Fig. 3. Methods used to compute cross-correlation BRS. (A and B) Beat to beat SBP and IBI data were fitted with cubic spline functions and resampled at 1-s intervals. (C) In 10-s windows, the correlation and regression slopes between SBP and IBI were computed. Delays of 0- to 5-s increments in IBI were computed, and the delay with the highest positive coefficient of correlation was selected; this optimal delay (Tau) was stored. (D) The slope between SBP and IBI was recorded as an xBRS estimate if the correlations was significant at p=0.01. SBP, systolic blood pressure; IBI, interbeat interval; xBRS, cross-correlation baroreflex sensitivity.