9781422288450

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

The Silent Killer: High Blood Pressure and Heart Disease / 53