What is a sphygmomanometer?

While sphygmo could be a problem, the manometer part should easily indicate that this has something to do with pressure. Sphygmo is based on a Greek word for pulse.

Dating back to 1881, this blood pressure measuring instrument initially used a mercury column or manometer to indicate a person’s pulse in millimeters of mercury. However, it wasn’t until 1896 that a cuff was added to apply pressure to the upper arm. Measuring the pressure difference between systolic blood pressure and diastolic blood pressure of the pulse by hearing the Korotkoff sounds within the arteries by using a stethoscope was the final piece of the blood pressure measurement process. It was added in 1905.

Systolic blood pressure is the level in blood vessels when the heart beats. In contrast, diastolic blood pressure is the level when the heart rests between beats. The two measurements are typically expressed as a systolic value over the diastolic value, with a 120 over 80 or 120/80 mmHg reading being the normal value. Readings above 140/90 Hg indicate high blood pressure where the person needs to take steps to reduce that value.

The use of aneroid gauges that have a metallic pressure sensing element instead of the mercury fluid (aneroid means without fluid), provided an alternative measuring technique.

After making blood pressure measurements for over 100 years, silicon-based microelectromechanical systems (MEMS) pressure sensors with additional electronic circuitry helped the sphygmomanometer become an automatic measuring device with pumps and valves to apply and release the pressure and a digital display to capture the readings. However, both the mercury manometer and aneroid gauges are still commonly used for sphygmomanometers, especially in professional medical applications.