The basic knowledge of the monitor 2

Blood pressure part

The production of blood pressure in human body

The body's blood vessels and heart form the body's blood circulation system, blood to circulate in the body, there must be pressure difference, there is a power device with differential pressure. This power device is the heart. The heart contracts the blood through the heart, passes through the artery to the whole body, and the blood passes through the vein to return the heart, while the heart relaxes. In this way, we have to work more and more. True blood pressure is a fluctuating process. Arterial pressure is high and fluctuating. Venous pressure is low and fluctuates little. The blood pressure we usually say refers to the pressure of the arteries.

Cokoli sound method

The first method used by Kirsch is to squeeze blood vessels through the cuff and air pressure, so that the blood flow is completely blocked by the stethoscope, and then the sound of the blood vessels is not heard, and then the pulse sound is slowly released to hear the pulse. At this time, it is believed to be the pressure of contraction. Continue to bleed through the stethoscope can hear strong and strong pulse, and gradually lighter, until it can hear a smooth and normal pulse. At that time, the blood vessels were completely uncompressed, that is, the low pressure, that is, diastolic blood pressure. The method of measuring blood pressure through cuff pressure and pulse sound to measure blood pressure is a great contribution to human medicine. Many doctors are still using this method to measure blood pressure.

Meilun The advantage of the Kolson sound method is that it is simple in measurement, but it also has the disadvantage that different people may detect different results and sometimes differ greatly. The main reasons are:

(1) when doctors listen to the sound, they should keep observing the mercury pressure gauge. Because of different reactions, there is a certain difference when reading the blood pressure.

(2) different people have different listening and discriminating abilities, and there are differences in the recognition of characteristic sounds (i.e. time).

(3) the speed of air bleed has a direct effect on readings, and the rate of international standard deflation is 3~5mmHg per second. However, some doctors tend to deflate faster and affect the accuracy of measurement.

(4) since there is no intuitive comparison method for hearing pulse sounds, there are many aspects and subjective factors. And it is related to the skill and skill of the doctor.

Generally speaking, when the blood pressure is measured manually, different doctors have different results for the same person at different times. Normal differences are usually considered within 5 to 15mmHg.

Vibration wave method

Vibration wave method is a relatively advanced method of electronic measurement developed in 90s. The principle is as follows: first, the cuff is tied to the arm and the cuff is inflated automatically to a certain pressure (usually 180~ 230 mmHg). When the pressure is to a certain extent, the blood flow can pass through the blood vessel, and there is a certain oscillation wave. The wave is transmitted to the pressure sensor in the machine through the trachea. The pressure sensor can detect the pressure and wave in the cuff in real time. Gradually deflation, the oscillating waves are getting bigger and bigger. Due to the loosening of the cuff and arms, the pressure and fluctuation of the pressure sensor are getting smaller and smaller. As shown in Figure 3a, 3b. We choose the maximum fluctuation time as the reference point, based on which we look forward to the peak 0.45 fluctuation point, which is high pressure (i.e., systolic pressure) and backward looking for peak 0.75 fluctuation point, which corresponds to the pressure of low pressure (diastolic pressure), and the stress at the highest fluctuation point is flat. Mean pressure. It is worth mentioning that 0.45 and 0.75 are the constant. For all manufacturers, they are not feeding, and must be based on clinical results. Once determined, they are constant. I will not discuss these feature points' recognition and algorithms anymore. The advantages and disadvantages of this measurement method are discussed below.

Its advantages are:

(1) compared with the kolkman sound method, a pulse sound part is omitted, and it is more economical.

(2) it is not easy to be affected by the pulse strength of the tested people, because the identification of its characteristic points is proportional to the maximum pulse wave.
(3) repeatability and good consistency.

(4) the accuracy is high. The setting of parameters is derived from clinical results and is more objective.
Its main shortcomings are:

(1) it is susceptible to external vibration, such as artificial vibration cuff, tracheal vibration, human body movement and so on.

(2) low pressure measurement is susceptible to the deflation rate and rigidity of the trachea.

Blood pressure measurement

(1) first of all, we need to make a clear point that human blood pressure is not a relative fixed value like weight or height, but is constantly changing. When people are excited, nervous and exercise, their blood pressure will increase, while their blood pressure should be lowered after drinking, taking a shower or smoking. The medical test proved that a normal person, the blood pressure in a day is fluctuating, the blood pressure is the lowest when people are sleeping, the blood pressure is the highest at 8 to 10 a.m., the amplitude of the normal person's systolic pressure (high pressure) in one day is between 20 and 40mmHg, and the diastolic pressure (low pressure) changes between 10 and 20mmHg, even between the normal people. At night, people also fluctuate 5 to 10mmHg during sleep. Some people say that the blood pressure measured by the doctor is 80 to 20mmHg. But at home, the numbers measured by electronic sphygmomanometer are always different. In fact, the value measured by electronic sphygmomanometer reflects the value of blood pressure at the time of anthropometry. As you can see from the chart, the blood pressure of the human body is constantly changing, and the same blood pressure value is very rare when measured two times. Therefore, only by measuring blood pressure at the same time and at the same time every day can we get comparable blood pressure.

(2) postures in measurement also affect the measurement results. Research knot