I've been reading about this as I have COPD and PN, was told for 4 years it was idiopathic.

They don't seem to know much about it yet, they have discovered a good % of people with COPD have sub-clinical PN, fewer have symptoms. Possible causes I've seen have been hypoxia, hypoxemia, nerve damage from the nicotine and toxicity from meds used to treat it. My PN is worse at higher doses of inhaled steroid. Some studies have shown that the length of time a person smoked was more predictive of PN than hypoxia.

That said, I think if your O2 sats dropped low enough to cause a problem you'd probably wake up or feel some effects in the AM. The point at which they feel there is tissue damage is O2 saturation of 88% normal, people with COPD can drop into the 60s and 70s.

I've been sleeping with my head covered up as long as I can remember, of course I do have PN..lol
Zygo