Blood Pressure Monitoring during Daily Life
Two general strategies have been employed to obtain measures of blood pressure during daily life: home monitoring and ambulatory monitoring. Home monitoring typically involves training the patient (or a family member of the patient) to operate an occluding cuff properly to obtain auscultatory measures of blood pressure on a daily basis.
In contrast, ambulatory monitoring typically employs an automated device that is programmed to measure blood pressure at periodic intervals over the course of a specified time period, typically 24 or 48 hours.
Let’s examine the costs and benefits associated with each of these approaches.
Home Blood Pressure Monitoring
Home monitoring is one fairly inexpensive strategy for obtaining auscultatory measures of blood pressure out of the clinic. Obviously, this approach relies on having a patient who possesses the manual dexterity and sensory capabilities to acquire the skill of auscultation, adhere to the physician’s instructions regarding frequency of recording, and report blood pressures honestly and accurately. For persons who are uncertain about their ability to acquire this skill, inexpensive devices that automatically inflate and deflate the occluding cuff and detect Korotkoff sounds may be used, although the accuracy of many of these instruments is questionable (Evans et al., 1989; O’Brien et al., 1990).
Validation of Home Blood Pressure Monitors
In an effort to evaluate the accuracy of automated instruments for the purposes of home blood pressure monitoring, the Consensus Conference on Self-Blood Pressure Measurement (White et al., 1999) recommended that these automated instruments be validated according to standards established by both the Association for the Advancement of Medical Instrumentation (1993) and the British Hypertension Society (O’Brien et al., 1993). In brief, these standards allow for discrepancies between blood pressures measured by an automated device and a valid reference device to average no more than +5mm Hg and possess variabilities of no more than 8mm Hg.
Additionally, these standards emphasize training persons to operate the instrument properly and assuring the regular calibration of the device. Although the application of these standards to more recent versions of automated blood pressure recording instruments has held the industry accountable for manufacturing devices that measure accurate blood pressures (Yarows and Amerena, 1999; Yarows and Brook, 2000), some legitimate concern continues to be expressed that these devices still do not measure blood pressure accurately for many individuals (Gerin et al., 2002).
For example, in one recent device validation study, Ploin et al. (2002) reported that the test device met the designated accuracy criteria, even though only slightly over half of the blood pressure determinations obtained from it met the + 5mm Hg criteria and approximately 10 percent of the SBP determinations exceeded a +15mm Hg discrepancy between methods. It would appear that at least for some hypertensive patients, automated devices developed for home use lack the degree of accuracy we have come to expect in medical devices.
In lieu of purchasing an automated device for home blood pressure monitoring, some individuals have turned to using public automated machines, now found in almost all drugstores. In general, this approach has been discouraged (Conway, 1986), because these devices are often not properly calibrated and maintained. Furthermore, taking one’s blood pressure in a public place presents the individual with a whole new set of stimuli that are typically contraindicated in standardized instructions for obtaining accurate measures of blood pressure either in the clinic or at home.