Blood pressure, or blood pressure is an important indicator of the state and functioning of the human body. What does it mean physically? This is the force of the vertical pressure of blood on the walls of blood vessels. The measurement of this indicator is the first procedure at a doctor's appointment. Its level is expressed in numbers in fractions: the top line is systolic, the bottom line is diastolic pressure.
How does it happen?
When the heart contracts, systoles (ventricular contraction) and diastole (relaxation) occur rhythmically. Let's consider in more detail. When the heart contracts, it pushes blood from the left ventricle into the aorta, and this force creates pressure on the walls of the vessels. What affects the values of this indicator?
Changes in arterial blood pressure are affected by:
- the amount and viscosity of blood that is ejected into the circulation per unit time;
- the capacity of the vascular bed itself;
- heart rate (HR);
- resistance of vessel walls;
- timedays;
- tension of arterial walls;
- physical activity;
- external environment, etc.
Methods for measuring variable pressure are discussed in this article. Let's continue our study.
When blood is ejected from the heart into the aorta, systolic pressure (BP) occurs. The aortic valves then close. The stomachs relax. The pressure drops. Now it is diastolic (DD). The difference between them is the pulse pressure.
The unit of measurement of blood pressure is considered to be 1 mmHg. Norm SD - 110-129 mm Hg. Art., DD - 70-99 mm Hg. Art. Numbers other than these should be considered pathological.
Difference is the process of pressure change (fall or jump). It occurs during a certain time, for example, in the morning and in the evening. Methods for measuring pressure drops are no different from conventional blood pressure measurements. Next, consider devices designed for these purposes.
Features
Anatomical and physiological structure of the cardiovascular system involves the following types of pressure:
- in the cavity of the heart;
- by vessels - arterial, venous and capillary.
Let's take a closer look. The peculiarity of the circulatory system is that the pressure in it increases from the center to the periphery. This was established by measuring the variable pressure difference method. That is, with a decrease in the radius of the vessel, the indicator drops, because the hydraulic resistance of the blood increases.
Only the aorta can boast the highest pressure. Furtherit decreases immediately by 15%, and in the capillaries - already by 85%. It turns out that the heart spends most of its energy on overcoming precisely this pressure in small vessels. The lowest value of the indicator was obtained in the vena cava system. The movement of blood through the vessels occurs due to the pressure gradient, i.e. its difference in different areas.
Why know your BP
Knowing this information is necessary because even small pressure deviations from the norm create the prerequisites for serious diseases and pathological conditions - heart attacks, strokes, heart and kidney failure.
It is blood pressure that should be measured first of all in case of complaints of dizziness, headaches and weakness. An increase always begins with vascular damage. It has long been known that it was the measurement of pressure that many times in the practice of doctors saved the lives of patients. Doctors in antiquity knew about the value of this indicator. Therefore, they treated many diseases with bloodletting and noted an improvement in the condition of many patients.
How measuring devices appeared
The history of blood pressure monitors began 300 years ago. For the first time, blood pressure was measured in animals by Stephen Hels in 1733. To do this, he inserted a glass tube directly into the horse's artery and determined the indicator by the height of the blood column in it.
Poiseuille improved this primitive apparatus by adding a manometer with a mercury scale to the existing device. Subsequently, Ludwig invented the float kymograph, which made it possible to continuouslywrite down the desired values.
At the end of the 19th century, the Italian Riva-Rocci created a bloodless method for measuring blood pressure by palpation. He suggested using a special rubber cuff for this to pinch the artery on the arm.
In 1905, the Russian doctor N. S. Korotkov improved the method. Its peculiarity was to listen with a stethoscope to the tones of the artery in the elbow bend. Today, this principle of work on the compression of blood vessels in order to measure blood pressure is still used today.
Types of blood pressure monitors
All devices are divided into mechanical and electronic. Their operation is a method of measuring variable differential pressure. You can do this at any time of the day. Electronic devices exist automatic and semi-automatic, the principle of operation is the same for all. They are used for home measurements. Automatic blood pressure monitors are divided into shoulder and wrist devices.
Mechanical devices
They, for the most part, consist of these parts:
- compression cuff;
- mercury or spring pressure gauge;
- pear-supercharger (cylinder);
- vent valve.
All these parts are connected by rubber tubes. This system comes with a phonendoscope. Such devices are used mainly in medical institutions.
Semi-automatic devices
The difference from a mechanical tonometer is the presence of a bulb that pumps air into the cuff. The readings are taken throughbuilt-in electronics, they are shown on the display screen. These devices are used both in hospitals and at home.
Automatic electronic shoulder gauges
They work very simply. The patient needs to put the cuff on his shoulder and press the start button. Everything else is up to the automation of the device: cuff inflation, analysis and result. These meters are convenient for use at home.
Automatic wrist blood pressure monitors
They differ from other devices only in their location on the body during manipulation. They are convenient to take with you on the road due to their compactness. But such a measurement of blood pressure is not recommended for those who have changes in the vessels (with atherosclerosis, diabetes mellitus).
There are models that record the time and date of timing, errors during operation. The data is stored in the instrument's memory and can be displayed on a computer monitor. This is used for daily monitoring of blood pressure in a certain category of patients.
Next, consider methods for measuring blood pressure.
Non-invasive (indirect) methods
Most of these methods are compression methods and are based on the alignment of blood pressure with external (atmospheric) pressure when air is released from the cuff.
