An illustration of the experimental range of variation of blood pressure

The nominal uniformity of long-term mean pressure (approximately 100 mmHg at heart level) for all mammalian species belies the broad nature of its variance, which is found at many time scales. Such variations should be a useful index of physiologically normal and pathological processes. However, it is dubious whether a scientifically meaningful determination of central blood pressure at its many process scales can be achieved from a few isolated measurements: to cite a common and highly significant instance, measurement made by a physician on a patient during one or two office visits. The data presented here are far from exhaustive (a few reports in the literature and detailed longitudinal data on 1 subj), but they serve to illustrate a protocol and a sample of the physiological results that might be expected if data were gathered for larger populations. The basic scales of interest lie in the lower-frequency domain, involving periods of fluctuations longer than tens of minutes.