Home Blood Pressure Test
A home blood pressure test allows you to keep track of your blood pressure at home. Blood pressure is a measure of the force of blood inside an artery. 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. Blood pressure is recorded as two measurements.
These two pressures are expressed in millimeters of mercury (mm Hg) because the original devices that measured blood pressure used a column of mercury. Blood pressure measurements are recorded as systolic/diastolic (say "systolic over 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 (say "120 over 80").
Types of blood pressure monitors
The two general types of blood pressure monitors commonly available are manual and automatic.
Manual blood pressure monitors
Manual models are similar to those that your doctor might use to take your blood pressure. Called a sphygmomanometer, these devices usually include an arm cuff, a squeeze bulb to inflate the cuff, a stethoscope or microphone, and a gauge to measure the blood pressure.
Blood pressure is displayed 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.
Automatic (also called electronic or digital) blood pressure monitors
Electronic battery-operated monitors use a microphone to detect blood pulsing in the artery. You do not need 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.
The type of blood pressure monitor typically found in supermarkets, pharmacies, and shopping malls is an electronic device.
Ambulatory blood pressure monitoring (ABPM)
Ambulatory blood pressure monitoring (ABPM) is another method that may be ordered by your doctor if other methods do not give consistent results. It is often used if there is a big difference between the blood pressure readings you get at home and your readings in your doctor's office.
An ambulatory blood pressure monitor is a small device that is worn throughout the day, usually for 24 or 48 hours. The device takes your blood pressure automatically. The device periodically inflates and takes blood pressure measurements, which are recorded for later printout and analysis. The devices are usually loaned by a clinic or hospital.
If you are required to use an ambulatory blood pressure monitor, keep in mind that it is important for a health professional to properly size the cuff, which fits around your arm. Fitting does not take long.
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Why It Is Done
Home blood pressure monitoring measures your blood pressure at different times and in different places (such as at home and at work) during the day. It may be done to:
Ambulatory blood pressure monitoring (ABPM) is often used if there is a big difference between the blood pressure readings you get at home and your readings in your doctor's office.
How To Prepare
Before you take your blood pressure:
Remember that blood pressure readings vary throughout the day. They usually are highest in the morning after you wake up and move around. They decrease throughout the day and are lowest in the evening.
Ambulatory blood pressure monitoring
If you have an ambulatory blood pressure monitor, you do not need to do anything to prepare. The monitor will automatically take your blood pressure while you do your normal daily activities.
How It Is Done
When you buy a blood pressure monitor, be sure to buy the correct size. The size of the blood pressure cuff and where you place the cuff on your arm can change your blood pressure readings. If the cuff is too small or too large, the measurements will not be accurate. Hospital and medical supply stores generally carry many cuff sizes and can help make sure that your cuff fits you. See a picture of a cuff with the proper fit.
Take your new monitor to your doctor's office to make sure it is working right. Have your health professional take your blood pressure and then compare that result with your own device. Ask your health professional to watch you use your monitor to make sure that you are using it correctly. It is a good idea to have your monitor checked every year.
Your blood pressure in your right arm may be higher or lower than the blood pressure in your left arm. For this reason, try to use the same arm for every reading. Blood pressure readings also rise and fall at different times during the day. They are usually highest in the morning and lowest in the evening. Ask your doctor if you should take your blood pressure at the same time of day each time you take it, or if you should take your blood pressure at different times of the day.
The instructions for using blood pressure monitors vary depending upon the type of blood pressure monitor you choose. Here are some general guidelines:
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 by rolling up your sleeve but not so tightly as to constrict blood flow. If you are not able 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. (2.5 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 earpieces 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 with a built-in stethoscope bell, 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 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 or until the pulse at your wrist disappears.) The pressure in the cuff will stop all blood flow within the artery temporarily.
Now open the pressure valve just slightly by twisting or pressing the valve on the bulb. The pressure should fall slowly at about 2 to 3 mm Hg per second. Some blood pressure devices have a valve that automatically controls this rate. As you watch the pressure slowly fall, note the level on the dial 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. If you have trouble hearing the start of your pulse through the stethoscope, you can check your systolic blood pressure by noting the level on the dial when you are able to feel the pulse at your wrist once again.
Continue letting the air out slowly. The sounds will become muffled and will finally disappear. Note the pressure when the sounds completely disappear. This is your diastolic blood pressure. Finally, let out all the remaining air to relieve the pressure on your arm.
Be sure to write your numbers in your log book, along with the date and time.
Electronic 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 by rolling up your sleeve but not so tightly as to constrict blood flow. If you are not able 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. (2.5 cm) above the bend of your elbow.
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 inflate automatically 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
At first it is a good idea to take your blood pressure 3 times in a row, 5 or 10 minutes apart. As you get more comfortable taking your own blood pressure, you will only need to measure it once or twice each time.
Check 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.
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How It Feels
You may feel some discomfort when the blood pressure cuff inflates, squeezing your arm.
There are no risks or complications from this test.
Blood pressure readings of less than 90/60 mm Hg are normal as long as you feel well. In general, the lower your blood pressure, the better. But if you have low blood pressure and feel lightheaded, faint, or like you may vomit, talk to your doctor.
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:
Blood pressure normally goes up and down from day to day and even from minute to minute, depending upon how active you are, whether you are standing up or sitting down, and what medicines you are taking. Other things that can change blood pressure include being too hot or too cold, whether you have recently eaten, and whether you are relaxed or feeling stressed.
Home blood pressure monitoring works best when you also record your daily activities, such as the time you take medicine if you feel upset or stressed, in a diary. This can help explain changes in your blood pressure readings and help your doctor adjust your medicines.
Your blood pressure may only be high when you go to your doctor's office. This is called white-coat (or office) hypertension and may be caused by stress about seeing your doctor. When you regularly check your blood pressure at home, you may find that your blood pressure is lower when you are not at the doctor's office.
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