Taking blood pressure: Too important to trust to humans?
ABSTRACTThe measurement of blood pressure in the physician’s office is subject to a number of observer errors and also to the “white-coat effect.” Automatic devices that measure blood pressure without a human observer in the room can eliminate many of these problems. We argue for greater use of these devices in the physician’s office.
KEY POINTS
- The white-coat effect, ie, the tendency of many patients to have higher blood pressure in the presence of medical personnel than in their own environment, can lead to inappropriate diagnosis of hypertension and unnecessary treatment.
- Out-of-office blood pressure correlates better with cardiovascular risk than does the blood pressure in the physician’s office, but ambulatory monitoring is costly and not widely available, and few physicians recommend self-measurement at home.
- Several available devices can take a series of blood pressure measurements at preset intervals while the patient sits alone in the examination room, eliminating the white-coat effect.
- The mean of five automatic readings taken at intervals of 1 or 2 minutes correlates well with the mean value while awake on ambulatory monitoring.
WHAT ROLE FOR AUTOMATED READINGS IN THE OFFICE?
Although automatic devices, by enabling the physician to leave the room, can eliminate the white-coat effect and white-coat hypertension, physicians must continue to take care to avoid the other potential errors of office blood pressure measurement addressed earlier in this review, for example, by positioning the patient correctly and using a cuff that is large enough. These issues can take on more importance as the clinician leaves the patient alone for brief periods during measurements.
In view of its perennial inaccuracies, some experts have suggested that we abandon routine office measurement of blood pressure.35,36 In its place, ambulatory monitoring would be used for diagnosis and for periodic follow-up. In addition, patients would regularly take their pressure at home with approved, single-measurement oscillometric devices. Unfortunately, in our health care system, periodic ambulatory monitoring for hypertension management would impose a significant financial burden on patients at this time.37
Of particular importance is the observation that the mean of five readings with the BpTRU device, obtained at 1- or 2-minute intervals, closely approximates the mean awake blood pressure obtained in the same patient with an ambulatory monitor.32,38 The ability to obtain readings that correlate exceptionally well with mean daytime ambulatory pressure suggests that this device could well reduce the need for ambulatory monitoring, with its associated cost. The ability to negate the white-coat effect with the use of the BpTRU in the office setting also has particular importance, not only for patient office readings, but for the diagnosis and subsequent treatment of hypertension in individual patients.
Most clinical decisions about the treatment of hypertension are still made on the basis of office determinations of blood pressure. Most office practices still rely on the aneroid manometer or, decreasingly, mercury sphygmomanometers. As noted earlier, although auscultatory blood pressure measurement appears to be simple, it is fraught with a host of observer- or patient-induced errors that not only lead to inaccurate diagnoses, but may also result in the mismanagement of hypertension. Even single-measurement oscillometric devices, now used in a minority of clinical practices, are associated with many of the same measurement issues that lead to overestimation of blood pressure.
We believe the time has come for broader use of oscillometric devices in the outpatient setting. While many available oscillometric devices for use in the home could also be used in the physician’s office, they carry the similar disadvantage of providing only a single measurement. The major disadvantage of all single-measurement devices is the continued presence of the clinician during the reading and the associated white-coat effect observed in most patients.
It is highly likely that the next Joint National Committee Report on Hypertension will further emphasize the role of automated blood pressure devices in the outpatient setting.
Acknowledgment: The authors wish to acknowledge the contributions of Deborah McCoy, RN, and Maria Eckhouse, RN.
