SpO2 data from an Apple Watch (or any wrist device) is highly suspect and not reliable as a diagnostic tool. Under ideal conditions it can work reasonably well

SpO2 data from an Apple Watch (or any wrist device) is highly suspect and not reliable as a diagnostic tool. Under ideal conditions it can work reasonably well but it can also be thrown way off by multiple factors like wristband tightness, skin color, patient movements, dirt, etc. A cheap and simple dedicated pulse oximeter that clips on to your finger will generally be much more accurate and consistent.