I'm really worried about my 63-year-old mom. She has COPD bronchitis and has been on medication for a while now, like using a nebulizer and inhalers. We just got her X-ray done, and it said there are fibrotic changes in RV2, but everything else is normal. At home, she's on oxygen all the time, and her levels on the oximeter show between 92 to 98 when she's using it. But as soon as we take off the oxygen, it drops to 60 or 70. Her COVID test came back negative, but I don't understand why her blood oxygen levels aren't improving. Could you please help us understand what's happening and what we should do next?