blood pressure measurement

British physiologist S. hales was the first to measure arterial blood pressure of living animals by acute experiment. 1733, he connected a copper cannula to the femoral artery of the horse and then connected it with a long glass. When the femoral artery is opened and ligated, the horse's arterial blood column rushes into a glass tube as high as 2.5 meters, and rises and falls with the beating of the horse's heart. This method of measuring blood pressure is called direct measurement.

Due to the inconvenience in operation, J.-L.-M. Marie Poi, a French physiologist and physicist, switched to mercury manometer in 1823, and connected the arterial cannula filled with anticoagulant to the arteries of experimental animals to measure arterial blood vessels. 1847, German physiologist C.F.W Ludwig further used a U-tube mercury manometer, one end of which was connected with the artery of experimental animals, and the other end was connected with a mercury column with a buoy. The pen tip was uploaded and the fluctuation of arterial pressure was continuously recorded on a rotating marking drum, which was a great progress in the methodology of experimental physiology. This method is still widely used in general acute animal experiments, but it can not be used in human body because of its serious harm to the body.

Indirect method is usually used to measure arterial blood pressure of human body, which was invented by Russian doctor N. Korotkov. The device includes an inflatable cuff and a pressure gauge connected to it. Tie the cuff to the upper arm of the subject, and then inflate it until the blood flow of the brachial artery is blocked and the air in the cuff is slowly released. The stethoscope placed on the brachial artery can hear the vibration sound caused by turbulence when the blood flow in the cuff is just lower than the blood pressure of the brachial artery (Korotkov's). Continue to deflate, and the Coriolis sound will increase. When the sound becomes deeper and longer, the measured blood pressure reading is equivalent to the lowest blood pressure in diastolic period, which is called diastolic pressure; When the internal pressure in the cuff is lower than the diastolic pressure, the blood smoothly passes through the unobstructed blood vessels, and the Coriolis sound disappears.

Because the specific gravity of mercury is too large, it is difficult for mercury manometer to accurately and quickly reflect the instantaneous changes of blood pressure at various stages of heartbeat, so various sensitive membrane manometers can be used to measure systolic and diastolic blood pressure more accurately later. In recent years, the combination of various sensors and oscilloscopes can be used to measure and record blood pressure more sensitively. National authorities released normal blood pressure:

Systolic blood pressure < 130mmHg, diastolic blood pressure

Ideal blood pressure: systolic blood pressure

Mean normal blood pressure reference value (mmHg) of China people age systolic blood pressure (male) diastolic blood pressure (male) systolic blood pressure (female) diastolic blood pressure (female)16-201573107021-25. 438+0 10 7 1 26—30 15 75 16 5438+02 73 3 1—35 16 5438+07 76 14 74 36—40 1 20 80 65438 6 ~ 65438+February 90 ~105 (12 ~ 65438) 438+04.0) 40 ~ 50 (5.0 ~ 6.7) 2 ~ 7 years old 85 ~105.

Because of the obvious fluctuation of blood pressure, it is necessary to measure it repeatedly on different days to judge whether the increase of blood pressure is persistent. At present, the following three methods are used to evaluate blood pressure level.

1, self-test blood pressure

Self-measured blood pressure refers to the blood pressure measured by subjects at home or in other environments, which is referred to as self-measured blood pressure for short. Self-measured blood pressure has the following six meanings:

1. Distinguish between persistent hypertension and "white coat" hypertension. Blood pressure measured at home should not exceed 135/85 mm Hg.

2. Evaluate the efficacy of antihypertensive drugs.

3. Improve patients' compliance with treatment.

4. It may reduce the cost of treatment.

5. Self-test blood pressure has time flexibility. For example, some hypertensive patients' blood pressure rises at 5 ~ 6 o'clock or 19 ~ 20 o'clock, so it is easy to miss the diagnosis by occasional clinical blood pressure measurement, and these patients can be easily found by self-testing blood pressure.

6. Observe regularly. To know the changes of blood pressure during treatment in time and provide more perfect data for diagnosis and treatment.

The specific method of self-measuring blood pressure is basically the same as that of occasional blood pressure measurement in clinic. Mercury sphygmomanometer can be used, but Coriolis auscultation must be trained. Generally speaking, it is recommended to use an upper arm automatic electronic sphygmomanometer that meets international standards (ESH and AAMI). Semi-automatic electronic sphygmomanometer, wrist electronic sphygmomanometer and finger cuff electronic sphygmomanometer are not recommended. When self-testing blood pressure, the average of three readings is also recorded, and the date, time, place and activity of measurement are also recorded. Generally speaking, the self-rated blood pressure value is lower than the clinical blood pressure value. At present, there is no unified normal value of self-measured blood pressure, and 135/85mmHg is recommended as the upper limit reference value of normal.

2. occasionally measure blood pressure in the clinic

At present, occasional blood pressure measurement is a standard method for clinical diagnosis and grading of hypertension, which is measured by medical staff under standard conditions according to unified norms. The specific requirements are as follows:

1. The environment for measuring blood pressure should be quiet and the temperature should be appropriate. Rest for at least 5 minutes before measurement. Smoking, drinking strong tea or coffee and urinating are prohibited half an hour before the exam. Avoid nervousness, anxiety, emotional excitement or pain.

2. Subjects generally take a sitting position, measure the right upper arm and relax the muscles of the whole body; Don't roll up the sleeves too much or too thick and squeeze them on the cuffs. The elbow should be at the same level as the heart.

3. The airbag of the cuff should surround 80% of the upper arm, and the lower edge of the cuff should be 2.5cm above the elbow. Put the chest radiograph of the stethoscope on the brachial artery at the elbow fossa below the cuff (do not put the chest radiograph of the stethoscope into the cuff), and gently press it to make the stethoscope fully contact with the skin, and do not use too much force.

4. When measuring, inflate quickly, and the pressure in the airbag should reach the point where the wrist radial artery pulsation disappears, then increase the mercury column by 30mm (mmHg) and then deflate it slowly, so that the mercury column will drop at a uniform speed (2-5 mmHg/s). The systolic blood pressure is the scale value of the protruding height of the mercury column when the sound of 1 is heard; Diastolic pressure is the reading when the sound disappears. In the case of children, pregnancy, severe anemia or aortic valve insufficiency, the auscultation sound does not disappear, and it is changed to diastolic pressure at this time. After obtaining the diastolic blood pressure reading, quickly deflate to zero (0) level.

5. The measurement should be repeated twice with an interval of 2 minutes each time. Take the average of the two readings and record. If the difference between the two readings of systolic or diastolic blood pressure is greater than 5mmHg, the third measurement should be made every 2 minutes, and then the average of the three readings should be taken.

3. Ambulatory blood pressure monitoring

Ambulatory blood pressure monitoring should use monitors that meet international standards (ESH and AAMI). The subjects were in a state of daily life. The pressure measuring interval is 15 ~ 3 1 min, and the pressure measuring interval between day and night should be the same as much as possible. Generally, it is monitored 24 hours a day. If it is only for diagnostic evaluation, only daytime blood pressure can be monitored.

Ambulatory blood pressure monitoring provides the average and dispersion of 24-hour, day and night blood pressure, which can sensitively and objectively reflect the actual blood pressure level, blood pressure variability and blood pressure circadian rhythm, and is more closely related to target organ damage and prognosis than occasional blood pressure measurement in clinic. Matters needing attention when measuring blood pressure:

1. The sphygmomanometer should be checked regularly, kept accurate, placed stably, and not inverted or vibrated.

2. Don't inflate too high or too hard. After use, the air in the cuff is driven out and rolled up. Rubber balls must be placed in a fixed position in the box to prevent the glass from breaking. If there is a switch under the mercury column, turn off the switch after use. If bubbles appear in the mercury column, it should be adjusted or overhauled, and measurement with bubbles is not allowed.

3. If the sphygmomanometer is found to be inaudible or abnormal, it should be re-tested. Let the mercury drop to the "0" point and then measure it. If necessary, measure the upper arm for comparison.

4. People who need to closely observe blood pressure should try to set the sphygmomanometer in four settings: fixed, fixed and fixed.

5. Hemiplegic patients should be measured on the healthy arm.

6. Prevent the error caused by the sphygmomanometer itself: If the mercury column is insufficient, the measured blood pressure will be low. The vent hole at the upper end of the mercury column is blocked, making it difficult for air to enter and exit, which may cause the phenomenon of low contraction and high diastolic pressure.

7. In order to avoid the influence of blood flow, when measuring blood pressure, the "0" point of sphygmomanometer should be on the same level with brachial artery and heart. When sitting, the brachial artery is flat with the fourth costal cartilage; When lying flat, it is flat with the axillary midline. If the limb is too high, the measured blood pressure is often low and the position is too low, then the measured blood pressure is high. Blood pressure is measured in millimeters of mercury. According to WHO 1999 guidelines, the ideal systolic/diastolic blood pressure is below 120/80, normal blood pressure is below 139/89, and hypertension is above 140/90 to 160/95. Blood pressure allows blood to be transported to the whole body normally in arteries. If blood pressure is too low, blood can't be supplied to the whole body. On the contrary, if blood pressure is too high, it may damage blood vessels, which also reflects that there may be abnormalities in blood or heart. Blood pressure is affected by the following factors:

1. Height: The higher the body, the greater the pressure the heart needs to pump blood, so that blood can flow all over the body.

2. Age: The younger the age, the higher the metabolic rate, the greater the blood flow, and the more pressure the heart needs to pump blood. With the growth of age.

3. Blood viscosity (blood density): The thicker the blood, the greater the pressure the heart needs to pump it out.

4. posture: blood pressure is higher when standing than when sitting, and blood pressure is higher when sitting than when lying flat. Affected by the principle of gravity.

5. Vascular quality: If blood vessels become narrower, it is more difficult for blood to pass through, and the heart needs more pressure to pump out blood.

6. Others: mental state, life rhythm, personal differences, eating habits, drugs, heredity, weather changes, etc.

Unexpected blood pressure: the blood pressure measured by the subject without any reference.

Ambulatory blood pressure: Use an ambulatory blood pressure recorder to measure a person's blood pressure regularly within 24 hours day and night. Ambulatory blood pressure includes systolic blood pressure, diastolic blood pressure, mean arterial pressure, heart rate and their highest and lowest values. Any factor that can affect cardiac output and peripheral vascular resistance will affect arterial blood pressure.

Stroke output directly affects arterial blood pressure, with more cardiac output and higher blood pressure, less output and lower blood pressure. Output depends on stroke output and heart rate per minute. If the stroke output is constant and the heart rate increases, the arterial blood pressure will increase obviously, which generally has a great influence on diastolic blood pressure. The increase of cardiac output will shorten diastolic period, increase diastolic pressure and decrease pulse pressure. If the heart rate remains unchanged, only the stroke output increases, the systolic blood pressure increases obviously, and the diastolic blood pressure increases slightly, so the pulse pressure increases. Systolic blood pressure mainly reflects stroke output.

The change of vascular peripheral resistance has an effect on systolic blood pressure and diastolic blood pressure, but the effect on diastolic blood pressure is more obvious. The decrease of peripheral resistance reduces diastolic blood pressure and increases pulse pressure. Peripheral resistance increases, arterial blood pressure flow rate slows down, and arterial blood storage increases at the end of diastole, which increases diastolic pressure and decreases pulse pressure. It can be seen that diastolic pressure can reflect the magnitude of peripheral resistance. Hypertension patients will have increased peripheral vascular resistance due to arteriosclerosis, which will lead to a significant increase in arterial blood pressure, especially diastolic blood pressure.

The elasticity of arterial wall can buffer the increase of arterial blood pressure and reduce pulse pressure, which has a certain effect on maintaining normal arterial blood pressure in healthy adults. In the elderly, many vascular elastic fibers and smooth muscles are gradually replaced by collagen fibers, which greatly reduces the elasticity of vascular walls, weakens the role of buffering the increase of blood pressure, and leads to the increase of blood pressure.

Due to the influence of circulating blood volume, animals with normal closed circulation can basically adapt to the cardiovascular volume, make it full, and maintain an average circulating pressure of about 7 mm Hg. This value does not change much under normal physiological conditions, and is not an important factor for the significant rise and fall of arterial blood pressure. However, in severe blood loss, if the blood loss exceeds 30%, the circulating blood volume can not maintain the filling state of the cardiovascular system, and the average pressure of systemic circulation will drop to the point where it can not promote enough blood to return to the heart. Due to insufficient blood return, the cardiac output will be reduced, and in severe cases it can be reduced to zero mmHg. It can be seen that circulating blood volume is an important factor to determine arterial blood pressure.

The above factors affecting arterial blood pressure are the results of some analytical experiments. In the overall situation, there are often several factors that appear one after another and influence each other. For example, significant changes in heart rate will cause corresponding changes in cardiovascular system fullness and cardiac output. Changes in cardiac output can also cause changes in arterial blood flow velocity and peripheral vascular resistance. Under the regulation of neurohumors, all factors that can cause the change of cardiac output often cause the change of peripheral resistance of blood vessels, which is manifested by the corresponding rise and fall of blood pressure.