What is the common unit of measure for blood pressure?

Blood pressure is commonly measured in millimeters of mercury (mmHg), which is a unit that originated from the historical use of mercury columns in barometers and sphygmomanometers. This measurement indicates how high the mercury rises in a column due to the pressure exerted by the blood against the walls of the arteries.

Using mmHg is particularly significant in medical contexts because it provides a consistent and easily interpretable scale for the levels of pressure in the cardiovascular system. The readings often consist of two numbers: the systolic pressure (the pressure during the heart's contraction) over the diastolic pressure (the pressure when the heart is at rest), for example, 120/80 mmHg.

Other options, such as Pascals, atmospheres, and bars, while they do measure pressure, are not commonly used in clinical practice for blood pressure. Instead, they are more relevant in other scientific contexts, such as physics or engineering, and would not provide the familiar context needed for understanding blood pressure readings in a health care setting. Thus, the use of mmHg remains the standard for recording and communicating blood pressure in medicine.