Blood pressure measurement. Man's wrist wearing a portable digital sphygmomanometer displaying his blood pressure. An inflatable cuff (grey) is around the wrist and is connected to a digital electronic device. The cuff is inflated exerting pressure which stops blood flow in the arm. The pressure is released, and the separate systolic (127) and diastolic (82) pressures of the pumping and relaxed heart are displayed. Blood pressure is expressed in millimetres of mercury (mm Hg). Although fluctuating over the day, blood pressure is an important measure of bodily health. This machine can also measure resting pulse rate. (See M390/259 for this machine displaying pulse rate.)