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Blood
pressure is measured using a medical instrument called a
sphygmomanometer. A rubber cuff is wrapped around your upper arm and
inflated. When the cuff is inflated, it compresses a large artery
in your arm, momentarily stopping the blood flow.
Next, air in the cuff is
released, and the person measuring the blood pressure listens with a
stethoscope. When the blood starts to pulse through the artery, it
makes a sound. Sounds continue to be heard until pressure in the
artery exceeds the pressure in the cuff.
The person listens and
watches the gauge, then records two measurements. Systolic
pressure is the pressure of the blood flow when the heart beats (the
pressure when the first sound is heard). Diastolic pressure is the
pressure between heartbeats (the pressure when the last sound is
heard). Blood pressure is measured in millimeters of mercury, which
is abbreviated mm Hg.
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