I have A fib and had the same thing. I take one by cuff and one by Pulsox however there is a little change. It is mostly AFib that makes it change......Take it when you get up and anytime you feel as though you are SOB or that you are overdoing.

If you have afib that's not controlled or anything that affects the circulation of your hand you will get erratic readings. Nail polish can also cause false readings. Basically any oximeter will do. I got mine from Amazon. (Metene) works great. Warm hands. Try it on both hands same finger. Correlate it with your heart rate. And keep track by writing it down. The numbers will fluctuate give it about 10 seconds to read your body.
You should start to see a range for you.
Good luck!!
Ps you see the PI%---THAT IS PERFUSION INDEX. LETS YOU KNOW IF YOU ARE GETTING A DECENT READING.

Psliger
The pulse oximeter will work backwards also and won't matter if you have nail polish. Place it on the fleshy side. Try it!!
And I tried it on my toes, because some on this site have raynaud's and fingers don't work. I should have vidioed it. Contortionist extraordinar! 🤣

I was right! Spendy, did you try the download idea Psliger talked about above? Especially if it's free!

My daughter found a program on our phones that shows rhythm and pulse. To be honest weve compared it to the monitors at the hospital there really close. The program was free. It even shows when shes in afib. Check out your store on your phone. You might have to check several to find a good one. If you have a program that you can comunicate with your doctors you can even save the rhythm to your phone and send it to your doctor. Just like this. No that is not good newd. She sent that to me at work. Not nice to do that to mom.