millimetre of mercury 

https://doi.org/10.1351/goldbook.M03927
Non-SI unit for pressure; mmHg≈133.322 Pa. This old unit is not recognized by CIPM or ISO, but it is used for blood pressure.
Source:
PAC, 1996, 68, 957. (Glossary of terms in quantities and units in Clinical Chemistry (IUPAC-IFCC Recommendations 1996)) on page 981 [Terms] [Paper]
Citation: 'millimetre of mercury' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.M03927 RIS BibTex EndNote
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Last revised: February 24, 2014