Blood Pressure

What is blood pressure?

Blood pressure, measured with a blood pressure cuff and stethoscope by a nurse or other healthcare provider, is the force of the blood pushing against the artery walls. Each time the heart beats, it pumps blood into the arteries, resulting in the highest blood pressure as the heart contracts. One cannot take his/her own blood pressure unless an electronic blood pressure monitoring device is used. Electronic blood pressure monitors may also measure the heart rate, or pulse.  

Two numbers are recorded when measuring blood pressure. The higher number, or systolic pressure, refers to the pressure inside the artery when the heart contracts and pumps blood through the body. The lower number, or diastolic pressure, refers to the pressure inside the artery when the heart is at rest and is filling with blood. Both the systolic and diastolic pressures are recorded as "mm Hg" (millimeters of mercury). This recording represents how high the mercury column is raised by the pressure of the blood.  

High blood pressure, or hypertension, directly increases the risk of coronary heart disease (heart attack) and stroke (brain attack). With high blood pressure, the arteries may have an increased resistance against the flow of blood, causing the heart to pump harder to circulate the blood.  According to the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health (NIH), high blood pressure for adults is defined as:

140 mm Hg or greater systolic pressure

and

90 mm Hg or greater diastolic pressure

In an update of NHLBI guidelines for hypertension in 2003, a new blood pressure category was added called prehypertension:

120 mm Hg – 139 mm Hg systolic pressure

and

80 mm Hg – 89 mm Hg diastolic pressure

The new NHLBI guidelines now define normal blood pressure as follows:

Less than 120 mm Hg systolic pressure

and

Less than 80 mm Hg diastolic pressure

These numbers should be used as a guide only. A single elevated blood pressure measurement is not necessarily an indication of a problem. Your physician will want to see multiple blood pressure measurements over several days or weeks before making a diagnosis of hypertension (high blood pressure) and initiating treatment. A person who normally runs a lower-than-usual blood pressure may be considered hypertensive with lower blood pressure measurements than 140/90.

Why should I monitor my blood pressure at home?

For persons with hypertension, home monitoring allows your physician to monitor how much your blood pressure changes during the day, and from day to day. This may also help your physician determine how effectively your blood pressure medication is working.

What special equipment is needed to measure blood pressure?  

Either an aneroid monitor, which has a dial gauge and is read by looking at a pointer, or a digital monitor, in which the blood pressure reading flashes on a small screen, can be used to measure blood pressure.

About the aneroid monitor: The aneroid monitor is less expensive and easier to manage than the digital monitor. The cuff is inflated by hand by squeezing a rubber bulb. Some units even have a special feature to make it easier to put the cuff on with one hand. However, the unit can be easily damaged and become less accurate. Because the person using it must listen for heartbeats with the stethoscope, it may not be appropriate for the hearing-impaired.

About the digital monitor: The digital monitor is automatic, with the measurements appearing on a small screen. Because the recordings are easy to read, this is the most popular blood pressure measuring device. It is also easier to use than the aneroid unit, and since there is no need to listen to heartbeats through the stethoscope, this is a good device for hearing-impaired patients. One disadvantage is that body movements or an irregular heart rate can change the accuracy. These units are also more expensive than the aneroid monitors.

About finger/wrist blood pressure monitors: Tests have shown that finger and/or wrist blood pressure devices are not as accurate in measuring blood pressure as other types of monitors. In addition, they are more expensive than the other monitors.

Before you measure your blood pressure:

Rest for three to five minutes without talking before taking a measurement.

Sit in a comfortable chair, with your back supported and your legs and ankles uncrossed.

Sit still and place your arm, raised level with your heart, on a table or hard surface.

Wrap the cuff smoothly and snugly around the upper part of your arm. The cuff should be sized to fit smoothly, while still allowing enough room for one fingertip to slip under it.

Be sure the bottom edge of the cuff is at least one inch above the crease in your elbow.

It is also important, when taking blood pressure readings, that you record the date and time of day you are taking the reading, as well as the systolic and diastolic measurements. This will be important information for your physician to have. 

Ask your physician or another healthcare professional to teach you how to use your blood pressure monitor correctly. 

Have the monitor routinely checked for accuracy by taking it with you to your physician's office. 

It is also important to make sure the tubing is not twisted when you store it and keep it away from heat, to prevent cracks and leaks. Proper use of your blood pressure monitor will help you and your physician in monitoring your blood pressure.