Medical Definition of mm Hg
: a unit of pressure equal to the pressure exerted by a column of mercury 1 millimeter high at 0°C and under the acceleration of gravity and nearly equivalent to 1 torr (about 133.3 pascals) <The pulse was 110 beats per minute and the blood pressure was 105/60 millimeter Hg …—Michael Drancourt et al., The New England Journal of Medicine, 16 Feb. 1995> <34% of treated eyes had only a transient rise in intraocular pressure of 5 millimeter Hg or more …—David Frankel, The Lancet, 27 Dec. 1995>
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