Blood pressure represents the force exerted by circulating blood against the walls of the body’s arteries. These arteries are the vessels responsible for carrying blood away from the heart. Understanding blood pressure provides insights into cardiovascular function and overall health, with healthy levels contributing to proper bodily function.
Millimeters of Mercury (mmHg): The Standard Unit
Blood pressure is universally measured in millimeters of mercury (mmHg). The use of mercury historically stems from early blood pressure devices, known as mercury manometers, which used a column of mercury to indicate pressure levels. Even with modern digital devices, mmHg remains the established standard for reporting readings, serving as a consistent metric across medical contexts.
Understanding Systolic and Diastolic Readings
A blood pressure reading consists of two numbers, typically presented as a fraction (e.g., 120/80 mmHg). The first, or top, number is the systolic pressure. This measurement indicates the pressure within the arteries when the heart contracts and pumps blood out into the circulatory system. The second, or bottom, number is the diastolic pressure. This represents the arterial pressure when the heart rests and refills with blood between beats.
Both numbers provide distinct information about heart function and arterial health. The systolic reading reflects the force generated during the heart’s active pumping phase. The diastolic reading, conversely, shows the resting pressure in the arteries, indicating how well the vessels relax. An ideal blood pressure for most adults is below 120/80 mmHg. Deviations from these ranges can indicate health concerns, emphasizing the need for monitoring.
The Measurement Process
Blood pressure measurement involves a device called a sphygmomanometer, commonly known as a blood pressure cuff. This cuff is wrapped around the upper arm, positioned above the elbow. The cuff then inflates, temporarily compressing the brachial artery and briefly stopping blood flow. As the air is slowly released from the cuff, a healthcare professional or the automated device detects the return of blood flow.
The first sound of blood pulsing as pressure is released corresponds to the systolic pressure. As the cuff continues to deflate, the sounds eventually disappear, which marks the diastolic pressure. The device then displays these two values, providing the blood pressure in mmHg. This method allows for a standardized assessment of arterial pressure.