Gaining control of blood pressure begins with understanding what constitutes normal blood pressure and what is high blood pressure. Armed with this knowledge, you can take appropriate steps to bring your blood pressure back to normal.

The body is a marvelous system that is both complex and wonder- fully simple. It consists of about fifteen trillion cells, which are grouped into tissues and organs. These organs are further organized into systems. Each cell, organ, and organ system has a specific purpose.

The organs involved in blood pressure include the skin, heart, lungs, kidneys, and some glands. The systems involved are the cardiovascular and excretory systems. Most tissues, especially the muscle and vascular tissues, are also critically involved.

Each individual cell requires many nutrients, with oxygen being the most important. As nutrients are metabolized, waste products, the most abundant of which is carbon dioxide, accumulate and must be removed.

The cardiovascular system, a specialized complex organ system, is responsible for the distribution of nutrients and the removal of wastes from each cell.

The heart pumps bright red, oxygen-laden blood into the largest artery, the aorta, which branches into smaller and smaller arteries called arterioles and capillaries. Arterioles and microscopic capillaries infiltrate every tissue, carrying oxygen and other nutrients to each cell.

The venous system then carries waste-laden blood to the lungs to remove carbon dioxide and to the kidneys to remove other wastes. The cleansed blood returns to the heart and is then pumped out for another voyage through the system.

The arterioles and veins that bring blood to and from the muscles and skin constitute the peripheral circulatory system. Besides bringing nutrients to the cells and removing wastes, this system is essential in regulating body temperature.

Peripheral blood flow regulates temperature by either increasing blood flow to the surface to radiate heat into the environment or restricting blood flow to conserve heat. During exercise, for example, blood flow is increased not only to meet nutrient demands of the tissues but also to radiate heat.

Conversely, in a cold environment, blood flow to the surface is reduced to conserve body temperature. Since the heart’s job is to pump blood, it is easy to understand why pressure is essential. Like any other fluid pump, the heart pushes the blood around with a force we call blood pressure.

Because the heart pushes the blood into the arterial system on a single stroke, two pressures are important: the systolic or higher pressure is the force generated when the blood is pushed into the arteries; the diastolic or lower pressure remains in the system when the heart’s pumping chamber, the left ventricle, relaxes to fill again with blood as it gets ready for the next push.

Normal adult blood pressure, on average, is 120 systolic and 80 or less diastolic, simply expressed as 120 over 80. Individually, the numbers correspond to millimeters of mercury, but when expressed as a fraction, such as 120/80, the figures have no absolute value and are simply relative.

Although blood pressure is no longer measured against a column of mercury measured in millimeters, a mercury column is used to calibrate the instruments, so the unit remains meaningful, and some physicians still use these devices.

Normal blood pressure is that of an average, healthy individual of a particular age group. It can vary rather widely; for example, my blood pressure is usually 110 over 70 or less, and sometimes it is as low as 100/60. On occasion, when I’m very nervous or active, it soars to 130/90.

A rule of thumb teaches that systolic should be 100 plus your age, up to age twenty, and diastolic should be 40 less than systolic. So, for our purposes, normal is 120/80, and recognize that a little higher or lower is still within safe bounds.

How Blood Pressure Develops?

Blood pressure is the amount of blood pumped, the rate of pumping, and the resistance that it must overcome. In medical terminology, we say that blood pressure is the product of cardiac output and total peripheral resistance. It follows that there are two major determinants of blood pressure: heart output and the factors that restrict blood flow.

Heart (Cardiac) Output - Cardiac output is the result of stroke volume, or the amount of blood expelled by each contraction of the pumping chamber, multiplied by the actual number of beats per minute.

Total Peripheral Resistance - Once blood is pumped from the heart, the resistance to flow is determined by three factors: the flowability or viscosity of the blood, the elasticity or flexibility of the venous and arterial systems, and the number and diameter of the arterioles.

Blood viscosity describes blood’s ability to flow. Viscosity means the resistance of liquid to flow. For example, honey has a high viscosity; it doesn’t flow easily. By contrast, water has a low viscosity. Blood with low viscosity flows more easily than that with high viscosity.

The elasticity of the arterial and veinal walls describes their ability to stretch. They can be like a set of rigid pipes or flexible and stretchable like a rubber hose that handles surges in water pressure by giving and relaxing.

Neither the arterial nor the venous systems are meant to be rigid conduits. On the contrary, each should be flexible and capable of distending and contracting. The less rigid the arteries, the lower the blood pressure will be.

