Postural hypotension

Postural (or orthostatic) hypotension is the sudden fall in blood presure that occurs when quickly changing position, for example lying down to standing or sitting to standing.

Blood pressure is the pressure of blood flowing through your blood vessels against the vessel walls. It depends on your blood flow and the resistance of your blood vessels to the blood flow. Every time the heart beats, the heart contracts and blood is pumped from the heart into the arteries and the pressure is increased (systolic phase). During the time when the heart relaxes (diastolic phase), the pressure in your blood vessels decreases. The image to the right shows the heart and blood flow during the systolic phase.

Blood pressure is measured as two numbers e.g. 120/80. The first, higher number is the pressure measured during the systolic phase. The second, lower number is the pressure during the diastolic phase. The optimal blood pressure for an adult is around 120/80mm Hg (millimetres of mercury).