hyperventilation
A mate of mine made an emergency descent after a Trident cabin decompression in the 1970s.
The next day he checked in but felt a little bit unwell so he went over to BA medical service who sent him home. He then went to his GP who sent him to hospital.
He underwent an emergency procedure for a collapsed lung later same day which saved his life.
Amazing what can happen to aircrew if they hyperventilate.
Absolute disgrace which seems to be still happening.