Questions:
1. Reading Euro Control ACAS bulletin 9 it says set Transponder to TA Only. This is because you are performance impaired and do not want an RA to opose the Emergency descent.
2. Following good CRM practices, whereby you include ATC in the loop, would you declare a MayDay and request a descent clearance, or just throw a dropping brick onto ATC radar screens who would then scream at you to maintain level? You would then have to explain why you are dropping out of the sky. Why not emply good teamwork and wait a few seconds. No-ones going to die form O2 starvation, but they might from a rushed procedure and ATC confusion.
What do you do SOP? What do you Think, Airmanship?
Given the apparent differences in ATC regions, might not including ATC in your intentions be a sound idea?