Blood pressure readings have a top number and a bottom number. The top number is the systolic blood pressure. It indicates the pressure placed on the artery walls with every heartbeat. Systolic blood pressure gets a lot of attention, but the bottom number — diastolic pressure — is important, too. Diastolic blood pressure is the pressure placed on the artery walls when the heart is resting between every heartbeat.
Medical practitioners obtain diastolic pressure readings by listening to Korotkoff sounds using a sphygmomanometer and a stethoscope. A sphygmomanometer is an inflatable cuff with a gauge. The practitioner inflates the cuff to block arterial blood flow, then listens to the brachial artery while allowing the cuff to deflate slowly. Systolic blood pressure is read at the point on the gauge where tapping sounds called Korotkoff sounds begin. Diastolic pressure is read at the point on the gauge where these sounds stop.
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