directly from your sphygmomanometer. But if you want to understand the principle of measuring blood pressure, you should take a look at the physical basis. So, blood flows through the arteries of a healthy person at an average rate. It is usually so low that blood flows are regulated in a blood vessel, without turbulence. To measure blood pressure, you need to artificially tighten blood flow from the outside. Because these turbulences produce an audible noise, which is used in the classical measurement of blood pressure.

When you measure your blood pressure, you simply determine the external pressure needed to swirl blood flow. An inflatable cuff for measuring pressure helps to exert pressure on the artery from the outside, for example, on the shoulder or wrist:

  • When you inflate the cuff, the artery closes from a certain external pressure - therefore, blood flow is interrupted. Due to the lack of flow, no noise is heard.
  • Now let the air exit the cuff slowly, the external pressure on the artery decreases - and the artery opens slightly again.
  • The diameter of the vessel is still narrowing, so blood cannot evenly flow through the artery - instead, turbulence is heard. While pressure from outside narrows the artery, it remains with a swirling flow.
  • If the external pressure drops below the internal pressure in the vessel (i.e. blood pressure), the artery is fully open. Then the blood flows evenly through the artery - turbulence and the noise associated with it, thus disappear.

The key physical value for creating turbulence is the Reynolds number. In the case of measuring blood pressure depending on the speed of blood flow, the width of blood vessels and blood properties (density and its viscosity). If the Reynolds number exceeds a certain value, the flow will be heard with the naked ear. You can use these sounds to measure blood pressure:

  • the appearance of sounds indicates a higher value of blood pressure;
  • the disappearance of the bottom.

The unit of pressure is Pascal (Pa). As for blood pressure, a unit of millimeters of mercury (mmHg) is preserved to this day.

History of blood pressure measurement methods

Until the 19 century, blood pressure could only be measured directly, that is, by the introduction of measuring probes into blood vessels. However, this “bloody method” was quite painful and there was also a high risk of contracting harmful bacteria.

At the end of the 19 century, the Italian pediatrician Riva-Rocci developed a completely new method for measuring blood pressure, which allowed measuring blood pressure "bloodless" from the outside. He described this method in 1896 in a journal article.

The measuring device used by Riva-Rocci consisted of a kind of bicycle tube that served as a shoulder cuff, a rubber balloon to inflate the cuff, and a mercury barometer that Riva-Rocci used to measure pressure in the armpit. When palpation of the artery on the wrist, Riva-Rocci checked during blood pressure measurement how the pulse, depending on the blood pressure, disappeared with an increase in (systolic) pressure.

how to measure blood pressure

Initially, this new method of measuring blood pressure met with rejection in medical circles, but eventually became recognized. The principle of such a measurement is still found today in modern blood pressure measuring devices, although with some technical improvements.

The scientist Riva-Rocci created a sphygmomanometer, which was the template for modern blood pressure meters.

In 1905, the Russian military doctor Korotkov improved the method developed by Riva-Rocci with a stethoscope for measuring blood pressure: a stethoscope is used to record typical noises during blood pressure measurements when blood circulates through an artery. These sounds are known as Korotkov sounds.

Since the end of the 1920's, similar devices for measuring blood pressure based on the Riva-Rocci system were found not only in hospitals, but also in medical practice.

In 1968, the fully automatic sphygmomanometer was first used as the forerunner of modern 24-watch equipment for measuring blood pressure. Since 1976, there are convenient and easy-to-use electronic self-regulating devices with which you can measure your blood pressure without the participation of a doctor. From 1989 of the year, instruments for measuring blood pressure on the index finger are available, and from 1992 of the year electronic sphygmomanometers with a cuff for the wrist are available for measuring blood pressure on the wrist.

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Lyudmila Kohanovskaya

Kakhanovskaya Lyudmila Nikolaevna, cardiologist with experience of almost 20 years. A detailed biography and information on medical qualifications are available on the authors page of our site.

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