Here's what my doc said about the dangers of pressure being too high. First, if you have any heart or lung disease it will make that worse. It can cause central apneas. It will make the sleep apnea a lot worse in general. Any bloating, etc, is not dangerous, just damned uncomfortable. Nothing about blood on the tongue or back aches. Your chest and stomch may hurt, but that is also not dangerous. You most likely will wake up feeling lousy. IF the pressure feels to high even tho it was prescribed from the sleep study, he recommended to contact your DR for further follow-up. Some people do need pressures that they think are too high, but that's the only way to control their apnea. Other than the heart, lung and central apnea issues, there isn't as much danger as what I originally thought I heard him convey. If you're healthy, the very real possibilities is the central apneas.
Peter