Traditionally, systemic arterial blood pressure is estimated using a stethoscope and a blood pressure cuff connected to a mercury column or other sphygmomanometer (Figure 2). The cuff is placed on the upper arm and inflated to stop arterial blood flow to the arm from the brachial artery; the high pressure in the cuff causes the artery to collapse in the cuff is then released slowly. When the systolic pressure in the artery exceeds the cuff pressure, blood slowly flows to the arm through the partially collapsed artery. Because the flow is through a partially occluded vessel, the flow instead of being laminar is turbulent. And therefore this flow can be heard through the stethoscope. These sharp, tapping sounds are called Korotkoff sounds. When Korotkoff sounds are first heard, the cuff pressure approximates systolic pressure. As cuff pressure is reduced further, the sounds heard through the stethoscope increase in intensity and then suddenly become muffled. The cuff pressure at the point of sound muffling approximates diastolic blood pressure.