Heres an easy explanation. Assist control is the vent doing the work but the patient can take his own breaths.
CPAP is a weaning mode where the patient is breathing on his own but the vent will kick in if needed. Signs of weaning failure: high respirations
Those are the only settings we use in our unit.
Alarms: High pressure is when the tube is occluded somewhere from biting, plugs, mucus, and if all else fails the filter between the the tubes.
Low pressure is when something is off, or leaking.
Thats all we nurses worry about in our unit, the rest Respiratory takes care of.