What Are the Different Types of Blood Pressure Equipment?

Blood pressure meter, an instrument that measures blood pressure is called a blood pressure meter. The blood pressure of the wrist band is used to force the measurement site to block the blood flow, and then the blood is allowed to flow again by discharging the gas in the wrist band. Blood pressure measurement is based on changes in blood flow sounds and vibrations that occur when blood is flowing again.

Blood pressure meter

Blood pressure meter, an instrument that measures blood pressure is called a blood pressure meter. Impulse pressure is blocked by the wrist arm band

There are two measurement methods:

Use a microphone to remove the sound during blood circulation (this sound is called Korotkoff sound). With hospital measurements (

Clinical significance of accurate blood pressure measurement: Generally speaking, abnormal blood pressure means the presence of cardiovascular and cerebrovascular disease. In clinical medicine, blood pressure value is an important human health parameter to provide a basis for the treatment of cardiovascular and cerebrovascular diseases. However, if the blood pressure measurement error is large, or even the wrong measurement result, it will inevitably lead to a diagnosis error and a treatment method. And taking medication errors.

Accurate measurement of blood pressure is the premise of quantitative analysis of the cause of abnormal blood pressure. There are many factors that affect human blood pressure, such as blood volume, degree of atherosclerosis, heart function, endocrine, exercise, mood, etc., but what factors and how much influence must be determined by accurate blood pressure measurement. If the error in blood pressure measurement is large enough to cover up these influencing factors, the premise of quantitative analysis of the cause of abnormal blood pressure will no longer exist.

Therefore, the accurate measurement of blood pressure will provide an important basis for the treatment of cardiovascular and cerebrovascular diseases, and provide an accurate reference for further research on hypertension theory.

All blood pressure abnormalities must have their causes, and as long as the causes are resolved, the blood pressure abnormalities are not incurable. The treatment of abnormal blood pressure depends more on the further development of hypertension theory. On the road of accurate blood pressure measurement, among countless people's exploration practice, from invasive to noninvasive, from complex to simple, from rough to accurate, four major changes in blood pressure measurement methods (methods), each time for the medical community Development has had a profound impact.

Invasive intubation blood pressure measurement

Invasive intubation blood pressure measurement was Marey's earliest discovery of the pressure fluctuations during the pressure of the fluid bag in 1876, and found that the amplitude of the pressure fluctuations changed slightly from the pressure of the fluid bag from diastolic pressure to systolic pressure After reaching the maximum value, it starts to decline again. Many researchers then established physical models, mathematical models, and animal and human experiments to analyze the meaning of the maximum amplitude of pressure waves and confirmed that there is a good correspondence between the maximum amplitude and the average pressure. At present, the maximum pressure method is usually used to judge the average pressure.

Advantages of invasive intubation blood pressure measurement: It is the most ideal standard for high accuracy of blood pressure measurement. Because invasive cannula measurement is to insert a cannula into a blood vessel, it is like a direct investigation of the nature of things, rather than hearsay.

Disadvantages of invasive intubation blood pressure measurement: the catheter must be inserted into the blood vessel by surgery, so certain equipment and specialized medical staff are needed, and the patient suffers a lot of pain during the measurement, and is generally only used during surgery , Used in cardiac surgery to prevent other methods from measuring the impact caused by untimely or inaccurate.

Coriolis

Coriolis measurement is also called mercury mercury measurement, which belongs to non-invasive blood pressure measurement method. In 1905, Russian scholar Kolotkov discovered that the upper arm was strapped and pressurized with an armband to compress the brachial artery blood vessels, and then decompressed. As the external pressure decreases, it can be heard from the stethoscope inside the armband. After the blood flow reopens the blood vessel, the friction and impact sounds synchronized with the pulse are emitted. Because of the importance of this discovery, this friction and impact sound was named Coriolis.

Koch's measurement of blood pressure by cuff pressure and listening to pulse sounds has solved the non-invasive method of manometry, which has made great contributions to human medicine. Until now, many doctors still use this method to measure blood pressure. This method is the Coriolis method. Today, it has been more than a hundred years since the Coriolis blood pressure measurement method was invented. Due to the limitation of technology, there is no accurate performance of any blood pressure measurement method in this century. The international standard for blood pressure measurement. But this does not mean that the accuracy of the Kelvin method is completely trustworthy. It has more errors and other uncertainties than other blood pressure measurement methods:

A. The doctor must constantly observe the changes in the mercury manometer when listening to the sound. Because people's reactions are different, there is a certain gap in reading the blood pressure value: the little nurse and the old professor measure blood pressure differently. The child can see the reading on the blood pressure meter, and the old professor may have a lower reading because of the slow response.

B. Different people's hearing and resolution are different, and there are differences in the distinguishing of characteristic sounds (that is, in time). Due to the different Coriolis sounds produced by different people, the sounds can vary greatly. If the generated sound is small, it may not be heard in time. When heard, it is already the Coriolis sound after the blood has flowed through the blood vessel for a while.

