Second gas effect is seen with -

Ans. is 'b' i.e., Nitrous oxide Second gas effecto If another inhalation agent is (eg Halothane) is being given at the same time with N2O2 it also will be delivered to lung from the cylinder (due to negative intraalveolar pressure).Also Remembero Concentration effect and secondary gas effect - during inductiono Diffusion hypoxia - during recovering.o All these occur with N2O only (Xenon also causes these effects).