What is a Blood Pressure Monitor?

A sphygmomanometer is an instrument for measuring blood pressure, also called a blood pressure meter. Sphygmomanometers mainly include auscultation sphygmomanometer and oscillometric sphygmomanometer.

Auscultatory sphygmomanometers mainly include: mercury sphygmomanometer (pressure gauge), spring table type sphygmomanometer (calender sphygmomanometer, light-display sphygmomanometer, LCD sphygmomanometer, etc.).

The oscillometric method is also called the oscillating method. Its principle is to obtain the oscillating wave generated during the deflation process and convert the blood pressure value through a certain algorithm conversion. Most electronic sphygmomanometers are designed using the oscillometric principle.

Chinese name: sphygmomanometer
Foreign name: sphygmomanometer

Management category: Class II medical devices
Category Name: sphygmomanometer

Sphygmomanometer

Systemic arterial blood pressure is referred to as blood pressure (BP). Blood pressure is the pressure that acts on the wall of a blood vessel when it is flowing in a blood vessel, and it is the motive force that promotes blood flow in the vessel. The ventricle contracts, and blood flows from the ventricle into the artery. At this time, the pressure of the blood on the artery is the highest, which is called systolic blood pressure (SBP). Ventricular diastole, arterial vasoconstriction, blood continues to slowly move forward, but blood pressure drops, and the pressure at this time is called diastolic blood pressure (DBP)

Sphygmomanometer development history

In 1628, British scientist William Harvey noticed that when arteries were cut, blood spewed out as if driven by pressure. By touching the pulse of the pulse, blood pressure is felt.

In 1835, Julius Elisson invented a sphygmomanometer that transmitted the pulse of the pulse to a narrow column of mercury. When the pulse pulsed, the mercury would beat up and down accordingly. For the first time, the doctor could Pulse and blood pressure are measured with open arteries. But because of its inconvenience to use, its rough fabrication, and its inaccurate readings, other scientists have improved it. A sphygmomanometer measures blood pressure based on the height of a mercury column, and a barometer measures air pressure in the same way.

In 1860, French scientist Etienne Jour Mare developed the best sphygmomanometer at the time, which amplifies the pulse of the pulse and records the trajectory of the pulse on a roll of paper. This sphygmomanometer can also be carried around, and Mare used this sphygmomanometer to study the abnormal beating of the heart.

The sphygmomanometer used by doctors was invented in 1896 by Italian scientist Hipioni Rivalucci. It has an inflatable cuff to block the flow of blood. The doctor uses a stethoscope to listen to the pulse of the pulse, and at the same time reads the blood pressure on a scale ^[1] .

How the sphygmomanometer works

The main principle of a sphygmomanometer refers to the process of measuring blood flow pressure during this period by applying pressure to the local arteries to prevent the pulse of the local arteries by applying pressure. The measuring principle of sphygmomanometer can be divided into auscultation method and oscillometric method.

Auscultation is also called Coriolis, which is also divided into artificial Coriolis and electronic Coriolis. The artificial Coriolis method is also a method commonly used by doctors and nurses to measure blood pressure with pressure gauges and stethoscopes; the electronic Coriolis method uses electronic technology to replace doctors and nurses' methods of measuring the Coriolis sound ^[1] . The principle is that the cuff is tied to the upper arm and its pressure acts on the brachial artery. Adjust the cuff gas to change the pressure, and listen to the pulsating sound with a stethoscope to obtain systolic and diastolic blood pressure ^[1] .
The oscillometric method, also called the oscillating method, is a relatively advanced electronic measurement method developed in the 1990s. Its principle is to automatically adjust the inflation of the cuff bound to the upper arm and change the pressure. The oscillating wave received by the pressure sensor is gradually deflated. According to the change of the oscillating wave, the pressure and fluctuation detected by the pressure sensor also change accordingly. The moment with the greatest fluctuation is selected as the reference point. Based on this point, look forward The fluctuation point of a certain value is the systolic pressure, and the fluctuation point of a certain value is searched backward as the diastolic pressure. This value is set differently by different manufacturers.

Sphygmomanometer related data

Reference value of Chinese average normal blood pressure (mmHg)

age	Systolic blood pressure (male)	Diastolic blood pressure (male)	Systolic blood pressure (female)	Diastolic blood pressure (female)
16-20	115	73	110	70
21-25	115	73	110	71
26-30	115	75	112	73
31-35	117	76	11 4	74
36-40	120	80	116	77
41-45	124	81	122	78
46-50	128	82	128	79
51-55	134	84	134	80
56-60	137	84	139	82
61-65	148	86	145	83

Classification and basic structure of blood pressure monitor

Mercury sphygmomanometer. There are two types: desktop and vertical. The structure of the desktop mercury sphygmomanometer is reasonable, solid and reliable. The height of the sphygmomanometer can be adjusted arbitrarily. It is the most commonly used because of its reliable results. However, the latter is slightly larger and not portable, and there is a risk of mercury leakage ^[3] . The principle of measuring blood pressure is auscultation, which consists of a balloon, a cuff and a manometer. The two tubes of the rubber cuff of the cuff are connected to the balloon and the manometer respectively, and the three form a closed pipeline system. There are two types of pressure gauges: mercury cylinder type and spring type ^[1] .
Blood Pressure Monitor. It can be subdivided into upper arm type, wrist type, finger type, manual type, automatic type and so on according to the measurement part. Its advantages are easy operation and intuitive reading. It only needs to turn on the switch to measure automatically, which is suitable for home use. However, the electronic sphygmomanometer also has the disadvantage of large errors. It also needs to be calibrated according to the standard mercury column sphygmomanometer. The principle is auscultation method (also known as Coriolis method) or oscillometric method (also known as oscillation method. It is mainly composed of gas pressure sensor, pressurized miniature air pump, electronically controlled exhaust valve, related software, mechanical slow exhaust valve and Solenoid quick exhaust valve and other components ^[1] .
Barometer sphygmomanometer. Clinically it is also called aneroid sphygmomanometer, spring type sphygmomanometer. The pressure measurement is performed by using a pneumatic pump, which is small in size and convenient to carry. However, as the number of applications increases, the accuracy of the results will be affected due to changes in the properties of the spring. Therefore, regular calibration with a standard mercury column sphygmomanometer is required. Very rarely used ^[3] .

