Home blood pressure testing

HOME BLOOD PRESSURE MONITORING

Test Overview

Blood pressure is a measure of the force of blood inside an artery. If your blood pressure is higher than normal on two or more occasions after an initial screening, you may have high blood pressure (hypertension). A blood pressure measurement is taken by temporarily stopping the flow of blood in an artery (usually by inflating a cuff around the upper arm) and then listening for the sound of the blood beginning to flow through the artery again as air is released from the cuff.

As blood flows through the artery, it can be heard through a stethoscope placed on the skin over the artery inside the elbow. Blood pressure is recorded as two measurements.

• The reading on the gauge when blood flow is first heard is called systolic pressure
• Systolic pressure represents the peak blood pressure that occurs when the heart contracts.
• The reading on the gauge when blood flow can no longer be heard is the diastolic pressure
• Diastolic pressure represents the lowest blood pressure that occurs when the heart relaxes between beats.

These two pressures are expressed in millimeters of mercury (mm Hg) because the original devices that measured blood pressure used a column of mercury. Systolic pressure, the higher of the two readings, is measured first. Diastolic pressure is the lower reading. These blood pressure measurements are recorded as systolic/diastolic. For example, if your systolic pressure is 120 mm Hg and your diastolic pressure is 80 mm Hg, your blood pressure is recorded as 120/80 and read as "120 over 80."

High blood pressure is defined as a systolic blood pressure of 140 mm Hg or higher or a diastolic blood pressure or 90 mm Hg or higher. High blood pressure means that the heart must work harder to pump blood throughout the body. Uncontrolled high blood pressure increases the risk of stroke, heart failure, kidney failure, and heart attack. As blood pressure increases, the risk of it causing these problems also increases.

High blood pressure is often referred to as the "silent killer," because it usually has no obvious symptoms and most people cannot tell if their own blood pressure is high unless it is measured.

Home blood pressure monitors make it easy to measure your blood pressure at home. If you are concerned that you might have high blood pressure, or if your family has a history of high blood pressure, you may want to consider getting a home blood pressure monitor.

The two general types of blood pressure monitors commonly available are manual and automatic. (Automatic types may also be called electronic or digital).

MANUAL BLOOD PRESSURE MONITORS

Manual models are similar to those that your doctor or nurse might use to take your blood pressure. Called a sphygmomanometer, these devices usually include an arm cuff, a squeeze bulb for inflation, a stethoscope or microphone, and a mechanical gauge or column of mercury to measure the blood pressure. Manual blood pressure monitors require good eyesight and hearing to use them correctly. There are two basic styles of manual blood pressure devices.

• Mercury column blood pressure devices A column of mercury rises and falls in a clear tube with the units of measure marked along the side. As the cuff pressure increases, the mercury rises. As the cuff pressure falls, so does the mercury column. A stethoscope is required to listen for the sound of blood flowing through the artery. Mercury column blood pressure monitors are the most accurate of the blood pressure devices, but they are bulky, easily broken, and may be difficult to read. It takes practice to learn to use them properly.
• Aneroid blood pressure devices These display the blood pressure on a circular dial with a needle. As the pressure in the cuff rises, the needle moves clockwise on the dial. As the cuff pressure falls, the needle moves counterclockwise. Again, a stethoscope is required; some models have the stethoscope head permanently attached to the cuff. The aneroid devices are compact and inexpensive but somewhat difficult to use. Also, the dial gauges may need to be recalibrated from time to time to maintain their accuracy.

Automatic (also called electronic or digital) blood pressure monitors

Electronic battery-operated monitors use a microphone to detect blood pulsing in the artery instead of having to listen with a stethoscope. The cuff, which is attached to your wrist or upper arm, is connected to an electronic monitor that automatically inflates and deflates the cuff when you press the start button. First you place your wrist or upper arm inside the cuff. Then press the start button on the monitor and wait for a reading to display. The monitor records your pulse as well as your blood pressure.

The electronic devices are by far the easiest to use, but they are also the most expensive. Generally, the electronic models that use an arm cuff are more accurate than those that use a wrist cuff.

The type of blood pressure monitor typically found in supermarkets, pharmacies, and shopping malls is an electronic device.

Ambulatory blood pressure monitoring (ABPM)

Another method of measuring blood pressure, called ambulatory blood pressure monitoring (ABPM), may be ordered by your doctor to provide a more accurate picture of your blood pressure over time. ABPM may be done if a manual or an electronic method of measurement yields inconsistent results.

