Definition of normalcy in whole-day ambulatory blood pressure monitoring.

In this study we have performed 24-hour ambulatory blood pressure monitorings in age-matched normotensive and hypertensive male subjects. The data have been analyzed in an attempt to define standards for the clinical use of ambulatory blood pressure monitoring in the diagnosis of hypertension. The data were analyzed with respect to possible differences in the averages of the whole-day, daytime and nighttime blood pressures, and differences in the prevalence of abnormal blood pressures between the two groups. A considerable overlap was found between the two groups with respect to the various blood pressure averages. The overlap in blood pressures occurred in fewer patients for diastolic than for systolic blood pressure, and less often when nighttime pressures were considered. Hypertensive men showed on average a greater incidence of abnormal blood pressures than normotensive subjects. However, nine of the normotensive control subjects showed more than 25 percent of abnormal readings of systolic or diastolic blood pressures during a 24-hour recording period. In contrast, fewer than 25 percent of abnormal blood pressure readings were found in 9 of the hypertensive patients. The data reported here may help to better define the use of ambulatory blood pressure monitoring techniques in the diagnosis of hypertension.