There has been some concerns with oximeters in general because oximeters read O2 saturation levels by shining light through the skin (it's actually more complicated than that, but you get the point.) They are not as accurate if you are dark skinned for this and for other reasons. O2 saturation is most overestimated at low saturation levels (where O2 levels really matters.) The darker you are, the greater the effect. Ink, nail polish and other substances on the skin have also been documented to affect readings in everyone. The degree of effect varies across different brands of clinical oximeters. Here's an article in Boston Review just last month that emphasizes the social implications. Here's an article published by The American Society of Anesthesiologists in 2005 that is more technical and analytical in nature (but it's still very readable.) Just thought I'd throw this out there for everyone's info. This may not be so widely known in the medical community, and with all the virus stuff going on, it's important to be aware that marginal O2 readings in a clinical setting might actually be lower than are indicated for some of us and those we know. There are other ways to get this data that involve lab work.