Blood pressure is the pressure that blood pumped by the heart exerts against the walls of the arteries. The amount of pressure depends upon the strength and rate of the heart’s contraction, the volume of blood in the circulatory system, and the elasticity of the arteries.
Loading the player...Blood pressure
Blood pressure is measured with an instrument called a sphygmomanometer << `sfihg` moh muh NAHM uh tuhr >> . This instrument consists of (1) a cuff or wide rubber band that can be filled with air; (2) a hollow rubber bulb, which pumps air into the cuff; and (3) a gauge to measure pressure. To take blood pressure, a physician or nurse wraps the cuff around the patient’s upper arm. A stethoscope is placed over the arteries of the arm just below the cuff. As air is pumped into the cuff, it presses down on the arteries, disrupting blood flow. This action creates a distinct sound that can be heard through the stethoscope. When the cuff is inflated to a certain point, it cuts off blood flow and the sound stops. The air is then slowly let out of the cuff. When the pressure in the cuff is less than the blood pressure, blood flow returns, and sound is heard. The pressure at which the flow of blood resumes and sound is first heard is called systolic pressure. It represents the blood pressure when the heart is contracting. As more air is let out, the sound becomes muffled, and then disappears. The pressure at this point is the diastolic pressure. It represents the blood pressure when the heart is relaxing.
Measurements of blood pressure include two numbers, such as 120/80. The first number refers to the systolic pressure, and the second number refers to the diastolic pressure. Normal systolic blood pressure for adults is below 120, and normal diastolic is below 80. Diastolic blood pressure between 80 and 89 is considered prehypertension, and blood pressures greater than 140 systolic and 90 diastolic are considered hypertension (high blood pressure). Among people at risk of heart disease, doctors consider blood pressure above 130/80 to be hypertension.
Blood pressure usually rises with age as blood vessels become less elastic and more rigid. Hypertension may cause heart failure, stroke, or kidney failure. Physicians call high blood pressure essential hypertension when the cause is unknown. When it is caused by other illnesses, such as chronic kidney failure, high blood pressure is called secondary hypertension.
Physicians treating hypertension begin with an examination of the patient’s medical history, physical examination, and various laboratory tests. In many patients, restricting the amount of sodium in the diet, losing weight, avoiding alcohol, and exercising regularly are sufficient to lower blood pressure. In others, medications are necessary to control hypertension. Diuretics—that is, drugs that increase the production of urine—are often the first choice. These drugs work by increasing the kidneys’ ability to eliminate sodium. Beta-blockers reduce the rate and force of the heartbeat and thereby lower blood pressure. ACE inhibitors and angiotensin receptor blockers (ARB’s) reduce blood pressure by blocking the action of angiotensin, a chemical that narrows blood vessels. Calcium channel blockers also reduce blood pressure by expanding blood vessels throughout the body.
