A kink in the line.

Max has great lungs. They know what to do, and they work hard at the whole "breathing" thing. Regardless of that, his throat refuses to allow enough air into them so that his body can work at its optimal level.  They tried to extubate him today. He struggled too much with getting in enough oxygen - again, his lungs were doing the right thing, there was just a physical blockage preventing them from getting enough of a flow going.  In the end, they had to re-intubate him. He had a long day.