hypertension

You probably remember the routine from your last physical exam: A nurse wraps a cuff around your upper arm, pumps the cuff full of air, and then lets the air out slowly while listening through a stethoscope or watching a machine.
Most likely, you don't remember feeling anything — except perhaps that odd sensation of the blood pounding in your arm! For most guys and girls, this is the only time they think about their blood pressure.

Understanding Blood Pressure

Every person needs blood pressure to live. Without it, blood wouldn't be able to circulate through the body to carry oxygen and fuel vital organs.
Blood pressure is the pressure your blood exerts against your blood vessel walls as your heart pumps. Blood pressure rises with each heartbeat and falls when the heart relaxes between beats, but there is always a certain amount of pressure in the arteries. That blood pressure comes from two physical forces. The heart creates one force as it pumps blood into the arteries and through the circulatory system. The other force comes from the arteries resisting the blood flow.
Blood pressure changes from minute to minute and is affected not only by activity and rest, but also by temperature, diet, emotional state, posture, and medications.
Blood pressure is measured in millimeters of mercury (written as mmHg). For example, normal blood pressure in adults should be less than 120/80 mmHg. The higher, or top, number — in this example it's 120 — is called systolic pressure and represents the pressure at the peak of each heartbeat. The lower, or bottom, number (80 in this example) is called diastolic and represents the pressure when the heart is resting between beats. The systolic pressure is stated first and the diastolic pressure comes second. For example: 120/80 (120 over 80) means that the systolic pressure is 120 and the diastolic pressure is 80.
Blood pressure is measured using an instrument called a sphygmomanometer (pronounced: sfig-mow-mah-nah-meh-ter). A cuff is wrapped around a person's upper arm and pumped up to create pressure. When the cuff is inflated, it compresses (squeezes on) a large artery in the arm, stopping the blood flow for a moment. Blood pressure is measured as air is gradually let out of the cuff, which allows blood to begin to flow through the artery again when the blood pressure in the artery is greater than the pressure in the cuff.
Listening with a stethoscope — the instrument used to hear things like the heart beating inside the body — over the artery allows a doctor or nurse to hear the first pulse as the blood flows through. This is the systolic pressure. The diastolic pressure is noted when the sounds disappear.
When a machine reads out the pressure, the average blood pressure is measured and the systolic and diastolic pressures are calculated.