How is Blood Pressure Measured?

1. The most common blood pressure measurement tool is a cuff that is wrapped around your upper arm. A tube attaches the cuff to a reservoir of mercury at the bottom of a vertical glass tube.

Using a rubber bulb, your health care practitioner blows air into the cuff, making it tight around your arm. This pressure moves the mercury in the column--up with a heart beat and down when the heart is resting between beats.

While watching the level of mercury, the practitioner uses a stethoscope to listen to your pulse while the air is being released.

Blood pressure measurements are shown as two numbers and measured in levels of mercury, for example: 120/80mmHg
The first number (120) is systolic pressure, measured when the pulse is first heard.

The second number (80) is diastolic or resting pressure, when the pulse is no longer heard and the mercury level drops.

2. Electronic measuring devices are becoming more common because mercury is now considered a hazardous substance.

Electronic devises can eliminate some of the human error that can occur using a blood pressure cuff and a stethoscope.

3. With ambulatory blood pressure monitoring, you wear a device that measures your blood pressure during a 24 period.

Your blood pressure readings are recorded, providing a detailed report of how your blood pressure varies during a normal day, including sleep.

This method is useful for patients who get nervous during medical appointments, which creates a higher than normal blood pressure reading.