Once the home monitor has been checked against in-office BP measurements, a plan for HBPM can be implemented. It is helpful to have the patient’s family member or significant other present during education, and to provide written instructions in case the patient forgets the instructions or someone else helps with the procedure later.
Instruct the patient to refrain from drinking coffee or other caffeinated beverages, smoking, or exercising for at least 30 minutes prior to measuring BP at home. He or she should sit quietly for at least five minutes and place the upper arm in a supported position at the level of the heart. The person’s back should be supported in a chair, with the legs uncrossed and feet placed flat on the floor. If using the arm cuff, the cuff should be positioned at the upper arm (over the brachial artery). Most patients will find it easier to place the cuff on the nondominant arm.
Three readings should be taken each morning followed by three more readings in the evening. BP should be measured before the patient takes any medications (especially for the morning readings). If this is not done, it should be noted in the recordings. Evening readings should be taken before the patient goes to bed. Readings should be taken at least one minute apart, and all should be recorded with the time of each measurement. If the patient has missed his or her medications for any reason, this should be noted on the data sheet. All recordings should be brought to the office visit.
Initially, morning and evening readings should be taken over a one-week period (ideally, over five or six consecutive days). This provides a total of 12 readings to use for clinical decision-making. Thereafter, the provider can choose how many days per week or per month the readings should be taken. All readings from the first two days and the first measurement of each triplicate set of readings thereafter should be discarded.4 Readings from the first two days generally run higher than the patient’s average BP. The average of the remaining BP measurements has been shown to be the best correlation with ambulatory BP monitoring.4
Remind patients that it is normal for BP values to vary, even within the few-minute intervals between readings. Moreover, patients should expect there to be unusually high or low individual readings, but the overall average is what will be used to determine response to treatment. However, there are times that treatment decisions are based on wide BP variation and/or wide pulse pressure (a large difference between systolic and diastolic BP).
Discourage patients from measuring BP when they are under stress.2 Also, some individuals may become overly vigilant about measuring their BP, which causes anxiety and could raise BP. In rare cases, HBPM may be discontinued in those who become obsessed with checking their BP.
Utilizing the data
On average, at least 12 HBPM readings are necessary before any clinical decisions can be made. The more readings that are taken, the more reliable the estimate of the “true” BP is. Additional readings are especially helpful when trying to make an initial diagnosis of hypertension. In the long-term, however, less frequent readings that fit into the patient’s lifestyle may enable him or her to sustain monitoring for years to come.
According to most guidelines, average HBPM readings <135/85 mm Hg (or <130/80 for those at high risk) are considered to be normal.5
Evaluation of special circumstances
HBPM is especially useful when white-coat hypertension, masked hypertension, and/or resistant hypertension is suspected. White-coat hypertension has been shown to be present in as many as 20% of patients diagnosed with hypertension2 and is most common in the elderly. If white-coat hypertension is suspected, use HBPM to validate office measurements. If HBPM measurements confirm the suspicion, evaluate the need to increase therapy with a 24-hour BP test. If the 24-hour average BP is <130/80, continuation of current therapy is recommended; a 24-hour average >135/85 necessitates intensified therapy.6
Masked hypertension—the reverse of white-coat hypertension—afflicts approximately 10% of the population.2 Masked hypertension occurs when office BP measurements are <140/90, despite higher home or ambulatory BP readings. Masked hypertension has been shown to be equivalent to hypertension when considering cardiovascular risk, so it is important for the clinician to obtain HBPM readings in patients who have prehypertension and those who border on being “in control.”
Resistant hypertension is defined as BP that remains above goal despite the concurrent use of three antihypertensive agents from different classes.7 All of the agents should be at optimal doses, and at least one should be a diuretic. HBPM can be useful in evaluating resistant hypertension for those patients with continued elevated BP readings in the office. In some cases, intensification of medication may not be necessary if HBPM readings are lower than in-office readings.
Availability and cost
HBPM devices may be purchased without a prescription at most drugstores or medical-supply stores. Patients should check as to whether HBPM devices are covered in their insurance plan. Consumer Reports recently tested 16 monitors, and the four upper-arm cuff devices judged excellent for accuracy were: (1) the Omron Women’s Advanced Elite 7300W ($100), (2) the Microlife Deluxe Advanced 344534 ($90), (3) the Omron HEM-711AC ($90), and (4) the ReliOn HEM-741CREL ($40). Buying a large adult cuff may add to the overall cost of the device.
HBPM offers a valuable opportunity for patients and providers to work together in diagnosing and managing hypertension. Given proper instruction, the patient can provide accurate and reliable data to aid clinical decision making. HBPM is particularly useful in such special populations as the elderly, those with diabetes or kidney disease, pregnant women, and children.
Dr. Davis is a clinical assistant professor at the University of North Carolina at Chapel Hill in the School of Medicine, Division of Cardiology.
2. Pickering TG, Miller NH, Ogedegbe G, et al. Call to action on use and reimbursement for home blood pressure monitoring: executive summary: a joint scientific statement from the American Heart Association, American Society of Hypertension, and Preventive Cardiovascular Nurses Association. Hypertension. 2008;52:1-9.
4. Verberk WJ, Kroon AA, Kessels AG, et al. The optimal scheme of self blood pressure measurement as determined from ambulatory blood pressure recordings. J Hypertens. 2006;24:1541-1548.
5. Williams B. The year in hypertension. J Am Coll Cardiol. 2009;55:65-73.
7. Calhoun DA, Jones D, Textor S, et al. Resistant hypertension: diagnosis, evaluation, and treatment: a scientific statement from the American Heart Association Professional Education Committee of the Council for High Blood Pressure Research. Circulation. 2008;117:e510-e526.
All electronic documents accessed June 15, 2011.