Likewise, by distending or contracting, the venous system be- comes a dynamic reservoir that can determine how much blood from each stroke is returned to the heart. If the venous system is rigid and constricted, the return volume will be large.

Consequently, each stroke must expel a large volume, which can elevate blood pres- sure because the heart has a larger task to perform. Diameter and abundance of the arterioles is the third and usually the most dominant factor that determines blood pressure.

The arterioles that bring blood to the muscles and skin make up the peripheral blood flow. The more dilated the arterioles and the more flexible the venous system, the lower the blood pressure will be.

Total peripheral resistance consists of the viscosity of the blood, the elasticity of the arteries and veins, and the number, size, and state of the arterioles. All three factors contribute to blood pressure. If viscosity is high, the arterial and venous systems are rigid, and arterioles are few and small, blood pressure will be higher.

Therefore, by reducing blood viscosity, increasing the number and size of the arterioles, and causing arteries to relax, blood pressure can be reduced because the total peripheral resistance will be less. This can be accomplished by the effective use of exercise and lifestyle changes.

How High is Too High?

In 1913, a father-and-son team of physicians, the Janeways, reported that about 11 percent of their patients had systolic blood pressure over 165 millimeters of mercury.

Significantly, they also noted that these patients didn’t live as long as those whose systolic pressure was not so high. It is now accepted by all health agencies worldwide that the more elevated the blood pressure.

The greater the risk of an early death from a variety of illnesses, ranging from heart attack and stroke to kidney failure. It’s important to diagnose the presence of high blood pressure early and to deal with it effectively.

In 1984, the National Committee on High Blood Pressure published its conclusions in the Archives of Internal Medicine and established a classification system for blood pressure.

Category of Hypertension	Range in Millimeters of Mercury Diastolic BP
Normal blood pressure	Less than 85
High normal	85 to 89
Mild hypertension	90 to 104
Moderate hypertension	105 to 114
Severe hypertension	115 or higher
	Systolic BP When Diastolic BP Is Less Than 90
Normal	Less than 140
Borderline isolated systolic hypertension	140 to 159
Isolated systolic hypertension	160 or more

Blood pressure doesn’t go from normal to severe hypertension overnight; it creeps up slowly. Diastolic pressure over 80 millimeters of mercury is a warning sign that diet and lifestyle should change.

Insurance companies consider high blood pressure when selling a life insurance policy, an indication of its seriousness. Less than 10 percent of high blood pressure cases are the result of a specific problem, such as kidney disease, an adrenal tumor, or constriction of the major artery (the aorta).

When such a cause is identified, this condition is called secondary hypertension, because it is the by-product of another illness. When that illness is corrected, the hypertension usually disappears.

Common high blood pressure, which accounts for over 90 percent of all high blood pressure cases, is called essential hypertension. It is usually the result of many factors combined, including heredity, excess weight, poor diet, and lack of fitness, to name the most common.

Symptom of the Silent Killer

High blood pressure is called the silent killer because many people with the problem never know they have it. Of the fifty million Americans with high blood pressure, only about thirty million have been diagnosed.

The rest may never know until they go to a doctor for another reason—a physical for insurance purposes, a stroke, heart attack, kidney failure, or some other problem either caused by or having nothing to do with high blood pressure—and have their blood pressure taken in a workup.

If your diastolic blood pressure went from 70 one day to 105 the next, you’d immediately get symptoms. But blood pressure usually creeps up slowly, often over many years, and your body adjusts to the gradual change.

You feel “normal” until that day your doctor or the nurse says, “Your blood pressure’s too high!” However, you may experience the following symptoms, which can be early warning signs of high blood pressure.

• Headaches, especially in the morning
• Ringing in the ears
• Unexplained dizziness
• Spontaneous nosebleeds
• Depression without apparent cause
• Blurred vision
• Tension when there is no cause
• Flushing of the face
• Fainting spells

Causes of High Blood Pressure

Seldom is high blood pressure the result of only one problem. Indeed, most common high blood pressure is the outcome of many factors that have accumulated over the years. Following is a list of common causes.

• Alcohol
• Dietary fat imbalance
• Low dietary K-factor (sodium-potassium balance); excess sodium chloride (salt)
• Excess weight
• Heredity
• Insulin overload
• Poor nutrition
• Poor fitness
• Stress
• Type A personality traits

About 85 percent of all high blood pressure cases can be reversed by deliberate changes in diet and lifestyle. About two-thirds of the remaining 15 percent can significantly bring down their need for medication by the same measures.

This means that nearly everyone with high blood pressure can dramatically lower his blood pressure by actions he takes.