Blood pressure is a measurement of the force applied to the walls of the arteries as the heart pumps blood through the body. The pressure is determined by the force and amount of blood pumped, and the size and flexibility of the arteries.
Blood pressure is continually changing depending on activity, temperature, diet, emotional state, posture, physical state, and medication use.
Diastolic blood pressure; Systolic blood pressure
How the test is performed
Blood pressure is usually measured while you are seated with your arm resting on a table. Your arm should be slightly bent so that it is at the same level as your heart. Your upper arm should be bare, with your sleeve comfortably rolled up.
Blood pressure readings are measured in millimeters of mercury (mmHg) and are given as two numbers. For example, 110 over 70 (written as 110/70).
- The top number is the systolic blood pressure reading. It represents the maximum pressure exerted when the heart contracts.
- The bottom number is the diastolic blood pressure reading. It represents the minimum pressure in the arteries when the heart is at rest.
To obtain your blood pressure measurement, your health care provider will wrap the blood pressure cuff snugly around your upper arm, positioning it so that the lower edge of the cuff is 1 inch above the bend of the elbow.
The health care provider will locate the large artery on the inside of the elbow by feeling for the
Your health care provider will close the valve on the rubber inflating bulb and then will squeeze it rapidly to inflate the cuff until the dial or column of mercury reads 30 mmHg higher than the usual systolic pressure. If the usual systolic pressure is unknown, the cuff is inflated to about 210 mmHg.
Next, the valve is opened slightly, allowing the pressure to fall gradually (2 to 3 mmHg per second). As the pressure falls, the level on the dial or mercury tube at which the sound of blood pulsing is first heard is recorded. This is the systolic pressure.
As the air continues to be let out, the sounds will disappear. The point at which the sound disappears is recorded. This is the diastolic pressure (the lowest amount of pressure in the arteries as the heart rests).
Review Date: 05/23/2010
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.