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relaxes. Blood pressure fluctuates minute to minute, changing not only with activity and rest but also with temperature, emotions, posture, and diet. So how can we accu- rately measure it?

When a medical professional wraps a blood-pressure cuff around your arm and inflates it, the pressure in the cuff temporarily stops blood flow through your arm. When the cuff begins to deflate, gradually releasing this pressure, blood can start to flow again. The person taking your blood pres- sure listens with a stethoscope for the first full pulse of blood flow, noting the pressure at which it began. That measurement is the systolic pressure, the peak pressure created by each heartbeat. As pressure from the cuff lessens, audibility of the pulse wanes. When all pulse sounds disappear, examiners note that pressure measurement. This is diastolic pressure, the pressure on the blood vessels when the heart relaxes between beats. Blood pressure is measured in a unit called millimeters of mercury (or mm Hg), and the top number is the systolic pressure (peak pressure); the bottom number is the diastolic pressure (resting pressure). A normal or healthy blood pressure for people eighteen and over is 120/80 mm Hg or below. Borderline high blood pressure, also called pre-hypertension, is defined as 121–130 (systolic) over 81–89 (diastolic). High blood pressure (or hypertension) is diagnosed for readings of 140/90 and above. A doctor will

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