A sphygmomanometer is the device for measuring blood pressure, the familiar inflatable cuff of the doctor’s surgery. The cuff wraps the upper arm and inflates to occlude the brachial artery, then deflates slowly while the clinician listens with a stethoscope for the Korotkoff sounds that mark systolic and diastolic pressure, or while an electronic sensor detects them automatically. The reading, in millimetres of mercury, is the most basic cardiovascular vital sign, guiding the diagnosis and management of hypertension. In nutrition, blood pressure is the outcome that salt-reduction and weight-loss interventions aim to move. The device’s name is famously unpronounceable, but its function is simple: squeeze, listen, read.