Figure 2

O ₂ Hb and CO ₂ Hb concentration changes during BH of a healthy subject. Time course of the O₂Hb (blue line) and CO₂Hb (red line) concentration signals during BH. The graph is relative to a healthy subject. Values are scaled in order to set the initial (i.e., at the BH onset) concentration equal to zero. 1) Initial phase with concentration similar to the baseline values; 2) onset of vasoreactivity with strong O₂Hb increase; 3) end of the vasoreactivity and plateau region for the O₂Hb concentration, with increasing CO₂Hb concentration.