Any plumber will tell you that if a pipe carries water at a pressure higher than the pressure it was designed for, it will eventually rupture. If the pressure in the pipe is not only too high but varies rapidly in its level, the rupture will occur even sooner because of the excessive stresses on the pipe. Exactly the same situation occurs in the human body when the pressure of blood in the arteries becomes too high. The arteries of a person with high blood pressure will become hardened, brittle and eventually rupture, causing a stroke, heart attack or other serious injury to vital organs.

The heart contracts regularly to pump blood through the arteries to the arms, legs, head and other organs. The blood returns to the heart along veins. When the heart contracts, the blood is moved along under high (systolic) pressure. When the heart relaxes between beats, the blood continues to flow due to the lower (diastolic) pressure exerted by the elasticity of the artery walls. When one, or both, of these pressures exceeds a safe level, the person is said to suffer from high blood pressure or hypertension.

A blood pressure reading is written by a doctor as systolic pressure/diastolic pressure (e.g. 125/70). The actual values for blood pressure vary with many things, such as exercise, anxiety, age, fitness, smoking and drinking habits, weight and medications. All these must be assessed by a doctor over several visits before the diagnosis of hypertension is made.

When a doctor is asked what a normal blood pressure should be, the answer is often evasive, because so many factors must be considered. In an elderly person, a blood pressure of 160/95 may be acceptable, but this would be considered very high in a young woman, where 110/60 would be more appropriate. Life insurance companies generally require the blood pressure to be under 136/86 for the person to be acceptable at the normal rates. The numbers are a standard measure of pressure in units of millimeters of mercury (mmHg).

There is no simple method for any individual to measure their own blood pressure, so it is a good idea to have your doctor check the pressure with a sphygmomanometer at regular intervals, particularly if you are over 40.

A sphygmomanometer works by compressing the artery in your upper arm. The cuff is inflated to a high pressure so that the artery is completely compressed and no blood can pass. The pressure is then slowly lowered until the blood can squirt past the constriction when the variable pressure is at its maximum. This squirting can be heard by a doctor through a stethoscope which is placed over the artery, just below the cuff on the inside of the elbow. As the pressure drops further, the lower pressure is eventually sufficient to keep the artery open at all times, so that the squirting through the narrowed segment that occurs at a higher pressure can no longer be heard. The doctor notes on the gauge of the sphygmomanometer the pressures at which the noise can first be heard, and when it disappears.

You can help prevent and treat hypertension by keeping your weight within reasonable limits, not eating excessive amounts of salt, not smoking, and by exercising regularly.

The majority of people with high blood pressure have no symptoms of the problem for many years, and when they do it may be too late. Up to 20% of adults over 40 years of age may have hypertension, but it can occur at any age and may be a particular problem in pregnant women. Those who do have symptoms complain of headaches and tiredness, but only when the blood pressure is very high do the further symptoms of nausea, confusion, and disturbances in vision occur.

Once diagnosed, blood tests are performed to see if there is any specific cause for the increased blood pressure, but the majority of people have 'essential' hypertension, for which there is no single identifiable cause. X-rays of the kidneys and an electrocardiograph (ECG) may also be included in the initial work-up by a doctor. The identifiable causes of hypertension include kidney disease, oestrogen- containing medications (e.g. the contraceptive pill), hyperparathyroidism, phaeochromocytoma  and a number of other rare diseases. High blood pressure may also be a complication of pregnancy, when it can lead to quite serious consequences .

A rapidly progressive condition known as malignant hypertension can sometimes develop and cause remarkably high levels of blood pressure. This requires urgent hospital treatment.

The major complications of untreated high blood pressure are strokes and heart attacks at an earlier age than would be expected with normal blood pressure. Other complications include kidney damage and bleeding into an eye.

Treatment is necessary in all cases of hypertension to prevent the serious long-term problems that may occur. There is no cure for high blood pressure, but it can be very successfully controlled in the majority of patients by taking one or two tablets a day. Some patients require higher doses of medication, but all must be continued for life, or until circumstances change (e.g. the patient is no longer obese) and enable a doctor to gradually withdraw them.

A wide range of medications are available, and some types will suit some patients better than others. It may take days or weeks for the tablets to work, and regular checks are essential until the correct dosage is determined. After that, blood pressure checks every 3 to 6 months are all that is necessary. Once controlled, there is no reason why the patient should not lead a full and active working, sporting and sexual life. Before effective treatments for blood pressure were available, most patients with moderate hypertension died within 20 years of the diagnosis. The causes of death, in order of importance, were heart disease, strokes and kidney failure.

The biggest problem facing doctors in treating patients with hypertension is that patients do not take their advice, stop the pills or fail to attend for follow-up checks. The patient who does this usually has no symptoms but is risking his or her life, because the continued excess pressure on the walls of the arteries may have fatal results.

Please Note:

• The information provided on this page is not intended as a substitute for the advice of a registered physician or other healthcare professional.

• The content of this page is intended only to provide a summary and general overview. Do not use this information to disregard medical advice, nor to delay seeking medical advice.

• Be sure to consult with your doctor for a professional diagnosis and appropriate medical treatment.