How to accurately measure blood pressure: Detailed explanation of blood pressure monitor selection and precautions.

What are the differences between measuring blood pressure at home and in a hospital?

Due to technological advancements, electronic blood pressure monitors are widely available, allowing many people to measure their blood pressure at home. One of the updates and emphasis in the "Guidelines for Primary Care Management of Hypertension in China (2014 Revised Edition)" is to encourage home blood pressure monitoring and steadily promote the use of internationally certified, qualified upper-arm automatic (electronic) blood pressure monitors, gradually replacing mercury sphygmomanometers. Home blood pressure monitoring, also known as home blood pressure monitoring, has obvious advantages: it allows for real-time monitoring of blood pressure, especially the effectiveness of medication. It is unaffected by the medical environment, thus avoiding the "white coat effect," and offers better repeatability.

Because home conditions are relatively relaxed, the standard readings are generally lower than those taken in a clinic. A home blood pressure reading of 135/85 mmHg is equivalent to a clinic blood pressure reading of 140/90 mmHg.

Note: Frequent home blood pressure monitoring is not recommended for patients with anxiety or depression, or those who have modified their treatment plans without authorization.

How to compare a standard mercury sphygmomanometer with an electronic blood pressure monitor?

When measuring blood pressure at home with an electronic blood pressure monitor, and there's a discrepancy between the self-measured blood pressure and the clinic blood pressure, we might question the monitor's accuracy. How can we compare an electronic blood pressure monitor with a standard mercury sphygmomanometer?

The usual method is to take two measurements, one with an electronic monitor and one with a mercury sphygmomanometer, and observe the difference. If the difference is small, we can assume the electronic blood pressure monitor is accurate; if the difference is large, we assume it's inaccurate. However, this method has some uncertainty.

First, even with a mercury sphygmomanometer, there will still be some difference between two measurements, especially for people who are not well-rested or whose blood pressure fluctuates easily. Second, if the clinic blood pressure was measured in the morning and the self-measured blood pressure was taken in the afternoon or evening, there will definitely be a difference, possibly exceeding 10 mmHg. Furthermore, an individual's blood pressure naturally varies between morning, afternoon, and evening; this difference is inherent to their own body. Even at similar times, blood pressure readings can differ between a clinic and home. This is because a person's level of relaxation differs depending on whether they are at home or in a clinic.

If the comparison is conducted under similar conditions, such as in a clinic or at home, the results seem more reliable.

So, is it possible to measure and compare blood pressure using two different monitors simultaneously?

Most electronic blood pressure monitors have detachable cuff tubing. Similarly, mercury sphygmomanometers also have detachable cuff tubing, and the two tubings are connected using a connector. Connect both the electronic and mercury sphygmomanometers simultaneously using the cuff on the electronic monitor and the T-connector on the stethoscope. The electronic monitor automatically inflates and deflates, displaying the measurement. For the mercury sphygmomanometer, the reading is read by listening to the sound changes on and off using the stethoscope. This allows for simultaneous comparison of the two readings. If the difference between the two readings does not exceed 10 mmHg, the electronic monitor can be considered accurate.

We should still be aware that blood pressure fluctuates and changes within a certain range. If you want to compare and monitor your own blood pressure, it's best to do so at relatively fixed times and under relatively fixed conditions. Don't compare wrist blood pressure monitors with mercury sphygmomanometers; they are not comparable.

What are the advantages of 24-hour ambulatory blood pressure monitoring?

Many medical institutions are now equipped with 24-hour ambulatory blood pressure monitoring systems. Its advantage is that it allows you to understand the changes in blood pressure throughout the day and night, enabling continuous monitoring. However, its standards differ significantly from clinic blood pressure.

Domestic reference standards recommend: 24-hour average <130/80 mmHg, daytime average <135/85 mmHg, nighttime average <120/70 mmHg. Under normal circumstances, the nighttime average blood pressure is 10%–15% lower than the daytime blood pressure. (Measurements should be taken using monitors that conform to international standards BHS and AAMI).

24-hour ambulatory blood pressure monitoring (ABPM) is primarily used to screen for borderline and mild hypertension, differentiate "white coat hypertension," identify non-dipper hypertension, assess morning peak blood pressure, and evaluate the effectiveness of medications. Its results cannot replace clinic blood pressure and are generally not used for the diagnosis of hypertension.

ABPM measurements are typically taken automatically every 20-30 minutes during the day and every 30 minutes or hour at night. Because measurements are taken during sleep, it can disrupt the patient's rest and is susceptible to interference. Therefore, the results must be screened and analyzed by a physician.