A sphygmomanometer is a medical instrument designed to measure arterial blood pressure, a fundamental indicator of cardiovascular health. Also known as a blood pressure monitor, this device plays a significant role in routine health assessments and managing conditions affecting blood circulation. It provides valuable insights into the heart’s pumping efficiency and the elasticity of blood vessels.
Components of a Sphygmomanometer
A sphygmomanometer consists of several parts that work together to measure blood pressure. The inflatable cuff, containing an internal bladder, wraps around the upper arm to apply pressure to the brachial artery. This bladder inflates with air, compressing the artery to temporarily stop blood flow.
Air is pumped into the cuff using a rubber bulb, and a control valve allows for the gradual release of this air. A manometer, either an aneroid gauge or a mercury column, measures the pressure within the cuff. For manual measurements, a stethoscope is also used to listen for specific sounds produced by blood flow.
How a Sphygmomanometer Measures Blood Pressure
Measuring blood pressure involves placing the inflatable cuff around the upper arm. The cuff is inflated rapidly until the pressure exceeds the arterial pressure, temporarily stopping blood flow in the brachial artery. At this point, no sounds are heard through a stethoscope placed over the artery.
The air is then slowly released from the cuff, allowing the pressure to drop gradually. As the cuff pressure falls, blood begins to flow turbulently through the partially constricted artery, creating distinct sounds known as Korotkoff sounds. The pressure reading on the manometer when the first tapping sound is heard indicates the systolic blood pressure. As deflation continues, the sounds change and eventually disappear entirely. The point at which these sounds vanish marks the diastolic blood pressure, indicating the pressure when blood flow through the artery becomes smooth and unobstructed again.
Interpreting Blood Pressure Readings
Blood pressure readings are presented as two numbers, written as systolic over diastolic, measured in millimeters of mercury (mmHg). The first number, systolic pressure, represents the force against artery walls when the heart contracts and pumps blood out. The second number, diastolic pressure, reflects the pressure in the arteries when the heart rests and refills with blood between beats. Both numbers provide important information about heart function and arterial health.
For most adults, a healthy blood pressure is considered less than 120 mmHg systolic and less than 80 mmHg diastolic. Readings between 120-129 mmHg systolic and less than 80 mmHg diastolic are categorized as elevated. If the systolic pressure is consistently 130 mmHg or higher, or the diastolic pressure is 80 mmHg or higher, it may indicate high blood pressure, also known as hypertension. Regular monitoring of blood pressure is important because sustained high readings can increase the likelihood of serious health issues.