This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anaesthesia
Diffusion hypoxia is seen during – 
Select and explain. 
A. Induction of anaesthesia, B. Recovering anaesthesia, C. Preoperatively, D. Postoperatively
B: Recovering anaesthesia
Answer: B: Recovering anaesthesia 
Explanation: Concentration effect and secondary gas effect → During induction.
Diffusion hypoxia → during recovery.
All these occurs with N2O only. (Now anaesthetic gas xenon also produces all these effects).