Diffusion hypoxia seen during ?

Ans. is 'b' i.e., Reversal of anaesthesia Second gas effect and diffusion hvpoxia In initial pa of induction, diffusion gradient from alveoli to blood is high and larger quantity of anaesthetic is entering blood. If the inhaled Concentration of anaesthetic is high (eg N20), Substantial loss of alveolar gas volume will occur and it creates negative intralveolar pressure that leads to removal of more gas from cylinder to alveoli Concentration effect. If another inhalation agent is (eg Halothane) is being given at the same time, it also will be delivered to lung from the cylinder (due to negative intraalveolar pressure) Second gas effect. During recovery reverse occurs - N20 having low blood solubility, rapidly diffuses into alveoli and dilutes the alveolar air --> paial pressure of oxygen in alveoli is reduced. The resulting hypoxia is known as diffusion hypoxia. Diffusion hypoxia can be prevented by continuing 100% 02 inhalation for a few minutes after discontinuing N20, instead of straight away switching over to air.