I use a pulse oximeter because it is more accurate in monitoring my heartrate than smartwatches or fitbits I’ve tried. I noticed that my oxygen saturation fluctuates a lot during the day, everyday. It goes from 90-99 spo2. Especially on waking I have lower O2 values. (91-92) It’s not the meter, they are very accurate; whenever I test it on my wife or son they always have 98-99. I cant find a relation with activity or the way I am feeling. It’s just 9% below optimal sometimes. And everyone else I test it on has 98-99. No asthma, Copd or anemia. Could this be caused by poor circulation to the extremities? Is this a common thing in ME or dysautonomia?