Frequently Asked Questions about Blood Pressure Measurement

Blood pressure, an indicator that everyone is very concerned about, is also one of the four vital signs of our human body (blood pressure, body temperature, heart rhythm, respiration). Blood pressure measurement is a necessary examination item.

For patients with hypertension, measuring blood pressure is more important, including many people have electronic sphygmomanometers in their homes. Dr. Clove also talked about the posture of measuring blood pressure. Apart from the posture, there are many details that are also of concern to everyone. Let’s answer a few questions that everyone has asked more.

Sit and measure? Lie down and measure?

Generally speaking, there is a certain difference between the supine position blood pressure and the sitting position in theory, mainly for domestic blood pressure measurement, which requires [3.1 line], i.e. The heart, brachial artery and sphygmomanometer 0 points are at the same level. However, in the supine position, the sphygmomanometer will bend sideways to ensure [3.1 line] and cause reading error.

It has been reported that the diastolic blood pressure measured in sitting position is 5 mmHg higher than that in supine position, and the systolic blood pressure measured in lying position is 8 mmHg higher than that in upright position. Moreover, various reports vary, and no clear and meaningful difference has been found at present.

Therefore, there is no clear stipulation on the body position for blood pressure measurement in the current guidelines. It is generally believed that when blood pressure is measured, as long as the upper arm measured by the patient is placed at the heart level, the sitting position, lying position and even standing position can be taken as required.

For convenience, most patients adopt sitting position clinically. It is suggested that patients should also try to take the blood pressure of sitting position as the standard when monitoring.

Left hand? Right hand?

When the left and right brachial arteries measure blood pressure, because the right brachial artery is the first branch of the aorta and the left brachial artery is the third branch, it consumes more energy than the right hand, so the blood pressure is low, and the right hand can approach the pressure on the unit area of the aortic sidewall more closely. At present, the right hand blood pressure is the main one in clinical practice.

The blood pressure of the two upper limbs of healthy people can vary from 5 to 10 mmHg. At the same time, about 20% of normal people have the blood pressure difference between the left and right upper arms > 10 mmHg (called the blood pressure difference between arms). Therefore, it is recommended that the blood pressure of the left and right upper arms should be measured during the first examination. When the blood pressure of the left and right upper arms is inconsistent, the blood pressure measured by the arm with the higher value shall prevail.

However, if the difference in blood pressure between arms lasts more than 20 mmHg, it is highly indicative of vascular diseases, such as aortic arch constriction and upper limb artery occlusion, Takayasu arteritis, arterial malformation, severe atherosclerosis, aortic dissection involving subclavian artery, etc. At this time, a doctor should be consulted in time for further examination to clarify the reason.

Before taking medicine? After taking the medicine?

Taking antihypertensive drugs will definitely affect the blood pressure level of patients. The current views on how to arrange the time for taking drugs and measuring blood pressure are as follows:

  • Before diagnosis of hypertension, blood pressure should be measured in order to make reliable evaluation of blood pressure and provide guidance for follow-up treatment. If the patient has already taken the drug by himself, blood pressure should be measured after stopping the drug for a period of time under the condition of ensuring safety.

For example, hydrochlorothiazide has a half-life of 15 hours. If you want to completely eliminate its influence on the human body, you should stop using the drug for at least 75 hours and about 3 days. Therefore, when you find that your blood pressure rises, you should go to see a doctor first and do not take the medicine yourself, so as not to interfere with subsequent treatment.

  • For those who have been diagnosed with hypertension and have taken drugs for a long time, the blood pressure measurement at this time is mainly to evaluate the blood pressure control situation after taking drugs so as to further adjust antihypertensive drugs. Therefore, the drugs should be taken at normal time at this time, and the blood pressure at different times of the day should be measured at the same time, such as early, middle and late, so as to fully understand the blood pressure control situation.

Some drugs are easy to cause postural hypotension, such as prazosin, dilating blood vessels, and sudden standing after taking drugs, which will lead to obvious reduction of blood returning to the heart and hypotension symptoms, such as dizziness and unstable standing. At this time, the blood pressure level of standing position should be measured additionally, and ambulatory blood pressure should be measured conditionally.

Manual test? Electronic measurement?

At present, there are mainly desktop mercury sphygmomanometers and medical automatic electronic sphygmomanometers. For patients to monitor blood pressure at home, electronic sphygmomanometers are now recommended.

The main reason is that mercury in desktop mercury sphygmomanometer is harmful to human body and environment, so special care should be taken about mercury leakage and cleaning and calibration should be carried out at least every six months.

The medical automatic electronic sphygmomanometer verified by international standards can automatically provide systolic blood pressure, diastolic blood pressure, mean arterial pressure, heart rate and measurement time, with simple operation and reduced measurement errors caused by human subjective factors.

Certification standards include: British Hypertension Association (BHS) and American Association for the Promotion of Medical Instruments (AAMI).

Another advantage of automatic electronic sphygmomanometer is that it can store data for later analysis.

As for the accuracy, the current research has not found that the accuracy of electronic sphygmomanometers is worse than that of desktop mercury sphygmomanometers. Therefore, it is recommended that hypertension patients use electronic sphygmomanometers when monitoring blood pressure at home.