How to measure your blood pressure correctly?

Author: Chen Zhou, Department of Nephrology, Shanghai Changhai Hospital

Reviewer: Mei Xiaobin, Chief Physician, Nephrology Department, Shanghai Changhai Hospital

Hello everyone! I am Dr. Chen Zhou from the Department of Nephrology. Today I want to share with you a very simple but very important topic: How to correctly measure your blood pressure?

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Friends who have read Dr. Chen's popular science should know that blood pressure is one of the important factors affecting our kidney function. If blood pressure is too high or too low, it will increase the burden on the kidneys and cause kidney damage. Moreover, blood pressure will also affect the health of other organs such as our heart, brain, and eyes. Therefore, we must measure our blood pressure regularly and keep records. In this way, we can timely detect and control abnormal blood pressure and prevent and treat related diseases.

So, how do we measure our blood pressure correctly? Let me introduce it to you from the following aspects:

Selection of blood pressure monitor

Sphygmomanometers are tools for measuring blood pressure, and there are many types and brands. However, not all sphygmomanometers are suitable for our own measurement. It is recommended that you choose an electronic sphygmomanometer (fully automatic upper arm type) as the first choice for home self-testing. This type of sphygmomanometer is simple, convenient, and relatively accurate. Just put the cuff on your upper arm, press the button, and you can start measuring. Moreover, this sphygmomanometer can also display information such as our heart rate and arrhythmia.

Of course, if you have the conditions, you can also choose a mercury sphygmomanometer as a backup. This type of sphygmomanometer has higher accuracy and stability, but it requires a stethoscope and is relatively troublesome to operate. It is mostly used in hospitals.

How a sphygmomanometer measures blood pressure

The electronic sphygmomanometer uses the oscillometric method to measure blood pressure. It requires a cuff airbag and an electronic display. The cuff airbag is put on the upper arm, automatically inflates to compress the artery, blocks blood flow, and then automatically deflates. A pressure sensor is used to detect the pressure and fluctuations in the cuff. When the airbag pressure is equal to the systolic pressure, the blood begins to flow, producing the largest fluctuation amplitude. When the airbag pressure is equal to the diastolic pressure, the blood flows completely, producing the smallest fluctuation amplitude. Based on the fluctuation amplitude and a certain coefficient and formula, the systolic and diastolic pressures are calculated and displayed on the electronic display.

The mercury sphygmomanometer uses the auscultation method to measure blood pressure. It requires a cuff balloon, a mercury column, and a stethoscope. The cuff balloon is placed on the upper arm and inflated to compress the artery and block the blood flow. Then the balloon is slowly deflated, and the stethoscope is used to listen to the arterial pulsation sound and observe the changes in the mercury column. When the balloon pressure equals the systolic pressure, the blood begins to flow and the first plop is heard. At this time, the height of the mercury column is the systolic pressure. When the balloon pressure equals the diastolic pressure, the blood flows completely and the last plop is heard or the sound disappears. At this time, the height of the mercury column is the diastolic pressure.

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Tips for measuring blood pressure correctly

The correct and scientific measurement method is the prerequisite for ensuring that blood pressure is accurate and objective. When measuring blood pressure, pay attention to the following points:

Quiet : Sit quietly for 5 to 10 minutes before measuring blood pressure. It is recommended to rest for 30 minutes after exercise before measuring. This is because exercise, mood, diet and other factors can affect our blood pressure level.

Sitting position : It is recommended to measure in a sitting position with your feet flat on the ground and try to breathe calmly. Do not talk, cough, yawn, etc. to interfere with the measurement results.

Cuff : The measuring cuff should be directly attached to the skin of the upper arm, preferably without clothes. The width of the cuff should account for 40% of the upper arm circumference, and the length should account for 80% of the upper arm circumference. The lower edge of the cuff should be 2 to 3 cm away from the elbow joint, and the air bag of the cuff should be aimed at the artery on the inner side of the upper arm.

Horizontal : The cuff is at the same level as the heart, the upper arm is straight and slightly abducted, and the palm is facing up. If the cuff is higher than the heart, it will cause low blood pressure; if the cuff is lower than the heart, it will cause high blood pressure.

Measurement : Some electronic blood pressure monitors only require you to press a button to start measuring. After the cuff is inflated, you will feel your arm being tightly gripped, and then the cuff will slowly loosen. This tightening and loosening will measure the upper pressure (systolic pressure) and lower pressure (diastolic pressure) of the blood pressure. If it is a mercury blood pressure monitor, you will need to use a stethoscope to listen to the arterial pulsation sound and observe the changes in the mercury column to determine the systolic and diastolic pressures.

Record : After measuring blood pressure, it is best to record it according to time, systolic pressure, and diastolic pressure. This will make it easier for us to observe the changing trends and patterns of blood pressure. If conditions permit, you can also use special software or APP to record and analyze our blood pressure data.

Special note : If it is the first time to measure your blood pressure, you need to measure both sides, and take the side with the higher value as the standard, because some people may have high or low blood pressure on one side. In the future, you can measure on the same side.

Attachment: Blood pressure self-test record form