What is blood pressure

Blood pressure is necessary to supply the organs of the body with oxygen and nutriments.

In the human body the blood is found in blood vessels. They are mainly arteries and veins. The blood flowing through the blood vessels constantly exerts pressure on the vessel walls. The pressure is determined by the pumping force of the heart and the elasticity of blood vessels.

The heart generally contracts and expands again 60 - 80 times per minute on average. In doing so, it pumps the blood under pressure into the arteries in order to supply the organs of the body with oxygen and nutriments. The blood vessels branch out more and more until they become capillary blood vessels (capillaries). This 'plumbing system' offers more or less resistance to the bloodstream, if it is under enough pressure.

The pressure is highest at the moment of the heartbeat, that is when the heart is contracting. This pressure is known as the systolic blood pressure. The contraction phase of the heart in which the blood pressure rises is known as the systole. The blood pressure is at its lowest between two heartbeats, i.e. when the heart muscle relaxes. The blood pressure at this point is referred to as the diastolic blood pressure. The phase in which the heart relaxes and the blood pressure decreases is known as the diastole.

Blood pressure is measured in mmHg. The systolic value is always stated first, then the diastolic value. For example: 120/80 mmHg means that the systolic blood pressure is 120 mmHg and the diastolic blood pressure is 80 mmHg.1 mmHg is the pressure that one millimetre (mm) of mercury (Hg) exerts. As a conversion: 1 mmHg = 0.00133 bar.