Fig. 5. The concentration-effect relation of propofol for respiratory depression depends on the rate of application (simulation results). (Top ) Effect compartment concentration time course of propofol after a 100-mg bolus (solid line ) and an infusion yielding a steady state concentration equal to the peak concentration after the bolus (dashed line ). (Bottom ) Corresponding time courses of Paco2and fractional alveolar ventilation. Solid line = values corresponding to bolus application; dashed line = values corresponding to infusion. The direction of change defines Paco2and ventilation plots (ventilation decreases, Paco2increases). Because of the effect of carbon dioxide in the non-steady state, equal concentrations do not correspond to equal effect.