Modern techniques for the estimation of spontaneous BRS are based on a variety of signal processing schemes and derive information on the baroreflex function from different perspectives. Thus the factors as respiration and other non-stationary agents may have different influences on the estimates provided by each of these approaches. Due to the general agreement in the pattern of BRS among most modern methods, it seems reasonable to employ the most validated of these techniques, for which data obtained in several studies are already available.