Understanding Blood Pressure Regulation Scientifically: Normal Range and Health Measurement Guidelines

Blood Pressure and its Regulation

1. What is Blood Pressure?

Through the previous introduction to the cardiovascular system, the concept of blood pressure is easy to understand. The human heart and blood vessels are interconnected, forming a essentially closed "pipeline system." A normal heart is a powerful muscular organ, like a pump, beating rhythmically day and night. The heart's contraction and expansion propels blood through the circulatory system. As blood flows through the blood vessels, both contraction and relaxation of the heart exert pressure on the vessel walls. When blood vessels dilate, blood pressure decreases; when blood vessels constrict, blood pressure increases. The pressure in the large arteries is highest when the heart contracts; this blood pressure is called systolic blood pressure (SBP), or "high pressure." The pressure in the large arteries is lowest when the left ventricle relaxes; this is called diastolic blood pressure (DBP), or "low pressure." The "blood pressure" we usually refer to is actually the blood pressure measurement in the brachial artery of the upper arm, an indirect reflection of the blood pressure in the large arteries. Blood pressure measurements on the right and left sides can often differ, with a difference as high as 10 mmHg and as low as less than 5 mmHg.

Normal blood pressure is a prerequisite for blood circulation. Blood pressure is maintained at a normal level under the regulation of various factors, thus providing sufficient blood to all tissues and organs to maintain normal metabolism. Both excessively low and high blood pressure (hypotension and hypertension) can have serious consequences; the disappearance of blood pressure is a precursor to death. This demonstrates the extremely important biological significance of blood pressure to the human body.

2. What is the unit of blood pressure?

kPa (kilopascal) or mmHg (millimeters of mercury). When measuring blood pressure with a mercury sphygmomanometer, the height of the mercury column, "millimeters of mercury," is used to express the level of blood pressure.

1 mmHg (millimeters of mercury) = 0.133 kPa (kilopascal)

7.5 mmHg (millimeters of mercury) = 1 kPa (kilopascal)

3. What should the normal blood pressure range be?

Normal blood pressure range: Systolic pressure between 90 mmHg and 140 mmHg, diastolic pressure between 60 mmHg and 90 mmHg.

4. How should blood pressure be measured?

Blood pressure monitoring is very important, especially for patients with unstable blood pressure or those already diagnosed with hypertension. It is essential to measure blood pressure regularly. Currently, the standard method for clinical diagnosis and classification of hypertension is measurement by medical staff in a medical institution under standardized conditions and according to uniform procedures. Specific requirements are as follows:

(1) The measurement environment should be quiet and at a suitable temperature. Rest for at least 5 minutes before measurement. Do not smoke, drink strong tea or coffee, and empty your bladder half an hour before measurement. Avoid tension, anxiety, emotional excitement, or pain.

(2) The subject should be seated. Measure the right upper arm, relax all muscles, and place the elbow at the same level as the heart.

(3) The cuff should wrap around 80% of the upper arm, and the lower edge of the cuff should be 2.5 cm above the elbow crease. Place the stethoscope chest piece under the cuff at the elbow crease on the brachial artery (do not place the stethoscope chest piece inside the cuff), and gently press to ensure full contact between the stethoscope and the skin; do not press too hard.

(4) Quickly inflate the cuff until the radial pulse disappears, then raise the pressure by 30 mmHg. Then slowly deflate the cuff, allowing the mercury column to drop at a constant rate (2–5 mmHg/second). The reading at the height of the convex side of the mercury column when the first sound is heard is taken as the systolic pressure; the reading when the sound disappears is taken as the diastolic pressure. After obtaining the diastolic pressure reading, quickly deflate the cuff to zero.

(5) Repeat the measurement twice, with a 2-minute interval between each measurement. Record the average of the two readings. If the difference between the two systolic or diastolic pressure readings is greater than 5 mmHg, wait another 2 minutes before taking a third measurement, and then record the average of the three readings.

In many cases, the subject needs to measure their own blood pressure at home or in other environments. Self-monitoring of blood pressure is economical, convenient, and flexible, and can be performed frequently to monitor blood pressure changes during treatment.

Methods for self-monitoring blood pressure: A mercury sphygmomanometer or an upper-arm fully automatic electronic blood pressure monitor conforming to international standards (ESH and AAMI) can be used. Semi-automatic, wrist, and finger cot electronic blood pressure monitors are not recommended. When self-monitoring blood pressure, record the average of 2-3 readings, along with the date, time, location, and activity. Self-monitored blood pressure values ​​are generally lower than those measured at a medical institution. Currently, there is no universally accepted normal value for self-monitored blood pressure; 135/85 mmHg is recommended as the upper limit of normal.