Dr. Matt and Dr. Mike's Medical Podcast Medical Minutes | Why do we measure blood pressure using mercury (mmHg)?
Nov 18, 2025
Discover the fascinating world of blood pressure measurement! Delve into what systolic and diastolic pressures really mean, with insights into how our hearts create arterial pressure. Learn about the mechanics of the mercury sphygmomanometer and why mercury was chosen as the gold standard. The science behind mmHg unveils how it represents the pressure's effect on mercury. Join an engaging discussion filled with historical context and medical clarity!
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Two Values Reflect Different Forces
- Blood pressure has two values: systolic (heart contraction) and diastolic (vessel elastic recoil).
- Systolic reflects ventricular squeeze while diastolic reflects arterial elastic recoil keeping blood moving.
Historical Origin: Poiseuille's Manometer
- The mercury standard dates back to Jean-Léonard Marie Poiseuille and 19th-century physiology.
- His mercury manometer gave a practical, dense-fluid standard still used as mmHg.
Why Blood Pressure Uses mmHg
- Millimetres of mercury (mmHg) come from the 19th-century mercury manometer standard.
- The reading shows how far blood pressure would displace mercury in a tube, so 120 mmHg equals 120 mm displacement.