They are divided into:
- Palpatory - the easiest. Riva Rocci proposed. The pressure in the cuff is raised by pumping air into it. And obviously high, to pinch the artery. The cuff is then slowly deflatedletting the air out of her. At the same time, the appearance of a pulse on the wrist in the radial artery is monitored. The pressure value will be systolic.
- Auscultatory - used since 1905. The Korotkov method for measuring blood pressure is currently recognized by WHO as the standard for non-invasive blood pressure measurement. Although the data when using it are somewhat lower for DM and higher for DD than when measuring invasively. The manometer can be mercury, pointer or electronic. The cuff is always applied in the area of the brachial artery, located at the level of the heart, and its pressure matches the pressure in the aorta.
- Oscillometric - will be discussed in detail later in the article.
Features of the auscultatory method
The patient's hands should be located at the level of the heart, on the table, and he himself should sit. Auscultation is performed with a phonendoscope over the projection of the brachial artery in the cubital fossa. The physical basis of the clinical method of measuring blood pressure lies in the fact that there is a phenomenon of "sounding" of the artery. Explain.
The passage of blood through the squeezed area creates noise due to the turbulent flow of blood. Their appearance is an indicator of SD. These are the first tones. Air continues to be released and blood flow gradually becomes fully laminar. Whirlwind noises disappear. This means that the external pressure has become equal to the arterial pressure. The cessation of noise will show on the pressure gauge DD.
This is the physical basis of the blood pressure measurement method. Classical blood pressure in an adult: SD - 128-132, DD - 83-85 mm Hg. Art. on the right and left hand respectively.
Although the Korotkoff blood pressure measurement is officially the standard, it has its pros and cons. Plus, it is highly resistant to hand movement.
More cons:
- room noise changes performance;
- the head of the phonendoscope must be positioned correctly - in the cubital fossa;
- need to have measurement skills.
In addition, errors may occur if the size of the cuff and the volume of the arm do not match, the position of the arm is incorrect, the rapid release of air from the cuff.
Direct method
Invasive (direct) method of measuring blood pressure is applied by catheterization of blood vessels. Used for scientific purposes in diagnostic laboratories, cardiology and cardiac surgery centers.
Today, this method is the only method for measuring pressure in the aorta and the heart itself. A needle is connected to the pressure gauge in the arteries or a cannula through a tube. Or the sensor itself is inserted into the bloodstream. Its signals in the form of a curve are recorded by the magnetic tape of the manometer.
The method is applicable only in a hospital, in complete sterility, when there is a need for daily monitoring. The pressure and measurement time is drawn as a curve.
Although these methods of measuring blood pressure are highly accurate, they are quite traumatic, since the needle is inserted directly into the vessel or cavity of the heart.
The disadvantage of the method is that such patients need the constant presence of a doctor because of the risk of probe disconnection with subsequent bleeding, thrombosis inpuncture site, secondary infection.
Invasive pressure measurement - a direct way to assess performance. It requires sufficient blood flow in the artery.
The disadvantage of direct methods for measuring blood pressure is the need to penetrate the vessel cavity, which is always fraught with complications.
Oscillometric method (electronic)
The method is based on the registration of pressure pulsations that occur in the device when blood passes through the squeezed section of the artery. Devices of this type are most suitable for home use. The advantage of the method is that no assistant is needed.
Skills for taking measurements are also not needed, the device is resistant to noise in the room. There is an opportunity not to bare your hand - with a thin jacket, accuracy will not be disturbed. But practitioners consider the mechanical method to be more accurate, since the performance of electronics depends on its quality, which is not always due to the high price.
With the help of an oscilloscope, the frequency of blood pulse oscillations is recorded and displayed on the tonometer display. The principle of operation is the same - compression, just the sensors are located in the cuff itself. Inflation and deflation is automatic.
Cons:
- High price.
- Dependence of devices on batteries. If they start to discharge, there will be no accuracy.
- Must be still while measuring.
Why doesn't BP match on the left and righthands
This is due to the difference in the structure of blood vessels. The left subclavian artery departs independently from the aorta and immediately joins the left brachial circulation, where blood pressure is measured.
On the right, the course of the vessels is different. From the aorta, the brachiocephalic trunk first departs, which then divides into the carotid and subclavian arteries. Therefore, blood pressure on the right arm is usually 5-10 mm Hg. Art. lower than on the left limb (measurements are preferably carried out on it).
Pressure and age
With age, blood pressure rises evenly in men. But in women, before the onset of menopause, this process occurs weakly, since the body is under the protection of estrogens. But after that (with the fading of the ovaries), the weaker sex not only catches up, but also overtakes men in terms of increasing blood pressure.
What can affect the pressure when measuring
Overweight people and smokers always score higher. Blood pressure rises during stress and physical exertion, with constipation and after eating, after drinking alcohol, tea and coffee, before urinating, when in a cold room, if there is a mobile phone nearby, in athletes before the start, after taking a bath or shower.
Basic rules for the procedure - how to measure:
- at rest;
- after eating an hour;
- after urinating.
Five deep breaths can be taken to stabilize the pressure.
Measuring order in the elderly and pregnant
In older people more oftenthere is instability of blood pressure due to changes in blood vessels. Measurements are carried out three times and the arithmetic mean is taken. In addition, in older people, pressure can be affected by a change in posture, so the indicators are taken while standing and sitting.
By blood pressure you can judge the course of pregnancy. When measuring pressure, a woman in position should be reclining.
