Ditto what GrnTea said. If you're going to do a respiratory care plan, you need more nursing assessments that support whatever diagnosis you come up with. You mentioned some physical assessment, but what about other types? By that I mean vitals, labs, diagnostics, medications, IVs, wounds, I & O, diet, medical history, patient's chief complaint(s) etc. What is her pulse ox? I know that you auscultated her lungs, but did you observe
the patient breathes? Purse-lipped, use of accessory muscles, etc. ?
The medical diagnosis definitely helps identify potential nursing diagnoses. I almost always use medical dx to look up potential nursing dx in my care plan book by Ackley. Ultimately though, it will be your
assessments, observations, and conclusions that back up the nursing diagnosis.
Based on what you told us it sounds like Impaired gas exchange is a good nursing dx for this patient, but you have to know why (r/t)
gas exchange is impaired and then prove it
by showing how you know (aeb)
gas exchange is impaired (aka EVIDENCE). I find it helpful to briefly review the A&P and patho. Gather all of your data, pick out what is abnormal, and then match it to the manifestations of the disease process.
You also mentioned psychosis and how you would incorporate that into a respiratory care plan -- I would ask myself: how does the patient's mental status relate to her respiratory problems? Lethargy, confusion, agitation...these are all are good indicators that patient isn't getting enough O2 = evidence of impaired gas exchange.
Sorry for all the rambling thoughts. This is just how I would approach this patient and care plan. I'm only a soon-to-be 3rd semester nursing student, so I hope I was able to help at least a little!