About two weeks ago with my daytime unassisted SP O2 at 88-94% (4,500 feet above sea level) I went to bed with my O2 set at 2.5 LPM. Nothing remarkable, except that the following mornings I noticed a rapid 2 minute drop into the 70's (previously mid-80's over a period of about 5 minutes) and taking 20-30 minutes to come back up into the low 90's unassisted. Typically I awake in the 95-97 range and this was still the case. This deeper morning drop off gave me the idea that (1) my assisted O2 upon awakening was running a bit high and (2) my body was becoming lazy about making itself breathe as O2 was too available/plentiful. When I was originally sleep tested at 63% lows, with an 81% avg. my doctor prescribed 3 LPM. My O2 was 97-99% at spot checks which was not comfortable, and was also on pure O2 (99.8%/bottled), I had become settled at 2.5 LPM on my O2 generator (97% O2) for months.
I reduced my LPM to 2.25 for a couple of nights with about the same morning results. Dropping it again to 2.0 for two days and then 1.75 for two more. My morning drop off started to ease. Low 80's for about 15-20 minutes and back into comfortable low 90's. Two days later I dropped the LPM setting to 1.5. That resulted in (assisted O2) overnight spot checks still in the 92-94 range, and the morning drop off to mid-80's with about a 10 minute recovery to my normal lower 90's. Intuitively, and I'm asking for anyone to comment, it seems that too much O2 had "spoiled" my (bronchial/emphysema) damaged lungs and they were not "waking up" like they had been doing for months once I got out of bed (off the hose).
Last night, with my setting at 1.5, I awakened after three hours sleep with very short breath, but I tested at 93. Managing the anxiety was difficult. I was without a solution until I took a quarter of a viagra 200 mg tablet. I had used an eight to a quarter tablet to periodically boost my unassisted O2 when doing heavy lifting/long duration welding (with an air filtered hood/PAPR). My very shallow breathing started to ease about 15 minutes later and as I laid down with my 1.5 LPM, my depth of breath opened up and I have not had such wonderful easy breathing in nearly three years! Still assisted, I tested at 94-95% two more times during before I got out of bed. My drop off went only to the mid-80's and was back to 92-93% within 5 minutes. Any ideas out there? I've read where viagra was originally a pulmonary directed development, and have used it about 2 dozen times at about 50 mg with a good result of an added 5-8% to my unassisted O2 reads for 3 or 4 hours. Notably, I am still drawing air with that full breath feeling this morning 8 hours later. If you've had this experience or heard of anything like this, I'm very interested. Here in the USA, our health care system is so corrupted by greed, I don't even want to bring this latest event up with my doctor. I'll end up paying out another $140 US for the office visit, while I continue to pay my $498 a month " health insurance" bill. I can buy viagra overseas for a dollar a tablet (not $10 each here in the US). That's 25 cents a night or 560 doses at 50 mg at $140! Last year I spent nearly 11 thousand dollars on health care...and last night a 25 cent dose of viagra rocked my world. I'm very interested. Though I'm not a conventional medicine mentality and herbal oriented/Non GMO type, I'll compromise given continued results like this can be achieved.
low oxygen levels
Good sats - so why so breathless?
O2 levels
Losing weight with Viagra. 
Middle of the night terrors
