I'm going to append this in case someone might be
desparately googling for answers
The first 3 instances of collapse my dog was crying out
loud for help (very hard to take!). But the subsequent 4 or 5
events he didn't, he just laid there motionless so my hunch
is that initially he was really panicking in a world of darkness,
dizziness and who know what but then he got used to the
sensation. This, anyway, would be a better situation than
one of excrutiating pain.
I'm no vet so I don't know!