Blood pressure measurement: methods, historical facts

Blood pressure measurement is a method of measuring the pressure of blood against the walls of blood vessels. In other words, it is the pressure emanating 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 suffering 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 measure it regularly. Too low blood pressure (hypotension) does not in itself have serious health consequences, but can, for example, cause fatigue and dizziness. Low blood pressure limits 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 have your blood pressure measured, you can contact your doctor or pharmacy. The classic blood pressure monitor measures the blood pressure at the shoulder. But you can also measure your blood pressure at home - there are several electronic blood pressure devices that require a little guidance: after the cuff is applied, the blood pressure monitor automatically measures the 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 at the elbow and place the stethoscope (or its outer end - the so-called transducer) at this point: the stethoscope can be used to monitor the pulse during the entire blood pressure measurement process. To be able to correctly measure the pressure, make sure that the stethoscope sound receiver is correctly placed on the radial artery during measurement and does not slip.

Blood pressure measurement

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

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

If the cuff pressure drops further, blood pressure may end up keeping the vessel open permanently. Then there are usually no sounds that can be heard. The value at which the sounds disappear roughly corresponds to diastolic blood pressure. When measuring pressure, the sphygmomanometer manometer 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 Cardiline which consists of plant extracts.

It is easy to indirectly measure blood pressure - anyone can do it on their own. In contrast to 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, the opening is usually against the bloodstream. Therefore, direct measurement of blood pressure gives slightly higher values ​​than the method of indirect measurement: the latter measures only static pressure - that is, the pressure that acts on the walls of the vessel from the inside and keeps them open. On the other hand, in invasive blood pressure measurement, 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 off from a certain external pressure - so blood flow is interrupted. No noise is heard due to lack of flow.
  • Now let the air out of 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 flow evenly through the artery - instead, turbulence is heard. As long as external pressure constricts the artery, it remains in a swirling flow.
  • If the external pressure drops below the internal pressure in the vessel (i.e., blood pressure), the artery is completely open. Then the blood flows evenly through the artery - turbulence and associated noise, 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 19th century, blood pressure could only be measured directly, that is, by inserting measuring probes into the blood vessels. However, this “bloody method” was quite painful and there was also a high risk of contamination with 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, a fully automatic sphygmomanometer was used for the first time as the forerunner of the modern 24-hour blood pressure measurement equipment. Since 1976, there have been convenient and easy-to-use electronic self-regulating devices with which you can measure your blood pressure without the participation of a doctor. Since 1989, index finger blood pressure monitors have been available, and since 1992 electronic sphygmomanometers with wrist cuffs have been available for measuring blood pressure at the wrist.

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Lyudmila Kohanovskaya

Kakhanovskaya Lyudmila Nikolaevna, a cardiologist with nearly 20 years of experience. A detailed biography and information about medical qualifications are posted on the authors page of our website.