Ok, this is plain weird, hard to explain and absolutely subjective, but I've had some interesting "visions" (mind you, I've never had severe delirium of high fevers in my life, but I can remember some bad nights
when I was I child and had big colds.
The main theme of the "nightmare" is one of distance. I can feel enormous distances inside my mind. It's like navigating with the mind without moving (no flying dream), like having a macro and a zoom together, having a sense of hollowness (I made a joke! my head is empty!) and stillness.
One interesting thing is that with a little of effort and depending on my mood, I can feel a very soft version of these sensations when I am in bed trying to sleep.
This is the first time I try to put in words those feelings. As Hal used to say:
"I feel much better now"