At a glance
- Home BP readings are better predictors of cardiovascular risk and target organ damage than are in-office readings.
- A cuff placed on the upper arm is the most reliable method to use for home BP monitoring (HBPM).
- Discourage patients from measuring BP while under stress.
- HBPM devices may be purchased without a prescription.
More than 76 million adults in the United States aged 20 years and older have high BP, according to the NHANES 2005-2008 data.1 This translates to about one in every three Americans having hypertension.1 Approximately 80% know they have the condition, yet only 71% are being treated, with almost half (48%) meeting treatment goals.
By convention, most clinicians base their diagnostic and treatment decisions on in-office BP readings. However, many office readings are misleading, as these numbers do not reflect the “true” average, everyday out-of-office levels. A number of providers have encouraged patients to monitor and record out-of-office BP measurements to obtain additional data that can be used to guide treatment decisions. Ambulatory BP monitoring can achieve the same goal, but can be expensive and cumbersome for the patient to use, and — depending on the billing code — may not be reimbursed by insurance companies.
Prospective studies have demonstrated that multiple readings taken by patients in their homes are better predictors of cardiovascular risk and target organ damage than are BP readings taken in the office. In fact, home BP readings have been shown to be more reproducible than office readings and have better correlations with target organ damage.2 A 2008 call-to-action statement on the use and reimbursement of home BP monitoring (HBPM), jointly written and adopted by the American Heart Association, the American Society of Hypertension, and the Preventive Cardiovascular Nurses Association, advocated for greater use of HBPM by clinicians.2
Indications for HBPM
Many of the patients seen in primary-care and internal-medicine clinics would benefit from HBPM. Thus, HBPM should be a routine component of monitoring those with high BP. More frequent BP monitoring could lead to more accurate and timely diagnosis of patients with prehypertension, suspected hypertension, and/or newly diagnosed hypertension, and could help clinicians evaluate the response to initial treatment strategies. HBPM may also improve adherence to therapy. Another benefit of HBPM is that it provides additional data to evaluate need for treatment in those with suspected white-coat hypertension (higher readings in the office than in the home) or suspected masked hypertension (lower readings in the office than in the home). In addition, HBPM is helpful in managing hypertension in special patient populations—such as the elderly and children—in whom BP variability is common, those whose members are at high risk for cardiovascular complications (individuals with diabetes or kidney disease), and pregnant women.
It is important to note that automatic BP monitoring may be unreliable in persons with atrial fibrillation and other cardiac rhythm disturbances (e.g., frequent ectopic beats). However, this does not mean that HBPM is contraindicated in these patient populations. Rather, the clinician must remember that the BP values may jump around based on where systole occurs during the BP measurement.
Selecting a HBPM device
The most reliable method to use for HBPM is a cuff placed on the upper arm to measure brachial-artery BP. Make sure the circumference of the upper arm is measured carefully to avoid inaccurate readings associated with having the wrong size cuff, a problem encountered by a majority of people unfamiliar with HBPM devices. A cuff that is too large will yield falsely low readings; a cuff that is too small will result in falsely elevated readings.
There are advantages and disadvantages to using wrist monitors, devices preferred by some patients. Wrist monitors may be helpful in obese people who find it difficult to place a BP cuff on the upper arm. However, wrist monitors are less reliable if the cuff is not placed at the level of the heart during monitoring. Finger monitors are not recommended due to the high level of inaccurate readings produced by these devices.
A list of approved and validated monitors is available from the Dabl Educational Trust.3 Monitors may not be 100% accurate for every patient, especially if the person is elderly or has diabetes. Encourage patients to bring home monitors in for validation with in-office readings. This visit also is a good opportunity to educate the patient and/or his or her family members on the proper use of the HBPM device.
To check home monitors for accuracy, have the patient take a sitting position with the arm at heart level. The arm should be completely relaxed and resting either on the desk or cradled in the provider’s arm if readings are taken from the exam table. After allowing the patient to rest for five minutes, five sequential same-arm BP readings should be taken no more than 30 seconds apart. The patient and the health-care provider must avoid any conversation during the measurements to prevent an increase in BP. The entire procedure should take approximately 10 minutes.
The first two readings are taken with the patient’s device. The health-care provider takes the third reading, preferably with a mercury sphygmomanometer. A fourth reading is taken by the patient, followed by the fifth and final reading, which is taken by the health-care provider. In most cases, BP readings will decline over the five measurements, with the final one being as much as 10 mm Hg systolic BP lower than the first. There is no established target for how close the readings from the patient’s cuff should be to those of the provider’s cuff. However, this exercise can provide a general sense of the HBPM device’s accuracy, which can be taken into consideration for future measurements recorded at home. Repeat this procedure annually.