Belly breathing on PC.

Hello, first time posting on here sorry if it’s all over the place lol! New grad RT here with a question. Had a patient who was found to have intentionally overdosed on antidepressants. Intubated for airway protection and eventually was switched from VC to PC. I received the patient and was given a VERY brief and vague report (pretty much just vent settings and tube placement, even after asking for more details about the pt) so when I went up I was surprised to see the patient breathing in the 40’s and belly breathing. Looking back on previous charting it looks like he’d been doing this since at least that afternoon (night shifter here) and was not told about it. I adjusted their inspiration pressure, insp time, and even trigger sensitivity. The patient is already on quite a bit of sedation, and bolusing this pt didn’t seem to do much. I work at a small hospital with only 2 RT’s on nights and am stuck on what I could have done differently! Any input is appreciated! Thank you all! (-: