In a cardiac cycle, arterial blood pressure changes periodically with the rhythmic contraction and relaxation of ventricles. Note that the highest value of arterial blood pressure rising during contraction is systolic blood pressure, and the lowest value of arterial blood pressure falling during ventricular relaxation is called diastolic systolic blood pressure and diastolic blood pressure. The average arterial blood pressure of normal adults is 70~ 105 mm Hg. The formula is as follows: average arterial pressure = (systolic pressure +2× diastolic pressure) /3. It can also be expressed as: average arterial pressure = diastolic pressure+1/3 pulse pressure difference.
Based on brachial artery blood pressure, the resting blood pressure of normal adults ranges from systolic blood pressure 90 ~139 mmhg (12.0 ~18.5 kpa) and diastolic blood pressure 60 ~ 89 mmhg (8.0 ~10/0.8). Blood pressure can be measured by mmH9 or kPa. The conversion relationship between mmHg and kPa is:1mmhg = 0.133 kpa1kpa = 7.5 mmhg.
physiological change
1. The blood pressure of age and sex gradually increases with age, especially the systolic blood pressure. Newborns have the lowest blood pressure, children are lower than adults, and women of the same age are lower than men. There is no significant difference after menopause.
2. With sleep, blood pressure fluctuates obviously day and night. Generally, the blood pressure is the lowest in the morning, and gradually rises after the morning exercise, and rises at night. When you are overworked or sleep badly, your blood pressure may be high.
3. Generally, the blood pressure of the right upper limb is about 10~20mmHg higher than that of the left upper limb, and the systolic blood pressure of the lower limb is 20~40mmHg higher than that of the upper limb.
4. Ambient temperature In a cold environment, blood pressure can be increased due to contraction of peripheral blood vessels, and slightly decreased due to expansion of skin blood vessels in a high temperature environment.
5. The blood pressure of standing position and figure is higher than that of sitting position, and the blood pressure of sitting position is higher than that of lying position, which is related to the compensation mechanism caused by gravity.
6. Other emotional excitement, strenuous exercise pain, smoking, etc. Can lead to an increase in systolic blood pressure, diastolic blood pressure is generally unchanged. In addition, excessive salt intake and drug use also have an impact on blood pressure.
Evaluation of abnormal blood pressure
1. Hypertension refers to adult systolic blood pressure ≥ 140mmHg or (and) diastolic blood pressure ≥90mmHg without antihypertensive drugs.
2. Adults with hypotension have a systolic blood pressure lower than 90 mm Hg and a diastolic blood pressure lower than 60 mm Hg, which is called hypotension and is common in patients with massive blood loss, shock and acute heart failure.
Pulse pressure change
(1) Increased pulse pressure: Malt exceeding 40 mm Hg is called increased pulse pressure, which is common in arteriosclerosis, aortic valve insufficiency and hyperthyroidism.
(2) Decreased pulse pressure: malt is less than 30 mm Hg, which is called malt decrease, and it is common in pericardial effusion, constrictive pericarditis, aortic stenosis, heart failure, etc.
Types and structure of sphygmomanometer
Structure: (1) Valve for conveying balloons and adjusting air pressure.
(2) cuff: the length and width of rectangular flat rubber cuff should meet the standard. The commonly used rubber cuff is 24cm long, 12cm wide, and the jacket is 48cm long. In summer, the woven cuff is about 135cm long, which is two centimeters wider than the upper limb cuff. Children's cuffs are required to be 5 ~ 10cm long and newborns' cuffs are required to be 2.5 cm wide. The baby is 12 ~ 13.5cm long and 6 ~ 8cm wide, and the child is 17 ~ 22.5cm long and 9 ~ 10cm wide. There are two rubber tubes on the rubber belt, one connected to the gas pipeline and the other connected to the pressure gauge.
sphygmomanometer
1) mercury sphygmomanometer: Also known as mercury sphygmomanometer, it consists of three parts: a double-scale glass tube with 0 ~ 300mm Hg (0 ~ 40kpa) is fixed on the inner wall of sphygmomanometer and calcium, and each cell is equivalent to 2mm Hg (0.5kPa). The advantage of mercury beads as sphygmomanometer is that the measured values are more accurate and reliable, but the weight is heavier and the glass tube is fragile.
2) Indicating sphygmomanometer: The four meters are disc-shaped, with scales on the front disc and a pointer in the center of the reading disc. B is just a blood pressure reading. Its advantage is that it is small and easy to carry, but it should be checked regularly with a mercury sphygmomanometer.
3) Electronic sphygmomanometer: There is a transducer in the cuff, which can automatically sample and control the microcomputer to automatically abandon the digital operation program, and the systolic and diastolic blood pressure pulse values can be obtained within a few seconds. Automatic digital sphygmomanometer can automatically complete everything by pressing one button. Its advantages are clear, intuitive and easy to use, and it can also eliminate the errors caused by the tester, insensitive hearing and noise interference, but it needs to be checked regularly.
Techniques for measuring blood pressure
Note: 1. Check the sphygmomanometer regularly. Before measurement, check that the sphygmomanometer and glass tube are not damaged, the scale is clear and there is no crack, the pressure balloon and rubber tube are not aging and leaking, the cuff bandwidth is narrow and appropriate, the mercury is sufficient and there is no fracture. Check the stethoscope: the rubber tube has no aging, tight connection and normal conduction.
2. For patients who need to observe blood pressure for a long time, setting four points, setting time, setting posture, setting posture and setting sphygmomanometer is helpful to the accuracy of measurement and comparability of control.
3. When measuring blood pressure for patients with hemiplegia, limb trauma or surgery, healthy limb measurement should be selected.
4. Before measuring blood pressure, if the patient is excited by exercise, smoking and eating, rest quietly. 15~30 minutes later.
5. Don't inflate too hard or too high to avoid mercury spillage.
6. When abnormal blood pressure is found, or you can't hear clearly, you should re-measure. When re-measuring, the air in the cuff should be driven away first, and the mercury column should be reduced to zero, and then the measurement should be made later. Generally, it is measured 2~3 times, and the average value is taken. It is feasible to measure the blood pressure of both limbs if necessary.
7. Exclude the factors that affect blood pressure. 1. The cuff is too wide to compress the great vessels, and the pulsation disappears before reaching the lower edge of the cuff, so the blood pressure on one side is low, the cuff is narrow, and the blood pressure on the other side is high. 2. Tightening the cuff makes the blood vessels compressed before inflation, and the measured blood pressure is low. The loose cuff makes the plastic bag spherical, which reduces the effective measurement area and leads to the increase of lateral blood pressure. 3. The brachial artery is higher than the heart level, and the measured blood pressure is low, while the brachial artery is lower than the heart level, and the measured blood pressure is high. 4. The line of sight is lower than mercury, which makes the blood pressure reading higher, and the line of sight is higher than mercury, which makes the blood pressure reading lower. 5. Slow deflation leads to venous congestion, which can make the measured diastolic pressure higher, and the deflation speed is too fast, which can lead to hearing blood pressure readings.