Figure 2.

Representative results from the same subject as in Figure 1 for the right middle cerebral artery during sitting (a,d,g,j), standing (b,e,h,k) and repeated squat-stand maneuver at 0.05 Hz (c,f,i,l). (a–c) middle cerebral artery velocity (MCAv), (d–f) original mean arterial blood pressure, (g–i) integrated positive (continuous line) and negative (dashed line) derivatives of mean arterial blood pressure (BP), and (j–l) normalized MCAv responses to a step change in the original MAP (dotted line) and to the integrated positive (continuous line) and negative (dashed line) derivatives of MAP. Signals in (a–i) have been windowed (Hanning) after removing their mean values. The corresponding values of the autoregulation index (ARI) for the MCAv step responses were, 7.7, 3.7, and 2.7 (j); 5.2, 4.6, and 4.0 (k); and 4.0, 3.1, and 1.5 (l) for the original, integrated positive and negative derivatives of MAP, respectively.