I was the CTO of a healthcare company that focused on patients with heart failure. We did buy a bunch of "non-medical use only" O2 saturation monitors during co

I was the CTO of a healthcare company that focused on patients with heart failure. We did buy a bunch of "non-medical use only" O2 saturation monitors during covid because it is all we could get our hands on. They're notoriously unreliable and variable compared to something that doesn't have a CLIA waiver. Since you have family with heart failure, I'd highly recommend you acquire a more expensive device to get the most accurate readings. Also change up which fingers you use as that tends to drive differences in SpO2 (at least on my personal experimentation with the cheap SpO2 monitors)