It’s important to have an accurate measurement of your blood pressure. Here is what to know about the devices used for measuring blood pressure and how to prepare yourself.
At your physician’s office, blood pressure is measured with a device called a sphygmomanometer, which typically consists of an inflating bulb, an inflatable or compression cuff, and a gauge.
The doctor or nurse wraps the cuff around your upper arm and squeezes the bulb to inflate the cuff. Then the air in the cuff is slowly released, which gradually deflates the cuff and lowers the pressure constricting your arm. While this occurs, the doctor or nurse listens for the pulse in your arm with a stethoscope. Systolic pressure is the point at which the pulse is heard for the first time; diastolic pressure is the point at which the sounds of the pulse disappear.
Taking the following steps helps ensure an accurate reading:
• You should not smoke, exercise, or consume caffeine in the 30 minutes before having your blood pressure measured.
• You should be seated and at rest for at least five minutes before the measurement is taken. Keep your feet flat on the floor, and don’t cross your legs
• The doctor or nurse should place the cuff over your bare arm, not over your shirtsleeve.
• Two or more blood pressure readings should be taken at least one minute apart and then averaged.
A formal diagnosis of hypertension is made when average systolic blood pressure is 140 mm Hg or higher, or average diastolic blood pressure is 90 mm Hg or higher, on at least two separate doctor visits. A proper evaluation also requires a thorough medical history, a physical examination, and laboratory tests to identify lifestyle habits and other factors (such as another health problem or a medication) that may be contributing to hypertension.
Ambulatory blood pressure monitor
Your doctor may ask you to wear a device called an ambulatory blood pressure monitor for a day or two. This device automatically measures and records your blood pressure during normal day-to-day activities. These measurements can help your physician diagnose white-coat hypertension. If you already have high blood pressure, ambulatory monitoring can help your doctor understand if changes need to be made to your medications to better control your blood pressure.
If your doctor recommends ambulatory monitoring, you will wear an inflatable cuff around your arm under your clothing. The cuff will be connected to a blood pressure monitor, which is placed in a holster-like carrier at the waist. At predetermined times—typically every 15 to 30 minutes during the day and every 30 to 60 minutes through the night—the cuff will inflate automatically and take your blood pressure. The readings are automatically stored in the monitor and later transferred to your doctor’s computer, where the data can be reviewed and interpreted.
The monitor is lightweight and quiet, and you’ll be able to sleep and carry out your normal activities while wearing it. In rare cases, people experience minor bruising, swelling or a rash, but these side effects are temporary.
Home blood pressure monitors
Experts now recommend that all people with high blood pressure purchase a home monitor to follow their blood pressure readings between office visits. That’s because, compared with office measurements, home monitors provide a more complete picture of your average blood pressure level, predict your risk of heart attacks and strokes more accurately, and provide instant feedback as to whether or not your treatment regimen is working. Still, a home blood pressure monitor is not a substitute for regular visits to your doctor’s office.
Two types of home monitors are available: manual and digital. Manual monitors consist of a cuff, stethoscope, and dial gauge; digital monitors, a cuff and a digital screen. Both manual and digital monitors can provide accurate readings, but digital monitors are recommended because they are easier to use and have a memory feature for tracking your blood pressure readings.
The simplest to use is an automatic digital device: All you need to do is wrap the cuff around your upper arm and press a button to inflate the cuff, and the monitor takes your blood pressure and displays the result. Wrist and finger monitors should be avoided, however, as they are less accurate.
To get the most accurate results, carefully read the manufacturer’s instructions, ask your doctor how to use the device, and have the device’s accuracy checked annually at your doctor’s office. Using a cuff that is the correct size is essential as well, so ask your doctor to check the fit. A cuff that is too small or too large can lead to inaccurate readings. Your doctor will also advise you on the appropriate frequency for taking home measurements.
The American Heart Association offers an online instructional video for home blood pressure monitoring.
Public blood pressure monitors
You may be tempted to measure your blood pressure with the devices at some pharmacies. However, like home monitors, these devices are not a substitute for blood pressure measurements at your doctor’s office. In addition, they may not be calibrated regularly and thus can give inaccurate readings.