Blood pressure is the force exerted by blood against the wall of a blood vessel. It is commonly measured in a large artery with an inflatable cuff (Fig. 1) known as a blood pressure cuff or blood pressure apparatus, but technically called a sphygmomanometer. Both systolic and diastolic pressures are measured and reported as systolic then diastolic separated by a slash, such as 120/80. Pressure is expressed as millimeters of mercury (mm Hg), that is, the height to which the pressure can push a column of mercury in a tube. Blood pressure is a valuable diagnostic measurement that is easily obtained.

FIGURE 1. Blood pressure cuffs in three sizes. Shown are the cuff, the bulb for inflating the cuff, and the manometer for measuring pressure. (Reprinted with permission from Taylor C, Lillis C, LeMone P. Fundamentals of Nursing: The Art and Science of Nursing Care. 4th Ed. Philadelphia: Lippincott Williams & Wilkins, 2001. Photograph courtesy of Ken Kasper.)

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