Blood pressure is the force of blood inside an artery. A blood
pressure reading measures the force of blood against the walls of an
Blood pressure is measured by temporarily stopping the flow of
blood in an artery, usually by wrapping a cuff around the upper arm and pumping
air into the cuff. As the air is released from the cuff, blood begins to flow
through the artery again. When the blood begins to flow, the sound of blood
flowing through the artery can be heard through a stethoscope placed on the
skin over the artery inside the elbow.
Blood pressure readings consist of an upper and
lower number (such as 120 over 90 or 120/90). Blood pressure readings are
measured in units called millimeters of mercury (mm Hg).
reading on the gauge when blood flow is first heard is called the
systolic pressure. It is the first or upper number in a
blood pressure reading. Systolic pressure is the pressure of blood against the
artery walls when the heart has just finished contracting or
The reading on the gauge when blood flow is no longer
heard is the diastolic pressure. It is the second or
lower number in a blood pressure reading. Diastolic pressure is the pressure of
blood against the artery walls between heartbeats, when the heart is relaxed
and filling with blood.
Blood pressure readings usually increase as
a person ages and with a variety of medical conditions.
E. Gregory Thompson, MD - Internal Medicine & Robert A. Kloner, MD, PhD - Cardiology
How this information was developed to help you make better health decisions.