Blood pressure fluctuation and amplitude in normal human subjects

Whole-day ambulatory blood pressure monitoring utilizing a portable non-invasive device (Pressurometer III) was performed in 34 normal subjects undertaking their usual activities at work and at home. To evaluate reproducibility, the monitoring procedure was repeated two to six weeks later in each subject. For all subjects together, the averages of the whole-day systolic or diastolic blood pressures on the two study days were not different from each other. For further analysis, each study day was divided into 12 two-hour periods; within each participant, the highest and lowest two-hour averages for systolic and diastolic blood pressures, and the times at which they occurred, were then identified. For the group as a whole, there were no differences between the two study days in the averages of the highest and lowest blood pressure values; moreover, the averages of the times at which they occurred corresponded closely. The blood pressure amplitudes, defined as the differences between the highest and lowest values during the day for each subject, were also similar on the two study days. Thus, as measured by the highest and lowest points of the circadian blood pressure fluctuations, the whole-day time-blood pressure pattern appears to be reproducible from day to day. Of interest is the fact that the amplitudes correlated closely with the standard deviations (regarded as indices of hour-to-hour variability) of the full 24-hour blood pressure averages, indicating that there might be a relationship between short-term blood pressure changes and the pattern of blood pressure for the day as a whole.