What is the primary physical characteristic measured by a sphygmomanometer?

A sphygmomanometer is specifically designed to measure blood pressure, which is a critical aspect of assessing cardiovascular health. This instrument typically consists of an inflatable cuff that is placed around the arm, along with a gauge that displays the pressure readings in millimeters of mercury (mmHg).

When used, the cuff inflates to constrict the blood flow in the artery, and as the pressure is released, the device measures the pressure at which blood begins to flow again (systolic pressure) and when it can flow freely (diastolic pressure). These readings provide essential information about the state of the cardiovascular system, helping to identify conditions such as hypertension or hypotension.

The other options, while vital signs that indicate different aspects of health, are not measured by a sphygmomanometer. Heart rate is determined by counting pulse beats, body temperature is assessed with a thermometer, and respiratory rate requires observing breaths taken over a period of time. These measurements, although important, do not pertain to the primary function of a sphygmomanometer, which is solely focused on assessing blood pressure.