Potency of inhalational anesthetic agent is measured by-

Ans. is 'a' i.e., Minimum alveolar concentration o Minimum alveolar concentration (MAC) & Oil: gas partition cofficient (lipid solubility) - Measure of Potencyo Blood : gas partition coefficient - measure blood solubility and speed of induction & recovery.Minimal alveolar concentration (MAC)o Most important measure of potency is minimal alveolar concentration (MAC). MAC is the lowest concentration of the anaesthetic in pulmonary alveoli needed to produce immobility in response to a painful stimulus (surgical incision) in 50% individuals. Higher the MAC, less potent the anaesthetic agent.o Methoxyflurane has minimum MAC (0.16%). The most potent inhalational agent.o N2O has maximum MAC (105). The least potent inhalational agent.o Order of potency in decreasing order (MAC in increasing order):Methoxyflurane (MAC = 0.16 %) > Trilene (MAC = 0.2%) > Halothane (MAC = 0.74%) > Chloroform (MAC = 0.8 %)> Isoflurane (MAC = 1.15 %) > Enflurane (MAC = 1.68%) > Ether (MAC = 1.92 %) > Sevoflurane (MAC = 2.0 %) > Desflurane (MAC = 6.0%) > Cyclopropane (MAC = 9.2%) > N2O (MAC 104%).