Hb and CO
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.