ABPM automatically records blood pressure over a period of a few hours to an entire day. The device generally consists of a cuff worn on one arm and a monitor worn around the waist. Your doctor's office will fit you with the monitor and provide instructions on its use.

Why It Is Done

Home blood pressure monitoring provides a measurement of a person's blood pressure at different times and in different environments (such as at home and at work) throughout the day. It may be done to:

• Help establish the diagnosis of high blood pressure.
• Monitor the effects of medication taken to lower blood pressure.
• Help people with high blood pressure to see the effects of medications or lifestyle changes on their blood pressure. Home monitoring can help people feel more involved in and more in control of their own health care.
• Monitor the blood pressure of people who are taking medication (such as monoamine oxidase inhibitors) that can cause episodes of high pressure.
• Help diagnose low blood pressure that may be caused by irregular heart rhythms (arrhythmias), certain medications, or other medical conditions.

Blood pressure normally fluctuates from day to day and even from minute to minute, depending upon activity, posture, temperature, diet, drugs, and a person's emotional and physical state.

Home blood pressure monitoring is most effective when the person also records his or her daily activities (such as the time when medication is taken or a stressful event occurs) in a diary. This can help explain an unusual blood pressure reading and help a doctor accurately adjust medication dosages.

Some people experience a significant rise in blood pressure only when they are in a doctor's office. This is called office or white-coat hypertension and is probably caused by anxiety about the doctor visit. By monitoring blood pressure at home, these people can often find out if their blood pressure readings are generally lower when they are not in the doctor's office. In some cases, ambulatory blood pressure monitoring (ABPM) may also be done to help diagnose white-coat hypertension.

How to Prepare

Do not eat, use tobacco products, use medications known to raise blood pressure (such as certain nasal decongestant sprays), or exercise (for at least 30 minutes) before taking your blood pressure.

Avoid taking your blood pressure if you are nervous or upset. Rest at least 15 minutes before taking a reading.

How It Is Done

Specific instructions

When you first get a blood pressure device, check its accuracy by comparing readings from it with readings obtained by a doctor or nurse taken on a professional mercury column or aneroid device. Ask your doctor or nurse to observe your technique to make sure that you are using it correctly. It is a good idea to have your device checked every year.

The size and position of the blood pressure cuff can greatly affect the accuracy of blood pressure readings. If the cuff is too small or too large, the measurements will be inaccurate. As a general rule, the inflatable part of the cuff needs to be at least as long as the widest measurement around your upper arm. Hospital and medical supply stores generally carry a variety of cuff sizes.

Record your blood pressure while you are seated in a comfortable, relaxed position. Try not to move or talk while you are measuring your blood pressure. Be aware that the blood pressure readings may be 10 to 20 mm Hg different between your right arm and your left arm. For this reason, you may want to use the same arm for every reading. Blood pressure readings also vary throughout the day. They are usually highest in the morning, decrease throughout the day, and are lowest in the evening.

The instructions for using blood pressure monitors vary, depending upon the specific blood pressure device you choose. Here are the basic principles.

Manual blood pressure monitors: Sit with your arm slightly bent and resting comfortably on a table so that your upper arm is on the same level as your heart. Expose your upper arm (roll up your sleeve, but not so tight as to constrict blood flow). If you are unable to roll up your sleeve, remove your arm from the sleeve or take off your shirt. Wrap the blood pressure cuff snugly around your upper arm so that the lower edge of the cuff is about 1 in. (2.54 cm) above the bend of your elbow.

A large artery (called the brachial artery) is located slightly above the inside of your elbow. You can check its location by feeling for a pulse in the artery with the fingers of your other hand. If you are using a stethoscope, place the ear pieces in your ears and the bell of the stethoscope over the artery, just below the cuff. The stethoscope should not rub on the cuff or your clothing, since this may cause noises that can make your pulse hard to hear. If you are using a cuff that has the stethoscope bell built in, be sure the part of the cuff with the stethoscope is positioned just over the artery. The accuracy of a blood pressure recording depends on the correct positioning of the stethoscope over the artery. You may want to have another person who can use a stethoscope properly to help you take your blood pressure.

Close the valve on the rubber inflating bulb. Squeeze the bulb rapidly with your opposite hand to inflate the cuff until the dial or column of mercury reads about 30 mm Hg higher than your usual systolic pressure. (If you don't know your usual pressure, inflate the cuff to 210 mm Hg.) The pressure in the cuff will temporarily stop all blood flow within the artery.

