Just heard on the news that the pilot requested lower altitude twice but the controller said "I'll get back to you".
However, if the situation was an emergency , he should have declared it and the controller would have turned the airspace over to him.
That fact that the pilot wanted a lower altitude suggested an air problem. But, he only asked to go down to 18,000. If he need oxygen quickly, he should have hurried down to about 4,000 and opened the outside air ventilation.
It could have been that he was already impaired some, a condition that will deteriorate you cognitive skills. He might not have realized that he was only moments from fainting. The controller had no way of knowing that the pilot was about to pass out.
This was a tragedy that shouldn't have happened.
If the plane had been equipped with the avionics I described, the controller could have directed to autopilot to turn over the controls to him and the plane could have either been landed automatically or sent into a holding pattern and a lower altitude in hopes that the pilot or passenger would have regained consciousness.
Think about the John Kennedy , Jr. crash off of cape cod several years ago. He could have called the controller and turned his autopilot over him. The controller would have brought him back to Boston where Kennedy should have been able to take over and land.
By the way, if Kennedy had just thought about it, he could have set up his autopilot to take him back to Boston where he could landed, saving his and his wife's lives. That flight was a case of terrible airman ship on Kennedy's part. He should hot have been allowed to solo, let alone carry passengers.