Figure 3. Increased ventilation at wake onset from non-REM sleep at a P_ET,CO2 level matched with steady-state wakefulness.

A, mean ventilation over 10 breaths produced by CO₂ added in established wakefulness compared with the mean ventilation at wake onset from sleep at matched P_ET,CO2 levels. Paired data points are shown for each dog represented by a different symbol. B, difference in mean ventilation between established wakefulness and wake onset at matched P_ET,CO2 levels, i.e. the extra ventilation produced by arousal from sleep per se and not attributed to stimulation by CO₂ according to current model. C and D, the same relationships for peak ventilation elicited in the 10 breaths following application of the tone in established wakefulness and wake onset at matched P_ET,CO2 levels. The means ±s.e.m. are also shown, *P < 0.05.