C. The speed of deflation has a direct impact on the reading. The international standard deflation speed is 3 ~ 5mmHg per second, but some doctors often deflate quickly, affecting the accuracy of the measurement. The pulse wave sphygmomanometer deflation speed is 3 ~ 5mmHg / pulse beat, control is accurate.

D. Since there is no intuitive comparison method for listening to Coriolis, many aspects are related to subjective factors, doctors' proficiency, and technology.

E. Due to the discontinuity of the heart beat, the time difference between two adjacent beats multiplied by the falling speed of the mercury column is an inevitable error of the Coriolis auscultation method. All things have an internal connection. When measuring blood pressure, there are several premises. The person being measured is unchanged. The character is immobile during the measurement. The character is in a stable state during the measurement. The working state of the heart is stable. The smooth operation of the heart makes the blood flow in the blood vessels within a standard time constant. The only change is the pressure of the balloon, which is related to blood flow. The pulse wave sphygmomanometer uses the internal relationship between pulse wave and blood pressure to measure. It can continuously measure the change between blood pressure and pulse wave, even if the blood pressure value is between the two beats of the heart.

F. The sound and blood flow are not synchronized. When a Coriolis sound is generated, there is not necessarily blood flow; when a blood flow is generated, there is not necessarily a Coriolis sound.

G. Generally speaking, when the blood pressure is measured manually, different doctors have different measurement results on the same person at different times. Normally within 5 to 15 mmHg is considered a normal difference.

In the process of measuring blood pressure using the Kelvin method, many errors will not be ignored. What's more, the assumption that the König sound accurately measures blood pressure is not possible:

Hypothesis 1: When the cuff is pressurized, the external balloon pressure is the same as the blood pressure inside the brachial artery. However, if the subject's body is too obese and the flesh is thick, the pressure of the balloon will be greater than the blood pressure in the blood vessel to measure the blood pressure. If a person's blood vessels age, it will be difficult to block them from outside pressure, just like rubber pipes and steel pipes. The same force can flatten rubber pipes, but not flatten them. Because the pressure of the external balloon is greater than the blood pressure in the blood vessel, the measured blood pressure value will be higher than the actual blood pressure value, which is pseudohypertension.

Hypothesis 2: The hypothesis that there must be sound when there is blood flow in the arteries is also not true. It's like blowing a whistle, someone who knows can blow a little bit of air, and can't blow without exhausting their energy. The sound of blood flowing into the static blood vessels is also similar. It varies from person to person, there is great uncertainty, and pseudohypotension will also occur.

Further reading:

Pseudo-hypotension is the measurement of blood pressure by the Coriolis method, due to the unsynchronization of sound and blood flow (that is, there is not necessarily a Coriolis sound when blood is flowing), until the cuff balloon pressure decreases to a certain value, After the blood flow increases, the first Coriolis sound is emitted, which causes the blood pressure value measured by the Coriolis method to be smaller than the true blood pressure value.

According to statistics, in today's highly developed medicine, the main cause of cerebrovascular accidents is pseudohypotension. The wrong blood pressure measurement results in the wrong medication or wrong treatment, and the wrong medication use or treatment method directly leads to the worsening of the patient's condition and even death!

How to determine false hypotension

1. When measuring the blood pressure by using the Coriolis method, in addition to listening to the Coriolis with a stethoscope, you can touch the radial artery of the test subject with your fingers. When the airbag pressure gradually decreases, the fingers feel that the radial artery begins to beat gradually from small to large. When the stethoscope heard the first Coriolis sound simultaneously. If it is synchronized, there is no false low pressure, and the Coriolis method will give a correct blood pressure measurement. If it is not synchronized, it will be a false low pressure, and the Coriolis method will give an incorrect blood pressure measurement. This measurement error can sometimes reach tens of mmHg. (Because the sensitivity of pulse pulsation is too low, it is easy to cause new errors. It is recommended that this method is generally not used.)

2. When using the Coriolis method to measure blood pressure, use a pulse wave sphygmomanometer to measure simultaneously. If the readings are the same, there is no false low pressure. The Coriolis method gives the correct blood pressure measurement. If they are not the same, then It is a false hypotension, and the Coriolis method gives an incorrect blood pressure measurement.

Oscillometric method

The oscillometric method, also called the oscillation method, is a relatively advanced electronic measurement method developed in the 1990s. The principle is briefly described as follows: First, the cuff is strapped to the arm, and the cuff is automatically inflated. After a certain pressure (generally 30 to 50 mmHg higher than the systolic pressure), the pressure is stopped and the air is released. When the air pressure reaches a certain level, The blood flow can pass through the blood vessels, and there is a certain oscillating wave. The oscillating wave is transmitted to the pressure sensor through the trachea. The pressure sensor can detect the pressure and fluctuation in the cuff in real time. As the air is gradually deflated, the oscillating wave becomes larger and larger. Re-deflate As the contact between the cuff and the arm becomes looser, the pressure and fluctuation detected by the pressure sensor become smaller and smaller.

