Blood Pressure Health Education: Hypertension Classification, Standards, and Key Points of Scientific Management

Hypertension (HT) is the most common cardiovascular disease. It is classified into primary and secondary hypertension. In reality, the cause of hypertension is unknown in the vast majority of patients; this is medically termed primary hypertension (PH or EH), also known as hypertension. Besides causing symptoms associated with hypertension itself, long-term hypertension can become a significant risk factor for various cardiovascular diseases and affect the function of vital organs such as the heart, brain, and kidneys, potentially leading to organ failure and even death.

The incidence of this disease varies depending on factors such as region, diet, environment, occupation, gender, and genetics. The World Health Organization (WHO) reports that large-scale population surveys conducted in countries such as Australia, Japan, New Zealand, and the United States have found a prevalence of 8%–10% of adults diagnosed with hypertension.

1. Blood Pressure Blood pressure refers to the lateral pressure exerted by blood on the walls of blood vessels per unit area, i.e., pressure intensity. Blood vessels are divided into arteries, veins, and capillaries, and blood pressure is correspondingly categorized as arterial blood pressure, venous blood pressure, and capillary blood pressure. The blood pressure we usually refer to is arterial blood pressure.

Arterial blood pressure is the pressure of blood flowing in arteries. The level of arterial blood pressure is related to blood volume, the force of heart contraction, blood output, and the resistance of small arteries throughout the body. Increased resistance in small arteries has a significant impact on the development of hypertension.

Smooth muscle fibers line the walls of small arteries. When these arteries contract, the lumen narrows, increasing resistance as blood flows through. To maintain normal blood flow, blood pressure rises. Conversely, when small arteries dilate, blood pressure drops. The contraction and relaxation of the smooth muscle fibers in the blood vessel walls are controlled by the autonomic nervous system, which is controlled by the brain and influenced by endocrine glands.

2. Systolic and Diastolic Blood Pressure
Blood pressure is the lateral pressure exerted by blood flowing through blood vessels on the vessel walls. It can be divided into arterial blood pressure and venous blood pressure. Normally, the blood pressure we refer to is the arterial blood pressure measured by a sphygmomanometer. When measuring blood pressure, it is compared to atmospheric pressure, and the higher the blood pressure, the higher the level of atmospheric pressure.

(1) Systolic blood pressure (SP): Also known as high blood pressure, it is the highest pressure exerted by blood against the arterial walls when the heart contracts. Its normal value is 90–140 mmHg.

(2) Diastolic blood pressure (DP): Also known as low blood pressure, it is the lowest pressure exerted by blood against the blood vessel walls when the heart relaxes. Its normal value is 60–90 mmHg.

3. Standards for Normal Blood Pressure
Blood pressure is generally measured in millimeters of mercury (mmHg) and kilopascals (kPa). These two units are convertible, with a ratio of approximately 7.5:1. For a rough conversion, multiply the mmHg value by 4 and divide by 30 to obtain the kPa value, and vice versa.

a. Normal blood pressure range: Systolic blood pressure is 90–140 mmHg (12.0–18.7 kPa), and diastolic blood pressure is 60–90 mmHg (8.0–12.0 kPa). Blood pressure above this range may indicate hypertension or borderline hypertension, while blood pressure below this range may indicate hypotension.

b. Recommended blood pressure range: Once hypertension is diagnosed, blood pressure should be controlled within the normal range as much as possible. For young patients with mild hypertension, blood pressure should be controlled below 135/85 mmHg. For older patients, blood pressure can be lowered to the normal range, i.e., below 140/90 mmHg. For those with isolated systolic hypertension, systolic blood pressure should also be controlled below 140 mmHg. If the disease has a long history or is complicated by coronary heart disease, diastolic blood pressure should not be lowered below 85 mmHg to avoid inducing acute myocardial infarction.

For hypertensive emergencies requiring immediate blood pressure reduction, treatment should be administered within a short period, but with certain limitations. Generally, the reduction should not exceed 25%–30% of the pre-treatment blood pressure, and should not be immediately lowered to normal.

Numerous studies both domestically and internationally have shown that for every 5 mmHg reduction in diastolic blood pressure, mortality decreases by 32%, stroke by 44%, diabetic complications (including amputation) by 24%, and microvascular complications (including retinal hemorrhage) by 37%. Experts have found that the lowest blood pressure group has a significantly lower incidence of cardiovascular events and the slowest rate of renal function decline. Therefore, the optimal blood pressure control target is set at 130/80 mmHg.

Treatment for hypertension is lifelong. Even when blood pressure is controlled within the ideal range, antihypertensive treatment should not be stopped to prevent potential dangerous complications.