I've herd that smoking raises the O2 readings. I know wet hands appear to dramatically lower O2 readings. This morning, after carrying the junk out {snow on the ground, 30F} I was SOB, on both trips to the curb, did PLB to restore myself. Also it was time for a puff of Combivent, which I took. But, when I sat down, with some PLB, I took a reading; O2=77, pulse 111! very alarming! I then warmed up a finger, and got a more reasonable reading after a couple tries, settling in at O2=92.
ed