This afternoon, in a plseant 72F/65%, enjoying a cup of coffee with a friend.
Feeling slightly SOB, I checked my O2, on my thumb as I usually do. 84%! I turned on the O2, and watched it bounce around 84%-87%. I then increased the O2 to #3, still below 88%.
I moved it to my finger, and it jumped to 90%!
I couldn't get O2% above 88% on my thumb, yet it was fine on my finger!
Once I got into the house, with A/C both finger and thumb were reading normal low 90%'s.
Also when in the car, or pushing a grocery cart, I either get no reading or it takes several minutes.
Other times it will report extremes, say 98% or 84% - hence the question when do you trust the meter?
Sorry for all these questions.