What is a Sphygmomanometer?

A BP monitor, commonly referred to as a blood pressure meter or blood pressure cuff, is a medical device used to measure blood pressure non-invasively. It works by using an inflatable cuff placed around the upper arm to impede blood flow through the brachial artery. The measurements are displayed and recorded in units of millimeters of mercury (mmHg).

How Does Sphygmomanometer Work?

A typical BP monitor consists of an inflatable cuff, a rubber bulb or electric pump to inflate the cuff, a release valve to deflate the cuff slowly, and a gauge to measure and display blood pressure readings. To take a blood pressure reading, the cuff is wrapped snugly around the patient's upper arm above the elbow. The cuff is then rapidly inflated using the bulb or pump until the artery is compressed. A stethoscope is placed over the brachial artery below the cuff. As the valve is released slowly to deflate the cuff, sounds called Korotkoff sounds begin to be heard through the stethoscope. The first Korotkoff sound heard represents the systolic blood pressure when the heart contracts. As the cuff continues to deflate, the sounds disappear - the reading at this point is the diastolic blood pressure when the heart rests between beats. Modern digital devices use oscillometric techniques to automate this process.

Types of BP monitors

There are different types of BP monitors used in medical settings:

- Aneroid BP monitor: Sphygmomanometer Uses a spring-activated mechanical gauge to display readings in mmHg. It is relatively inexpensive but must be calibrated regularly.

- Mercury BP monitor: Considered the gold standard but its use is being phased out due to mercury being a hazardous material.

- Digital/Electronic BP monitor: Automatically inflates the cuff and detects Korotkoff sounds electronically to display readings digitally. More accurate and convenient than manual auscultation.

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