Having used ketamine a lot...and for this purpose, I'm sold. Do you really need a study to back up common sense in this instance? If you have a respiratory patient who is toeing the line of respiratory arrest, do you really want to risk making them worse? Disassociate them. They'll either get better on BiPAP or they won't. It won't be the fault of the ketamine if they don't. If they don't, drop your tube and move on.