Your mother really had a ad flare up of COPD.
The drop in oxygen and relative rise in CO2 is consistent with respiratory acidosis --very typical with respiratory failure associated with COPD.
her respiratory muscles are weak and not able to get in enough oxygen resulting in this problem.
Bipap was a good decision and then switch to CPAD was even better.
CPAP allows to force in the oxygen against the airway resistance with little effort from the patient.
Hence, your mother has shown remarkable improvement in terms of blood gases.
She should be ok with hospital discharge as long as she is using CPAP daily at home without fail.
That will help her to recover over time.
Short hospital stay is favored to prevent contracting any resistant infection which in your mother's case can be more serious.
It was my pleasure to help you today.
If I have answered all your questions, Please rate my response Excellent (click on the smiley faces) under this chat box only.
Please bookmark my profile for asking further questions!
This is the link to my profile: