Figure 3. Time course of the effects of placebo-oxygen, 15% and 30% end-tidal nitrous oxide, and 0.3% and 0.6% end-tidal sevoflurane on the number of symbols correctly drawn on the DSST (top), auditory reaction time (middle), and time estimation (bottom). Each time point is the mean for 12 volunteers. Time 0 refers to baseline measures, times 5 and 15 min refer to intrainhalation testing, and times 40, 65, and 95 min represent postinhalation testing. The vertical dashed line separates the 35-min inhalation period from the 60-min recovery period. Asterisks indicate a significant difference from placebo-oxygen, and daggers next to a 0.6% sevoflurane time point refer to a significant difference from the 30% nitrous oxide condition at the same time, as determined by Tukey post-hoc testing.