Is the electronic blood pressure monitor accurate?

This is the 4030th article of Da Yi Xiao Hu

As the public's health awareness increases, blood pressure monitors have become a must-have item for many families. However, the biggest concern people have when choosing a blood pressure monitor is whether the electronic blood pressure monitor is accurate. Before answering this question, let's review the development history of mercury blood pressure monitors and electronic blood pressure monitors. "Learning from history" can make us more rational when making choices.

In the early 18th century, a British priest connected a 9-foot-long glass tube to a copper tube and inserted it into a horse's leg artery. He measured the horse's blood pressure and made the water column in the vertical glass tube rise to a height of 8.3 feet, which pioneered blood pressure measurement. In 1819, a French doctor and physicist invented a method of measuring blood pressure using a mercury pressure gauge. Since then, various sphygmomanometers have been invented one after another. However, these methods not only damage blood vessels, but are also inconvenient and difficult to apply to the human body.

After 80 years of development, the real mercury sphygmomanometer was born in 1896. An Italian invented the world's first blood pressure meter that does not damage blood vessels. This sphygmomanometer consists of three parts: a rubber ball, a rubber cuff, and a glass tube filled with mercury. When measuring blood pressure, you only need to wrap the rubber cuff around your upper arm, squeeze the rubber ball, and observe the height of mercury in the glass tube to measure the blood pressure value. Compared with today's sphygmomanometers, it only lacks a stethoscope. In 1905, Russian Nikolai Korotkov used a stethoscope to listen to Korotkoff sounds to determine systolic and diastolic blood pressure. So far, the most classic modern method of measuring blood pressure with mercury sphygmomanometers, known as the "gold standard", was born. It took more than a hundred years for the mercury sphygmomanometer to be perfected from the theoretical foundation.

The development of electronic sphygmomanometers did not start with animal experiments, unlike mercury sphygmomanometers. The development of evidence-based medicine has accumulated a large amount of clinical theories for the development of electronic sphygmomanometers, the development of engineering mathematics has provided an algorithmic basis for it, and the manufacturing basis of integrated circuits has made it possible to create lighter and more accurate sphygmomanometers. With such a strong foundation, it is not difficult to create an electronic sphygmomanometer that can perform accurate measurements.

The current understanding of blood pressure is very different from the past. In the past, people paid more attention to the results of one or several blood pressure measurements, but now they pay more attention to the changing trend of blood pressure. Here we introduce the views of AHA (American Heart Association) on blood pressure measurement.

(I) In all of clinical medicine, blood pressure measurement is one of the most important measurements; unfortunately, its value is also one of the least accurate results.

(II) The current "gold standard" for checking blood pressure is to be measured by trained medical staff using a mercury sphygmomanometer and Korotkoff sound technology. However, there is increasing evidence that this method may lead to a large number of hypertensive patients being misclassified and that patients whose blood pressure is normal in the clinic but elevated in other environments may be missed for diagnosis. There are three reasons for this result:

1. Improper or wrong measurement method. This error can be avoided.

2. Blood pressure fluctuations are an inherent property of blood pressure and cannot be avoided. The only way to reduce the impact of blood pressure fluctuations on measurement results is to increase the number of measurements. One or two measurements in the clinic can only roughly estimate the average blood pressure level.

3. When a doctor is present, the blood pressure of the person being measured tends to rise (i.e., the white coat effect). To avoid this factor, the only way to avoid this is to measure blood pressure outside the clinic.

In addition to the three reasons for inaccurate measurement by mercury sphygmomanometers proposed by AHA above, there are inevitable error factors in the measurement method (Korotkoff sound technique) itself, which requires the operator to coordinate his hands, eyes, and ears to accurately measure blood pressure.

(III) There are three ways to measure blood pressure that can be used to predict the adverse effects that high blood pressure may have on the human body: first, the average blood pressure level; second, the diurnal variation of blood pressure; and third, the short-term variability of blood pressure. All three types of measurement data require multiple measurements at different times to obtain, especially 24-hour continuous monitoring. Mercury sphygmomanometers are not suitable for long-term continuous monitoring.

From the above three viewpoints, we can draw two conclusions:

Conclusion 1

The mercury sphygmomanometer, which serves as the "gold standard", is not as accurate as everyone imagines, so there is no need for supporters of the mercury sphygmomanometer to sneer at the electronic sphygmomanometer.

Conclusion 2

Blood pressure measurements that have clinical predictive value must be measured multiple times, but electronic sphygmomanometers that are easy to control with automatic programs can easily do this and can automatically draw a blood pressure curve.

With the development of the times, the disadvantages of mercury-containing sphygmomanometers, especially their environmental and health risks, have gradually become apparent, and it has become necessary for humans to seek mercury-free sphygmomanometers. In addition, in the digital age, all walks of life are undergoing a digital revolution, and data that are easy to transmit and share on the Internet will be used more effectively, and the data generated by electronic sphygmomanometers are easy to transmit and share on the Internet.

Author: Wang Hailong, attending physician, Hematology Hospital, Chinese Academy of Medical Sciences