Final answer:
Blood pressure measured with a sphygmomanometer is the pressure above atmospheric pressure. The device includes an inflatable cuff and a manometer, and it provides readings in millimeters of mercury (mm Hg).
Step-by-step explanation:
The measurement of blood pressure using a sphygmomanometer indeed measures the pressure above atmospheric pressure. This medical device consists of an inflatable cuff, a manometer, and usually a stethoscope for manual models. The cuff is placed around the upper arm and inflated to restrict blood flow. When inflated to beyond systolic pressure, blood flow in the artery is temporarily stopped. The pressure is then slowly released until blood flow resumes, which represents the systolic pressure. As the cuff's pressure decreases further and the sound of blood flow dissipates, the diastolic pressure is determined. Units of measurement for blood pressure are in millimeters of mercury (mm Hg), indicating the pressure exerted within the manometer above the existing atmospheric pressure.