In order to see Spo2 you'll first need to select the Fitbit Spo2 clock face before you go to sleep and keep it active the entire time you're asleep. When you wake up, the Sense will need to sync to the app and even after syncing it seems to take 30 minutes for the clock face to show the Spo2 %. The Spo2 variation though will show up with your sleep score towards the bottom of the detail page in a graph. Having to select the clock face and not having on demand Spo2 is really annoying. Vote on these 2 feature requests to see if we can get Fitbit to change this: https://community.fitbit.com/t5/Feature-Suggestions/View-SpO2-in-app-and-don-t-require-SpO2-clock-fa... and https://community.fitbit.com/t5/Feature-Suggestions/Check-my-Sp02-pulse-ox-at-anytime-on-supported-F....
