Monitoring Blood Pressure at Home
If you have been diagnosed with high blood pressure, known medically as hypertension, your doctor may recommend that you use a home monitor to check your blood pressure between visits.
Reviewed By Michael Smith
High blood pressure has been called the "silent killer." The name may seem grandiose, but it's unfortunately accurate: High blood pressure has no symptoms and it can lead to life-threatening illnesses, strokes, and heart attacks. While 50 million people in the U.S. are estimated to have high blood pressure, as many as a third of them may not know it.
If you have been diagnosed with high blood pressure, known medically as hypertension, your doctor may recommend that you use a home monitor to check your blood pressure between visits. Despite what you might think, devices that you can buy in the drugstore or at the mall can be reliable, accurate, and affordable. But there are a lot of monitors out there, and it's crucial to get a good one.
What Kind Should I Use?
Of the different types available, Sheldon Sheps, MD, emeritus professor at the Mayo Clinic in Minnesota, says that you should get only an electronic one with a digital display. The other kinds -- such as aneroid or mercury devices -- require training with a stethoscope to get accurate readings.
"The automated electronic equipment is very simple to use and very reliable," says Michael Weber, MD, Professor of Medicine at the SUNY Health Science Center in Brooklyn. "They're so accurate that many clinical trials are now actually using the same blood pressure machines that you can buy from the drugstore."
However, of these electronic devices, Weber and Sheps urge you to get a device that measures your blood pressure with a cuff around the arm. Don't buy one that works on the wrist, and definitely avoid finger blood pressure monitors, since they are especially unreliable.
A good device costs between $40-$60, although models with additional features are pricier. Some offer a self-inflated cuff, which saves you the trouble of pumping it up yourself. Other devices have a memory of previous readings, and some even print a record each time you use it. Sheps observes that a company's line of devices will often all use the same microchip, so a no-frills model is often as accurate as a more expensive one made by the same company.
Of the extra features, Weber and Sheps suggest getting the self-inflating cuff. For one, pumping it up may be difficult for people with arthritis. "And pumping is a muscular activity," says Sheps, "so it can actually affect your blood pressure reading."
One of the most important things to consider when buying a device is to make sure that the cuff fits your arm. If it's too small or too big, you won't get correct readings. As a rule of thumb, make sure that the cuff fits easily around your arm with fabric to spare. If the cuff that comes with your monitor doesn't fit, you may be able to get a larger one from a drugstore or directly from the manufacturer.
And don't forget to shop around. "The same device may cost twice as much at a medical supply store as it does at a chain store," says Sheps.
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Stay Away From In-Store Machines
What about those freestanding blood pressure machines that supermarkets and pharmacies have set up in lobbies and waiting areas? Both Weber and Sheps say you can't rely on them.
"I am not enraptured with those machines," says Weber. "They get a lot of abuse, and it's hard to tell if they're being maintained and calibrated."
In addition, the cuff size may not fit correctly or it may be uncomfortable, and people with arthritis may have difficulty getting their arm into the machine.
Going to the Doctor
One benefit to self-monitoring is that it allows you to see if your high blood pressure is really just "white-coat hypertension." For many people, just the sight of a stethoscope or the smell of a doctor's office waiting room can send the blood pressure skyrocketing, even if it's normal most of the time. Unless you take readings outside of a medical setting, there's no way to tell if you really do have high blood pressure or not.
Sheps observes that self-monitoring can also help with the reverse: People who have normal blood pressure in the doctor's office but high blood pressure elsewhere, such as on the job.
As useful as they are, your own readings from a blood pressure monitor are no substitute for regular visits to the doctor. Instead, they are just a supplement.
It's important that you periodically check your device against the readings your doctor gets when he or she takes your blood pressure. In fact, Sheps and Weber recommend that you bring your monitor to your doctor after you buy it to make sure that it's accurate, that you have the right cuff size, and that you are using it correctly.
Also, some people may not be able to get accurate blood pressure readings because of certain illnesses or birth defects.
In certain cases, your doctor may recommend something called ambulatory blood pressure readings. A series of blood pressure readings are done outside the doctor's office with a device that automatically checks your pressure a number of times over several hours or days. Typically, you would wear the device for a day or longer and return it to the doctor's office, where he or she could check the readings.
One of the greatest benefits of monitoring your blood pressure yourself is that you will have a much better understanding of your condition. By taking your blood pressure regularly, you can easily tell if your medications are working. You might be inspired to exercise more if you can see the concrete effect it has on lowering your blood pressure.
"We highly recommend self-monitoring of blood pressure," says Sheps. "It helps to have the patient partner with the physician."
Weber agrees. "People who check their own blood pressure tend to be more conscious of the importance of taking their medication on a regular basis," says Weber, "and they tend to be the sort of people who notice the foods or behaviors that raise their blood pressure" and adjust their lifestyle to avoid them.
"It's my belief that patients who get involved in managing their own high blood pressure have much better results and much better outcomes," says Weber.
How To Take Your Blood Pressure At Home
Blood pressure is the force of the blood as it moves through your arteries. It is usually shown as two numbers, such as 120/80 mmHg. The top number is the systolic pressure, which is the pressure recorded when blood is being forced through the arteries by the heart. The bottom number is the diastolic pressure, which is the reading taken between heartbeats.
For a diagnosis of hypertension, your blood pressure would probably be 140/90 mmHg or higher. People with isolated systolic hypertension, which is more common in the elderly, have a normal bottom number but a top number of at least 160.
Taking your blood pressure with an automated monitor is easy, but getting an accurate reading does have a few requirements.
- Avoid tobacco, caffeine, and food for about 30 to 60 minutes before taking a reading.
- Sit quietly for at least five minutes before taking a reading. If you are excited, angry, or upset, your reading may not be typical.
- Sit in a chair with your back supported and your feet flat on the floor.
- Place your arm on a table so that it is level with your heart.
- During the reading, sit still.
- Once the reading is finished, wait a few minutes and take it again. Then average the two readings.
- Keep a log of your blood pressure, also noting the time of day and any other factors that might have influenced the reading. If your monitor automatically keeps a record, you can rely on that, but remember that it won't be much good if more than one person in your house is using the same device.
- Check with your doctor about how often you should take your blood pressure. If your blood pressure is under control, Sheps says that one or two times a month may be fine. If you're trying new medications, your blood pressure is unusually high, or you have other illnesses like diabetes, your doctor may ask that you take it more often.
- Sheps says that most people's readings are lower at home than at the office. Because of this, the target range should be a little lower. "For instance," says Sheps, "if your physician and you have decided that your blood pressure should be less than 140/90 mmHg in the office, then it should not be higher than 135/85 mmHg at home."
- Take care of your monitor. If your drop or damage it, make sure to have it tested again.
Published Jan. 17, 2003.
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SOURCES: Sheldon Sheps, MD, emeritus professor of medicine, division of hypertension, Mayo Clinic, Rochester, Minnesota * Michael Webber, MD, associate dean and professor of medicine at the State University of New York Health Science Center at Brooklyn; editorial board of American Journal of Hypertension * American Society of Hypertension web site * American Heart Foundation web site <bullet> Agency for Healthcare Research and Quality, U.S. Department of Health and Human Services web site * WebMD Medical News: "People with Hypertension Most Often Wrong When Testing Their Own Blood Pressure."
©1996-2005 WebMD Inc. All rights reserved.
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