Now open the pressure valve just slightly by twisting or pressing the valve on the bulb. The pressure should fall gradually at about 2 to 3 mm Hg per second. Some blood pressure devices have a valve that automatically controls the fall at this rate. As you watch the pressure slowly fall, note the level on the dial or mercury tube at which you first start to hear a pulsing or tapping sound through the stethoscope. The sound is caused by the blood starting to move through the closed artery. This is your systolic blood pressure.

Continue letting the air out slowly. The sounds will become muffled and will finally disappear. Note the pressure when the sounds completely disappear. Record this as your diastolic blood pressure. Finally, let out all the remaining air to relieve the pressure on your arm.

Electronic blood pressure monitors: For electronic models, press the on/off button on the electronic monitor and wait until the ready-to-measure "heart" symbol appears next to zero in the display window. Then press the start button. The cuff will automatically inflate to approximately 180 mm Hg (unless the monitor determines that you require a higher value). It then begins to deflate automatically, and the numbers on the screen will begin to drop. When the measurement is complete, the heart symbol stops flashing and your blood pressure and pulse readings are displayed alternately.

All blood pressure monitors: Repeat the same procedure 2 more times, for a total of 3 readings. Wait 5 to 10 minutes between recordings while the blood flows unimpeded in your arm. Record your systolic and diastolic pressures, the date and time, which arm you used (left or right), and your position (sitting, standing, lying). Once you become accustomed to taking your own blood pressure, you will probably need to take it only once or twice.

Inspect your blood pressure cuff frequently to see that the rubber tubing, bulb, valves, and cuff are in good condition. Even a small hole or crack in the tubing can lead to inaccurate results.

How It Feels

You may feel some discomfort when the blood pressure cuff inflates, squeezing your arm.

Risks

There are no risks or complications from this test.

Results

The Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNCVI) provides recommended blood pressure measurements for adults over age 18.

JNCVI recommends regular blood pressure checks by a health professional based on a person's initial blood pressure reading.

A diagnosis of hypertension is based on the average of 2 or more blood pressure readings taken at each of 2 or more visits after an initial screening. The 1997 JNCVI defines three stages of high blood pressure (hypertension).

The blood pressure goal for people with diabetes is a systolic (upper) value of 130 mm Hg or lower and a diastolic (lower) value of 85 mm Hg or lower.

Generally, as long as you don't have symptoms such as lightheadedness or faintness, the lower your blood pressure the better. If your blood pressure is usually below 90/60 mm Hg and you feel well, don't worry. However, if your blood pressure normally runs higher than your most recent blood pressure reading, consult a health professional.

What Affects the Test

• If you have poor hearing or eyesight or limited manual dexterity, you may not be able to use a manual blood pressure monitor well enough to get accurate results. For people with these limitations, an electronic arm- or wrist-cuff model is a better choice.
• The size and position of the blood pressure cuff can greatly affect the accuracy of blood pressure readings. If the cuff is too small, the measurements can be falsely elevated. A cuff that is too large can cause a falsely low measurement.

What to Think About

• To check the accuracy of your blood pressure device, you may wish to take your monitor to your health appointment on a yearly basis to compare blood pressure reading from your monitor with those obtained by your health professional.
• Your blood pressure may vary considerably from day to day and from moment to moment. Blood pressure tends to be higher in the morning and lower at night. Stress, smoking, eating, exercise, cold, pain, noise, medications, and even talking can affect it. A single elevated reading does not mean you have high blood pressure (hypertension). Conversely, a single normal reading does not necessarily mean you do not have high blood pressure. The average of several repeated measurements throughout the day is more accurate than a single reading.
• Do not adjust your blood pressure medications based on home blood pressure readings without first discussing any change with your doctor.
• Early detection and treatment with a combination of medication and lifestyle changes (weight loss, diet, exercise, stress reduction) may reduce the health risks associated with high blood pressure. If you are under treatment for high blood pressure, monitoring your blood pressure once a month or once a week is sufficient, though more frequent monitoring may be useful if your blood pressure is not well controlled or if your medications are being changed. Talk to your doctor about how often you should monitor your blood pressure.
• A large difference (greater than 20 mm Hg) between the blood pressure measurements of the right and left arms may indicate a problem. A condition called coarctation of the aorta can cause blood pressure to be much higher in the right arm than in the left arm.
• Some companies offer to collect home blood pressure readings and prepare reports that can be distributed to the person and his or her doctors. People who use this service take their blood pressure readings with an automatic blood pressure monitoring device that can relay those readings over a phone line to a service center. People at the service center process the data, then prepare and distribute reports to each person and his or her doctors.
• Finger blood pressure monitors are the least accurate type of home blood pressure monitor available and are not recommended.