Figure 5-11 When no ventilation-perfusion abnormalities exist, the alveolar (PA) and arterial (Pa) anesthetic partial pressures rise together (solid lines) toward the inspired partial pressure (PI). When 50% of the cardiac output is shunted through the lungs, the rate of rise of the end-tidal partial pressure (dashed lines) is accelerated, and the rate of rise of the arterial partial pressure (dotted or dashed lines) is retarded. The greatest retardation occurs with the least soluble anesthetic, cyclopropane. FA/FI is the alveolar concentration of anesthetic/concentration of inspired anesthetic. (Adapted from Eger EI II, Severinghaus JW: Effect of uneven pulmonary distribution of blood and gas on induction with inhalation anesthetics. Anesthesiology 25:620–626, 1964.)