Turning On Pulse Oximeter Sleep Tracking
You can set your watch to continuously measure your blood oxygen saturation, or SpO2, while you sleep (Tips for Erratic Pulse Oximeter Data).
NOTE: Unusual sleep positions can cause abnormally low sleep-time SpO2 readings.
- Hold the touchscreen to view the menu.
- Select
> 
> Sleep Pulse Ox > On > 
.