The doctors stopped by today to let us know that during an overnight chest x-ray, they had discovered a leak between his lungs and his chest wall. They've switched him from a standard respirator to a "jet" respirator. Instead of the normal 15-20 breaths per minute on the regular respirator, the jet breathes for him at 450 breaths per minute (at a very low pressure). They've also had to put him back on oxygen. Hopefully this will resolve the problem.