Blood pressure gauge
The general term used to refer to the variety of devices used to measure blood pressure. Whether the traditional mercury column, analog or digital all sphygmomanometers do essentially the same thing, measuring a person's blood pressure at the time of the test. Blood pressure varies considerably from person to person or even in the same person under differing conditions such as at rest, sitting, standing or exertion. The blood pressure results are measured with the sphygmomanometer in units of millimeters of mercury (Hg). The results are written fraction-style, such as 130/90, but are not fractional in the traditional mathematical sense. Verbally the above results would be referred to as "One thirty over ninety". The first number (called the systolic pressure) correlates the pressure exerted upon the wall of the artery being measured, usually the brachial artery near the front side of the elbow joint. This pressure is exerted by the main pumping chamber of the heart, the left ventricle. The second number (called the diastolic pressure) again correlates the pressure exerted upon the measured artery wall when the auxiliary pumping chambers (the atria) refill the ventricles.