Time versus frequency domain techniques for assessing baroreflex sensitivity

Background Newer techniques to evaluate baroreflex sensitivity (BRS) are ba sed on the analysis of blood pressure (BP) and heart rate (HR) time series in the time or frequency domain. These novel approaches are steadily gainin g popularity, since they do not require injection of vasoactive substances, nor do they rely on a complex experimental set-up. Aim This review outlines and compares some basic features of the latest met hods to assess spontaneous baroreflex function. Results Modern techniques for the estimation of spontaneous BRS are based o n a variety of signal processing schemes and derive information on the baro reflex function from different perspectives. Thus factors such as respirati on and other non-stationary agents may have different influences on the est imates provided by each of these approaches. Notwithstanding such individua l specificity, however, it has been observed that in several physiological and pathophysiological conditions these techniques often provide comparable information on BRS changes over time, particularly when the estimates are averaged over time windows of a few minutes. Conclusions Due to the general agreement in the pattern of BRS among most m odern methods, it seems reasonable to employ the most validated of these te chniques, for which data obtained in several studies are already available. (C) 2001 Lippincott Williams & Wilkins.