"Blood that remains in the brain too long creates a delay in deoxyginated blood leaving the head ("slowed perfusion"). This can cause hypoxia, a lack of oxygen in the brain. Plasma and iron from blood deposited in the brain tissue can also be very damaging leading to iron along with other unwelcome cells, to cross the crucial brain-blood barrier."
I've sent a communication to ask what Professor Philip James (Our specialist Oxygen Therapy Adviser) thinks about the idea. I will publish his thoughts on the blog as soon as I hear back from him.