Would some sauropods need to maintain blood flow in order to raise their heads long enough to take a mouthful? Surely if a diplodocid (or other species that maintained horizontal necks most of the time) was able to seal off the blood supply out of the neck for a few seconds to prevent blood from draining away from the brain, then a few moments of no blood flow to that tiny brain wouldn't be so critical?
It would mean they couldn't raise their heads for any length of time (barring other unknown blood flow mechanisms), but it wouldn't make quick forays into higher elevations entirely impossible.
That's Bakker's hypothesis, but I don't know how long even a small brain could function without a constant oxygen supply. It would mean that these
Would higher oxygen levels compensate?