Measurement of blood pressure at regular intervals is part of the minimum standards of monitoring during anaesthesia and sedation. Blood pressure can be measured non-invasively, either using a manual sphygmomanometer or an automated device. The basic components of a non-invasive device include a cuff with an inflatable bladder, a mechanism to inflate and deflate the cuff and a display unit. Manual sphygmomanometers are simple to use but are subject to observer bias.

In recent years, automated devices have overtaken manual sphygmomanometers. Automated devices have certain limitations with regard to their accuracy. They are unreliable in circumstances where a sudden change in blood pressure is anticipated, or where a minimal change in blood pressure is clinically relevant.