Oxygen at home

For issues specific to caring for someone with dementia.
Hi - Any one out there that can throw a bit of advice.

My mum has always had low oxygen levels and after a recent spell in hospital with a chest infection she was discharged with oxygen at home 1.5 litres 16 hours a day.
A follow up visit from a respitory nurse has resulted in her advising to up it to 2 litres 24 hours a day.
My mum has Parkinson’s dementia and since coming home with oxygen her moods have changed so much.
We ruled out a urine infection but she is now incredibly tired all the time and confused. She is aggressive in the mornings and because she is blind she wildly lashes out which I know is not her fault.
I’m sure she is now overdosing on oxygen and retaining CO2 but the nurses don’t seem that bothered with her behaviour.
I’m going to try our GP first but really want to bypass the respitory nurses who don’t see the “dementia” side of my mum and speak to the respitory consultant who was great with mum
Anyone else ever had CO2 issues ?
I can't answer in the slightest over ODing on Oxygen (or on retained Co2), but I'm wondering whether YOU can manually 'fiddle' the feed at all, so that she is getting a little less O2???? Just a bit to start with, and 'see what happens'. If you see her agitation easing off, that would give you a clue. Conversely, if you see her starting to struggle for breath, then you will know that she CANNOT do without the prescribed dose of O2, and that is that, alas.....