Time course of the values of arterial oxygen saturation (SpO
) and brain tissue O
partial pressure (PtO
) recorded in control rats. No changes were found in SpO2 and PtO2 values over the 60 min of the experiment. Results are shown as mean ± SE (n = 8). The time dependence of arterial SpO2 and brain tissue PtO2 was assessed with a Friedman repeated measures ANOVA by comparing sample points at the first apnea and during the apneas at minute 10 and every 10 min up to 1 h with respect to baseline.