Blood pressure is the pressure of the blood on the walls of the arteries. It is measured with a sphygmomanometer, usually on the upper arm, and given in millimetres of mercury (mmHg). Two values are recorded:• systolic pressure, the highest pressure, when the ventricles contract
• diastolic pressure, the lowest pressure, when the heart relaxesA reading is written as systolic/diastolic, for example 120/80 mmHg, which is a typical healthy value.Raised blood pressure (hypertension). Hypertension is usually diagnosed when readings are consistently 140/90 mmHg or above. It often causes no symptoms, so many people do not know they have it.Worked example. A patient's blood pressure is 150/95 mmHg. The systolic value (150) is above 140 and the diastolic value (95) is above 90, so the reading indicates hypertension.Causes. Blood pressure rises when arteries are narrowed or less elastic, for example because of atherosclerosis or ageing. Factors that raise blood pressure include a diet high in salt, being overweight, lack of exercise, too much alcohol, smoking, stress and inherited factors.Why it matters. High pressure damages the endothelium of the arteries, making atherosclerosis more likely, and narrowed arteries raise the pressure further. Hypertension also makes the heart work harder, increases the risk of aneurysms rupturing and of strokes, and increases the formation of tissue fluid, which can cause oedema. It can be reduced by lifestyle changes and by drugs.
• diastolic pressure, the lowest pressure, when the heart relaxesA reading is written as systolic/diastolic, for example 120/80 mmHg, which is a typical healthy value.Raised blood pressure (hypertension). Hypertension is usually diagnosed when readings are consistently 140/90 mmHg or above. It often causes no symptoms, so many people do not know they have it.Worked example. A patient's blood pressure is 150/95 mmHg. The systolic value (150) is above 140 and the diastolic value (95) is above 90, so the reading indicates hypertension.Causes. Blood pressure rises when arteries are narrowed or less elastic, for example because of atherosclerosis or ageing. Factors that raise blood pressure include a diet high in salt, being overweight, lack of exercise, too much alcohol, smoking, stress and inherited factors.Why it matters. High pressure damages the endothelium of the arteries, making atherosclerosis more likely, and narrowed arteries raise the pressure further. Hypertension also makes the heart work harder, increases the risk of aneurysms rupturing and of strokes, and increases the formation of tissue fluid, which can cause oedema. It can be reduced by lifestyle changes and by drugs.