Any advice on how to help my mother put on her oxygen and keep it on throughout the night?

If it were me, I'd leave her alone. With advanced dementia & all the rest of the serious health issues your mother is suffering, trying to prolong her life sounds like a mistake. But that's just my opinion based on my own end of life wishes. And based on seeing how miserable my own mother is with dementia and chronic pain, etc. etc. Forcing care on someone who doesn't want it seems over the top to me.

Wishing you the best of luck in such a tough situation

Hi Bigcasey
How old is your mom? Your bio says she is 72.
The fact that she is combative would make me back way off. I suppose any calming medication might be counterproductive to breathing.
I suspect I will have the same problem with DH Aunt, 94 with dementia. She recently received oxygen through hospice to have on hand. She wasn’t feeling well last week and I decided to check her vitals around 8 pm. I was shocked to find her O2 was in low 80s, high 70s. We check it each morning and it’s always great. It kept fluctuating that night. 82 to 97. That sort of variation. She’s recently gone on Medicare hospice and I was able to speak with a nurse and make a decision to let it go with regular checks. We received oxygen the next day but I doubt she will leave it on if and when it’s needed. She has had no seizures. It’s not gone below 95 since then on morning checks. When my MIL was in a hospital facility on hospice, she kept removing hers. Her daughter would replace it. MIL finally told her daughter “if I die, I die”. She wanted it off. She did die but it was from her cancer not the lack of O2.
It’s good to have all the info you’ve gotten on the tape etc.
I would call hospice if you haven’t already. The Medicare rules are now such that If her dementia isn’t reversible, she would qualify. You might find their assistance helpful.
Let us know how she’s doing.

How ill is your Mother? Has your Mother completed any life directives? Specifically, do you know how much intervention she is willing to accept?

O2 is a simple therapy that can offer better quality of sleep & breathing but it sounds like her health issues may be quite serious & that 02 is only part of the problem?

For those with sensitive skin we used to use tegaderm placed first on the skin; it can actually be protective. The the cannula put on a paper tape over the cannula and attached to the tegaderm, not the skin. It can still be a problem with picking during the night. It's a difficult problem.

I have seen hospitals tape it to the face of patients that remove it.

Have you tried that?