A TEST OF REPRODUCIBILITY OF BLOOD-PRESSURE AND HEART-RATE-VARIABILITY USING A CONTROLLED AMBULATORY PROCEDURE

Objective: To determine whether the previously reported poor reproduci bility of blood pressure variability measured by ambulatory blood pres sure monitoring (ABPM) is due to the uncontrolled nature of physical a nd mental activity during the monitoring period. Design: ABPM was perf ormed on two separate days during which subjects performed identical a ctivities, accompanied by the experimenter. Thus, activity and posture were controlled, both within and between subjects. Two measures of va riability were used: SD and the root-mean-square of successive differe nces (RMSSD). Methods: Thirty-seven subjects participated. Each engage d in a series of activities, such as walking outdoors, editing and alp habetizing tasks, and eating lunch, while wearing an A & D 2420 ambula tory blood pressure monitor which took measurements at 5-min intervals . Measures of variability were computed within each session. Results: Contrary to previous reports, reproducibility was moderately high for blood pressure, with significant correlations between SD and between R MSSD for systolic and diastolic blood pressure. Heart rate reproducibi lity was less good. Conclusions: Lack of standardization of activities from one occasion to another is a major reason for the poor reproduci bility of blood pressure variability when measured using ABPM. Even wh en activities are standardized, however, the reproducibility of blood pressure variability is still only moderate and may limit the ability of researchers to detect associations between ABPM variability and oth er measures.