Very low frequency variability in arterial blood pressure and blood volumepulse

Several parameters of the cardiovascular system fluctuate spontaneously owi ng to the activity of the autonomic nervous system. In the study, the simul taneous very low frequency (VLF) fluctuations of the arterial blood pressur e, the tissue blood content and the tissue blood volume pulse are investiga ted. The latter two parameters are derived from the baseline BL and the amp litude AM of the photoplethysmographic (PPG) signal, measured on the finger tips of 20 healthy male subjects: the changes in the PPG parameters AM and BV, defined by BV=const.-BL, are related to the change in the tissue blood volume pulse and the total tissue blood volume, respectively. The VLF fluct uations in BV and AM are directly correlated, those of AM preceding those o f BV by 4-13 heart-beats. The VLF fluctuations in the systolic (SBP) and th e diastolic (DBP) blood pressure are inversely correlated to those of AM an d BV, those of AM preceding those of SEP and lagging behind those of DBP by about one heart-beat. For most subjects, the period P of the PPG pulse, wh ich is equal to the cardiac cycle period, directly correlates with AM and B V and inversely correlates with DBP and SEP. On average, the fluctuations o f P precede those of AM by more than three heart-beats. The measurement of the VLF fluctuations in tissue blood volume, systolic blood volume pulse, d iastolic and systolic blood pressure, and heart period, together with their interrelationship, can provide a better understanding of the autonomic ner vous control of the peripheral circulation and a potential tool for the eva luation of its function.