How to recalibrate a sphygmomanometer

blood pressure image by Ivonne Wierink from

A sphygmomanometer is a device used to measure blood pressure. The two types of sphygmomanometers are aneroid and mercury. According to "Sustaining Hospitals: Comparing Mercury and Aneroid Sphygmomanometers," both models are reliable, accurate, similar in cost and relatively easy to maintain.

Both models should be calibrated frequently to ensure their measurements are accurate. Because of the dangers of mercury exposure, aneroid models tend to be more common. It is recommended that all aneroid sphygmomanometers be calibrated annually against a well-maintained mercury model.

Connect the tubing from each manometer to each side of the plastic T.

Attach the inflation bulb to the bottom of the plastic T.

Inflate the manometers using the bulb to 300mm Hg.

Release the air at a rate less than 10mm Hg per second.

Stop the release at 250, 200, 150, 100, 60 and 0mm Hg and note the reading on both manometers.

Compare the readings. If the readings are within 3mm Hg, the gauge is appropriate for clinical use. If the readings are greater than 3mm Hg apart, the manometer should be discontinued for use until corrected.