Select the moment with the most fluctuation as the reference point. Based on this point, look forward to the fluctuation point with a peak value of 0.45, which is systolic pressure, and backward look for the fluctuation point with a peak value of 0.75. The pressure corresponding to this point is diastolic pressure. The pressure corresponding to the point with the highest fluctuation is defined as the average pressure. It is worth mentioning that the two constants of 0.45 and 0.75 are not the same for each manufacturer, and are determined based on the statistical results of clinical tests.

Oscillometric sphygmomanometer is a very popular sphygmomanometer. 80% of the sphygmomanometers owned by families are oscillometric sphygmomanometers. To say that it is advanced is only technically advanced in the electronic instrument for measuring blood pressure, but the core measurement technology (ie, the oscillometric method) has some defects.

Since the value measured by the oscillometric method is fluctuating, there is no regularity, and there may be several maximum values. According to the calculated data, the value of blood pressure cannot truly reflect the value of blood pressure. So oscillometric measurement of blood pressure is also based on the assumption:

First, the subject's waveform is standardized. But standardized waveforms are built on mathematical models. In real life, everyone's waveforms are different. There are few similar to standardized waveforms, which can be ignored.

Secondly, the formulas and coefficients used to calculate blood pressure (0.45 and 0.75) are the same as those of the test subjects. Generally speaking, healthy people can roughly meet the coefficients, and unhealthy people often do not. But only those with poor health need a blood pressure monitor for blood pressure measurement.

The oscillometric method is based on a large number of crowd experiments and is given by statistical methods. Therefore, this measurement method will inevitably cause measurement errors in some people, sometimes the errors can reach tens of millimeters of mercury. The measurement error of the oscillometric method is larger than that of the Coriolis method. Although there are some measurement errors of the Coriolis method, in the international standard, the Coriolis method is used instead of the oscillometric method as a control instrument for detecting measurement errors of blood pressure monitors. .

According to scientific statistics, the oscillometric method is only applicable to 70% of the population, and the remaining 30% is not applicable. For the same person, since the blood waveform of a person changes, the sphygmomanometers measured at different times may be different.

In order to verify the technical deficiency of the oscillometric sphygmomanometer, we can do the following two simple experiments to prove it:

Experiment 1: Replace the arm with a shaking water bottle and observe the reading of the oscillometric sphygmomanometer

A mineral water bottle is used to hold 3/4 water. The sphygmomanometer cuff balloon is fixed outside the mineral water bottle, and the mineral water bottle is rhythmically shaken. Even if there is no real blood flow, the oscillometric sphygmomanometer will still give The reading proves that the reading of the oscillometric sphygmomanometer is unreliable under certain conditions.

Experiment 2: Measurement of blood pressure after exercise

The oscillometric sphygmomanometer uses empirical data to determine blood pressure readings, but it is only suitable for blood pressure measurement in a calm state, and cannot be used to measure blood pressure after exercise. During exercise blood pressure measurement, the pulse wave sphygmomanometer and oscillometric sphygmomanometer are used to measure the blood pressure of both arms at the same time, and the blood pressure value is recorded. It can be found that the oscillometric sphygmomanometer cannot measure blood pressure after exercise because of too large an error.

Pulse wave measurement

The pulse wave blood pressure measurement method was successfully developed in 2012, and has now obtained an invention patent issued by the China National Patent Office, and has applied for an international patent.

The pulse wave sphygmomanometer uses an upper arm cuff and a downstream pulse wave detection method to transform the discontinuous event of pulse beat into continuous measurement. On the one hand, based on the measurement of the amplitude of the pulse wave in the vicinity of the systolic blood pressure, it basically changes linearly, instead of judging the Coriolis sound from scratch, avoiding the inevitable possible errors caused by the discontinuity of the heart beat, and it can be accurately non-invasive Measure the systolic pressure in blood pressure; on the other hand, based on measuring the time characteristics of the delay time between the pulse wave and the corresponding barometric AC signal near the diastolic pressure, instead of judging the presence of the Coriolis sound, it also avoids the heart The inevitable possible errors caused by pulsatile discontinuities can accurately and non-invasively measure diastolic blood pressure in blood pressure.

Due to the inevitable error of the Coriolis sound, the pulse wave sphygmomanometer data will be higher than the data obtained by the Coriolis sound method when using the Coriolis sound measurement and pulse wave measurement at the same time, which can explain the pulse Sphygmomanometers can effectively avoid false hypotension. In the process of measuring blood pressure, when the first pulse wave appears, it means that the blood pressure is equal to the cuff pressure, and the blood flow can just break through the cuff pressure and recirculate. The pressure at this time is the human systolic pressure; when the cuff pressure is lower than the diastolic pressure The blood is not subject to external pressure and there is no delay time of the pulse wave. The pressure value measured at this time is the diastolic pressure of the human body.