Which one of the following is the fastest acting inhalational agent?

Blood-gas paition coefficient, also known as Ostwald coefficient for blood-gas, is a term used in pharmacology to describe the solubility of inhaled general anesthetics in blood. The coefficient is defined as the ratio of the concentration in blood to the concentration in gas that is in contact with that blood when the paial pressure in both compaments is equal. It is inversely propoional to the induction rate. It determines the onset of induction and recovery. anesthetic blood gas solubility Nitrous oxide 0.47 Halothane 2.4 Isoflurane 1.4 Sevoflurane 0.65 Desflurane 0.45 Methoxyflurane 12 Enflurane 1.9 Newer anesthetics (such as desflurane) typically have smaller blood-gas paition coefficients than older ones (such as ether); these are preferred because they lead to faster onset of anesthesia and faster emergence from anesthesia once application of the anesthetic is stopped.