Figure 5-6 An increase in the inspired halothane concentration does not produce a proportional increase in the alveolar concentration because of the progressively greater depression of ventilation that occurs as alveolar halothane is increased. The initial "overshoot" seen with 10% to 20% inspired halothane results from the delay in the transfer of alveolar halothane partial pressure to the brain. FA/FI is the alveolar concentration of anesthetic/concentration of inspired anesthetic. (Adapted from Munson ES, Eger EI II, Bowers DL: Effects of anesthetic-depressed ventilation and cardiac output on anesthetic uptake. Anesthesiology 38:251–259, 1973.)