Measuring blood pressure. A hollow cuff attached to a pressure gauge is wrapped around the upper arm. Then it is inflated witih air to a pressure above the highest pressure of the cardiac cycle (at systole, when the ventricles contract). Above this pressure, no sounds are heard through a stethoscope positioned above the artery (because no blood is flowing through it.)
Air in the cuff is slowly released. So some blood flows into the artery. The turbulent flow causes soft tapping sounds, and when this first occurs, the value on the gauge is the systolic pressure-about 120 mm mercury (Hg) in young adults at rest. (This means the measured pressure would force mercury to move upward 120 millimeters in a narrow glass column.) more air is released from the cuff. Just after the sounds become dull and muffled, blood flow continuously. So the turbulence and tapping sounds stop. The silence corresponds to the diastolic pressure (at the end of a cardiac cycle, just before the head pumps out blood). Generally the reading is about 80 mm Hg. In this example, the pulse pressure (the difference between the highest and lowest pressure readings) is 120-80, or 40 mm Hg.
Air in the cuff is slowly released. So some blood flows into the artery. The turbulent flow causes soft tapping sounds, and when this first occurs, the value on the gauge is the systolic pressure-about 120 mm mercury (Hg) in young adults at rest. (This means the measured pressure would force mercury to move upward 120 millimeters in a narrow glass column.) more air is released from the cuff. Just after the sounds become dull and muffled, blood flow continuously. So the turbulence and tapping sounds stop. The silence corresponds to the diastolic pressure (at the end of a cardiac cycle, just before the head pumps out blood). Generally the reading is about 80 mm Hg. In this example, the pulse pressure (the difference between the highest and lowest pressure readings) is 120-80, or 40 mm Hg.
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