Q: A patient whose blood pressures in my office are consistently in the range of 160/95 to 100 mm Hg tells me that her measurements at home, using her son’s oscillometric blood pressure device, are always below 135/85 mm Hg. What is the best method for establishing a diagnosis of office hypertension?
A: You have addressed an issue that is increasingly recognized as a major problem in clinical practice: office hypertension, or “white coat hypertension.” As many as 25% to 35% of patients tend to have higher blood pressures in their provider’s office than they do on self-determination at home, particularly with one of the many oscillometric devices now available for single blood pressure measurements.
WHITE COAT HYPERTENSION VS WHITE COAT EFFECT
The term “white coat hypertension” is used to describe the patient who has persistently elevated clinic or office blood pressure (higher than 140/90 mm Hg) and normal daytime ambulatory blood pressure (lower than 135/85 mm Hg). The term “white coat hypertension” is reserved for those who are not receiving antihypertensive drug therapy and must be distinguished from white coat effect, which is a very common response to an office visit.1
White coat effect can be observed in most hypertensive patients as an elevated office blood pressure with a lower awake ambulatory or home blood pressure, regardless of the presence or absence of hypertension. White coat effect tends to be most apparent with the initial blood pressure measurement, but it can be observed in multiple provider-measured blood pressures during an office visit. In most cases, white coat effect represents patient anxiety about the office visit. It may result in misdiagnosis of hypertension or the severity of hypertension and may lead to overly aggressive therapeutic measures.
Both white coat hypertension and white coat effect can be countered by the use of an automated and programmable oscillometric device that enables the determination of multiple readings in the home.
SHORTCOMINGS OF OFFICE BLOOD PRESSURE MEASUREMENT
Most practitioners still rely on auscultatory aneroid devices or mercury sphygmomanometers to measure blood pressure. Despite the distribution of guidelines for accurate measurement in the office setting, overall accuracy and reproducibility of blood pressure measurement remains poor.2
Patients are rarely advised to refrain from smoking cigarettes or drinking coffee within 30 minutes of a blood pressure measurement, and observers remain guilty of too rapid deflation of the blood pressure cuff during a measurement. Conversation during blood pressure measurement can also contribute to higher readings. In addition, failure to support the arm, with the forearm horizontal and the cuff at heart level, is associated with higher blood pressure and heart rate. Some offices may not have a large blood pressure cuff for overweight patients or a pediatric cuff for children or adults with arms of small circumference. Miscuffing, or the use of an inappropriately sized blood pressure cuff, is a common source of error.
All of these issues affect the accurate measurement of blood pressure in the office and have been stressed for decades in national and international guidelines. Time constraints and a busy practice setting also contribute to these deficiencies. As a result, treatment decisions may be significantly affected by higher blood pressure readings. Most office blood pressures are obtained by the physician or other provider with an auscultatory device, and a major contributor to higher readings is the presence of the provider during the measurement.
NEWER OPTIONS FOR BLOOD PRESSURE MEASUREMENT
In the past decade, numerous studies have reported that 24-hour ambulatory blood pressure monitoring (ABPM) as well as self-measurement of blood pressure in the home with an oscillometric device serve as better predictors of future cardiovascular events than conventional blood pressures obtained in the physician’s office.3,4 Unfortunately, ABPM, despite its proven diagnostic value, is not readily available nor is it cost-effective for long-term management of hypertension.
Self-monitoring of blood pressure at home has now become widely available with the marketing of single-measurement, relatively inexpensive oscillometric blood pressure devices. Blood pressures of lower than 135/85 mm Hg outside the clinician’s office are considered normal with these devices, while blood pressures of lower than 140/90 mm Hg are considered normal in the physician’s office with currently used aneroid devices. Keep in mind that optimal use of home blood pressure devices requires the same simple maneuvers required in the physician’s office.
Most home oscillometric devices are available in different cuff sizes. Blood pressures at home should be obtained at periodic intervals and ideally at different times of the day, such as morning and evening. Measurements should be recorded in a diary and made available to the patient’s physician at the time of office visits. Although the use of home oscillometric blood pressure devices is not widely recommended by practicing physicians, the measurements obtained can be of significant value, not only in the evaluation of possible office hypertension but also in the long-term management of hypertension. However, even in the minority of clinical practices that are now using single-measurement oscillometric devices, they, too, are associated with many of the same measurement problems that lead to overestimation of blood pressure in the office setting.
In the past 5 years, a number of new programmable devices have been developed for office measurement of blood pressure.5,6 These devices utilize oscillometric technology and can be programmed to take multiple readings in the absence of a clinician observer in the room, thus reducing the common white coat response. These devices provide the ability to obtain 3 to 5 readings at intervals of 1, 2, and 3 minutes while the patient rests comfortably in a quiet room. The white coat response can be seen to dissipate within 3 minutes of the observer leaving the examination room. At least one of these devices, the BpTRU, which can take up to 5 blood pressure readings, provides average readings that are comparable to those obtained with 24-hour ABPM.7
The time required for blood pressure measurement with these devices is as little as 5 minutes, which makes them a viable option for busy practices. As the cost of these devices decreases, they will likely become more widely used in the outpatient setting.