How to use sphygmomanometer

Electronic sphygmomanometer

1) Keep the room quiet, and the room temperature should be kept at about 20 .

2) Before the measurement, the subject should be relaxed. It is best to rest for 20-30 minutes, empty the bladder, not drink alcohol, coffee and strong tea, and stop smoking.

3) The test subject can take a sitting or supine position. The arm to be tested should be placed at the same level as the right atrium (the arm should be at the same level as the fourth rib cartilage when sitting, and the armpit midline when lying), and 45 degrees outreach. Roll up the sleeves to the armpit, or take off one sleeve for easy measurement.

4) Before measuring the blood pressure, the air in the cuff of the sphygmomanometer should be evacuated, and then the cuff should be tied to the upper arm flatly. It should not be too loose or too tight, so as not to affect the accuracy of the measured value. The brachial artery in the middle of the airbag facing the elbow socket (most electronic sphygmomanometers are marked with arrows on the cuff), the lower edge of the cuff is 2 to 3 cm from the elbow socket.

5) Turn on the electronic sphygmomanometer and record the blood pressure measurement result after the measurement is completed.

6) Completely deflate after the first measurement, wait at least 1 minute, repeat the measurement once, and take the average value of 2 times to obtain the blood pressure value. In addition, if you want to determine whether you have high blood pressure, it is best to take measurements at different times. It is generally believed that at least three blood pressure measurements at different times can be used to determine high blood pressure.

7) If you need to observe blood pressure changes every day, you should use the same position and the same blood pressure meter to measure the blood pressure of the same arm at the same time, so that the measured results will be more reliable.

Mercury sphygmomanometer

1) Observe that the zero position should be 0.5kPa (4mmHg) when not pressurized before use; after pressurization, after 2min without deflation, the mercury column should not fall more than 0.5kPa within 1min. It is forbidden to break the column when pressurized. Or bubbles appear, it will be more obvious under high pressure.

2) Use a balloon to inflate the cuff bound to the upper arm.

3) When the applied pressure is higher than the systolic pressure, the balloon is slowly deflated outward, so that during the measurement process, the rate of deflation is controlled according to the patient's pulse beat rate. Those with slow heart rate should try to slow down.

4) The stethoscope begins to hear a pulsating sound. At this time, the pressure value indicated by the manometer is equivalent to the systolic pressure.

5) Continue to deflate slowly.

6) When the stethoscope hears the sound accompanying the heartbeat, it suddenly weakens or disappears. At this time, the pressure value indicated by the manometer is equivalent to the diastolic pressure.

7) After using, deflate the gas, tilt the sphygmomanometer to the right by 45 °, and turn the mercury switch into the mercury pot, then turn off the mercury switch ^[1] .

Sphygmomanometer precautions

Because of the direction of blood flow, the blood pressure measured by the left hand and the right hand will usually be slightly different; usually the blood pressure value of the left hand will be slightly higher than the right hand, but the difference is normal between 10 ~ 20mmHg, however, high measurement data should be used when recording Prevail. If the difference between the two hands is more than 40-50mmHg, the blood vessel may be blocked. It is best to ask the doctor to find out the cause.
It is not advisable to measure blood pressure only once. You should measure blood pressure several times during the day and record it in order to understand the change of your blood pressure during the day.
Most commercially available sphygmomanometers are mainly electronic, and their measurement results are usually slightly higher than traditional mercury sphygmomanometers. Electronic sphygmomanometers are divided into wrist and arm types. Although the wrist type is more convenient to use, it is usually far away from the heart and the greater the difference in measurement results; it is recommended to test it on the spot when purchasing. There is not much difference in the measured results, both can be used; if the difference is large, it is better to choose the arm type.
Before and after the mercury sphygmomanometer is used, medical staff should always pay attention to check the blood pressure and keep the scale clear. The column should be cleaned regularly with a strip. There should be no air bubbles when the pressure is about 200 mmgH. Carry out inspection and maintenance ^[4] .
It is best to measure blood pressure in a relaxed mood in your own home. When some people take blood pressure in a medical hospital, they will be nervous because they face the medical staff wearing white clothes, which will increase blood pressure. This can be overcome by measuring blood pressure at home.
Traditional mercury sphygmomanometers are affected by thermal expansion and contraction, and should be adjusted to zero every six months on average.
Electronic sphygmomanometers are affected by the aging of components, etc., and need to be calibrated once every year on average.

Sphygmomanometer Extended Reading

[1] Liang Ai. How to choose and use a home sphygmomanometer [J]. Cardiovascular Disease Prevention and Treatment Knowledge (Science and Technology Edition), 2018 (03): 25-26.

[2] Liu Jinlai. Learn to measure blood pressure with electronic sphygmomanometer [J]. Yi Shou Bao Dian, 2017 (21): 14-15.