Central venous oxygen saturation (A) and liver tissue oxygen partial pressure (B) throughout the experiment. BL = baseline; GIOA = gradually increased oxygen administration; PR = postresuscitation; PS = postshock. §P < 0.05 values in the hyperoxic group differ from those in the normoxic group; †P < 0.05 values in the hyperoxic group differ from those in the hypoxemic group; ¶P < 0.05 values in the GIOA group differ from those in the normoxic group; ȻP < 0.05 values in the GIOA group differ from those in the hypoxemic group. All data are expressed as mean ± SD.