Dear Doctor Column, June 14, 2004

Keeping Track With a Home Blood Pressure Monitor

Question:

My doctor suggested I buy a blood pressure monitor to use at home to keep a daily log of my readings, since I am borderline hypertensive. What do you recommend? I think the digital kind would be easiest for me to use, since I live alone.

Answer:

As your doctor explained, a home blood pressure (BP) monitor can help you keep track of your BP between checkups, allowing you to quickly spot trends or pick up any sudden changes in your readings. Since borderline hypertension is a strong precursor of future hypertension, study researchers conclude that simple and inexpensive home BP monitoring is helpful in predicting which borderline hypertensive patients will go on to develop persistent high BP.

Although home BP monitoring doesn't serve as a substitute for regular evaluation by your doctor, a University of Michigan study found BP readings obtained when patients were trained to measure their own readings at home better reflected a persons true BP, compared with readings taken during visits to the doctor's office. Another study published in the March 17, 2004, Journal of the American Medical Association showed BP readings taken at home also may predict future risk of heart-related problems more accurately than those taken at a doctor's office.

Most BP monitors have an inflatable cuff that wraps around the upper arm. When inflated, the cuff acts as a tourniquet, cutting off blood flow. While slowly turning a valve that releases air trapped in the cuff, you listen over the artery in your elbow with a stethoscope for the characteristic "lub-dub" sounds that signal return of blood flow through the artery.

When you hear the first sound, you look at the BP gauge and make a note of the pressure. That number represents the systolic pressure generated by the flow of blood through the artery as the heart pumps. When the sound totally disappears, that's the diastolic pressure — the pressure generated by blood flow when the heart is resting between beats.

BP is expressed as how many millimeters the pressure of blood flowing through the artery can raise a column of mercury. It is reported as systolic over diastolic pressure, for example, 120/80 millimeters of mercury (120 over 80); systolic=120, diastolic=80.

Variety of Choices

There are lots of makes and models of BP monitors from which to choose, with a variety of features, and prices begin as low as $20. Three common types of home BP monitors are aneroid, mercury, and electronic/digital readout. A stethoscope is needed with the mercury and aneroid monitors, but electronic/digital readout devices have the stethoscope built into the cuff.

A mercury monitor is the standard against which all other BP measurement devices are checked. It gives consistent and accurate readings and is most often used in hospitals and doctors offices.

When choosing a home BP monitor, keep these factors in mind — ease of use, accuracy, portability, reliability, durability, and cost. The biggest advantage of the electronic/digital models is the convenience; you slip on a cuff and press a button. The cuff automatically inflates, "listens" for the lub-dub sounds, and displays your BP.

Finger-pulse electronic monitors and wrist monitors now on the market have not proven to be as accurate as the others. BP readings on stationary automated BP machines like the ones found in supermarkets, drug stores, and airports, can vary considerably between machines, since they must be calibrated often.

New Guidelines

Last year, the National Heart, Lung, and Blood Institute, part of the National Institutes of Health, released new clinical practice guidelines for the prevention, detection, and treatment of high BP, known medically as hypertension.

The new guidelines were published in the May 21, 2003, issue of The Journal of the American Medical Association. The last guidelines were issued in November 1997. Since then, much more has been learned about the risk of high BP and the course of the disease. For instance, Americans' lifetime risk of developing hypertension is much greater than once thought: Individuals with no prior history of hypertension still have a 90% risk of developing the condition after age 55.

New BP Classifications

The bottom line is that Americans must change how they think about BP. It is vital that adults adopt a heart-healthy lifestyle early, even if their BP is normal.

For more information on the new guidelines, visit the American Heart Association Web site.