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Millimeters of Mercury (mmHg)[edit | edit source]
Millimeters of mercury (mmHg) is a unit of pressure that is commonly used in medicine and physiology to measure blood pressure and other pressures within the body. It is also used in various scientific fields, including chemistry and physics, to measure pressure in laboratory settings.
Definition[edit | edit source]
The unit mmHg is defined as the pressure exerted by a column of mercury exactly 1 millimeter high at the standard acceleration of gravity. It is a non-SI unit of pressure, but it is still widely used in certain fields due to its historical significance and ease of use in specific applications.
Historical Context[edit | edit source]
The use of mercury in barometers and manometers dates back to the 17th century. Evangelista Torricelli, an Italian physicist, is credited with inventing the mercury barometer in 1643. The unit mmHg became a standard way to express pressure measurements in these devices.
Conversion to Other Units[edit | edit source]
1 mmHg is approximately equal to 133.322 pascals (Pa), which is the SI unit of pressure. It is also equivalent to 0.0193368 psi (pounds per square inch).
Applications in Medicine[edit | edit source]
In medicine, mmHg is most commonly used to measure blood pressure. Blood pressure readings are typically given in millimeters of mercury, with two numbers representing the systolic and diastolic pressures. For example, a normal blood pressure reading might be 120/80 mmHg.
Blood Pressure Measurement[edit | edit source]
Blood pressure is measured using a sphygmomanometer, which consists of an inflatable cuff, a measuring unit (the manometer), and a method for inflation, which may be a manually operated bulb and valve or a pump operated electrically. The pressure in the cuff is measured in mmHg.
Intraocular Pressure[edit | edit source]
In ophthalmology, mmHg is used to measure intraocular pressure (IOP), which is important in the diagnosis and management of glaucoma.
Other Medical Uses[edit | edit source]
- Intracranial Pressure (ICP): Measured in mmHg to assess conditions such as traumatic brain injury. - Central Venous Pressure (CVP): Used to assess the blood volume and venous return to the heart.
Scientific and Industrial Applications[edit | edit source]
In scientific research and industrial applications, mmHg is used to measure vacuum pressures and in the calibration of instruments.
Also see[edit | edit source]
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