Blood pressure

Blood pressure (BP) is the pressure in the body's arterial system, and when measuring BP the GP or practice nurse will normally use the brachial artery in the arm.

The instrument used to measure BP is called a syphgmomanometer or "sphyg" for short, and contains a column of mercury – however, these will probably be replaced with electronic mercury-free instruments in the not-too-distant future. The measuring technique is taught to every doctor and nurse, and involves placing an inflatable cuff around the upper arm, inflating it, and letting the air out slowly whilst listening in with a stethoscope at the brachial artery.

BP is taken at the heart's level with the patient seated and as relaxed as possible. If the pressure is raised, several readings will be taken to make absolutely sure. The readings are expressed thus: 130/80 mmHg. The top figure (systolic) is the pressure in the brachial artery when the left lower chamber (the left ventricle) of the heart is contracting and pushing blood out into the aorta (the main artery transporting blood to the vital organs). The lower figure (diastolic) is the pressure when the left ventricle is relaxed and filling with blood.

High BP or hypertension is generally taken to mean a BP of more than 140/90 in an adult. Symptoms are not usually apparent, but sustained high BP is damaging and can be one of the causes of heart attacks and strokes. It can also affect the kidneys and lead to kidney failure. It may also affect the eyes, impairing sight. If your GP decides you need treatment for high BP, you must take your prescription regularly. There are numerous ways in which you can help yourself too as the articles on this site will explain.