if my pulse/oxygen fingertip device works on my friend, why doesn't it work on me

[Pattarada]

I finally got the finger tip device to register, but it measured my blood oxygen level at 76?That seems dangerous. I am very short of breath unless I walk slowly with nothing in my hands. My BP on the OMRON device was 111/75

[GoodGrief1]

I'm no expert, but can relate a couple things I've noted.  My pulse ox works best when my hands are warm.  My forefinger is skinny, so I measure my second finger.  My hands need to be no higher than my heart.  I use a Nonin pulse ox.  It works well.