We are trained to recognise hypoxia over the airwaves, and how quickly it can set in at different altitudes. But we can't know what's going on in the cockpit if we aren't told. If the pilot realised he had a pressurisation problem then he should have descended without clearance, and, if he had time, squawked 77 and told ATC.
If separation is lost due to an emergency, we face no sanction, and are permitted to use 500 ft emergency vertical separation if warrated