Illustration of blood pressure measurement
Blood pressure is a measurement of the pressure that blood exerts against the walls of the main arteries and is quoted in millimeters of mercury (mmHg). Measurements are made when the heart is contracting (the systolic pressure) and during relaxation (the diastolic pressure); results are presented as the systolic over the diastolic pressure. A typical value for a normal, young adult might be 120/80 mmHg. Here, a massive systolic pressure of 240mmHg is displayed on the sphygmomanometer. Abnormally high blood pressure (hypertension) is a serious medical condition with a variety of underlying causes.
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. The upper arm should be bare, with your sleeve comfortably rolled up. 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 pulse and will place the head of the stethoscope over this artery, below the cuff. It should not rub the cuff or any clothing because these noises may block out the pulse sounds. Correct positioning of the stethoscope is important to get an accurate recording. 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 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 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). The procedure may be performed two or more times. Most people cannot sense if their blood pressure is high (hypertension) because there are usually no symptoms. High blood pressure increases the risk of heart failure, heart attack, stroke, and kidney failure. For people who have high blood pressure, this test is a way of monitoring the effectiveness of medications and dietary modifications. The systolic pressure less than 120 mmHg and the diastolic pressure less than 80 mmHg blood pressure is considered normal. Blood pressure that is slightly higher than 140/90 is called mild mild hypertension and can sometimes be reduced by weight loss, cessation of smoking, and decreased salt intake. Systolic blood pressure lower than 90 or pressure 25 mmHg lower than usual reading is considered low blood pressure. Low blood pressure may be a sign of a variety of illnesses, including heart failure, infection, gland disorders, and dehydration.