O2Ring vs Checkme O2 Max vs SleepU

Wellue sells three overnight oximeters. All three record your SpO2, pulse and movement every few seconds while you sleep, then sync the night to the ViHealth app. They differ in how you wear them and how long they run.

Specs change between hardware versions, so check the listing for the exact model before you buy.

What's the short version?

• O2Ring. A ring. No wrist unit and no cable.
• SleepU. A wrist unit with a soft finger sensor on a short cable.
• Checkme O2 Max. The same wrist and sensor layout as the SleepU, with a bigger battery.

Which is most comfortable?

That depends on your fingers and how you sleep.

• The ring has nothing to snag. The sensor, battery and memory are all in the band.
• The ring only fits a set range of finger sizes. A loose ring shifts in the night and leaves gaps in the recording. Check O2Ring sizing first.
• The finger sensor is adjustable. It fits fingers the ring won't.
• The cable can catch on bedding. Some restless sleepers mind that more than a loose ring, and some mind it less.

For the wrist models, see our SleepU tips and Checkme O2 Max tips. For rings against other shapes in general, see ring vs fingertip vs wrist.

How long does the battery last?

All three cover a full night.

• O2Ring and SleepU. Plan to charge them every day.
• Checkme O2 Max. Built to run for several nights on one charge.

That matters if you're away from a charger, on a trip or recording a long flight.

Each device only stores a few recordings. Sync every morning if you can. If you can't, check the listing for how many nights your model holds.

Do they all have a vibration alert?

Yes. Each one can buzz when your reading drops below a level you set. It's a nudge, not a safety monitor, so don't rely on it to wake you. It also changes the night you're recording, so keep it either on or off for all the nights you want to compare. More in should you use the vibration alert.

Is the data different?

No. Every model exports a night from ViHealth as a CSV file with the same four columns: time, SpO2, pulse and motion. The gap between samples is 2 or 4 seconds, depending on the model. The CSV export guide explains the file.

So you aren't locked into one device. Nights from a SleepU this year sit on the same trend as nights from an O2Ring next year.

Which should you buy?

• You want nothing on your wrist: O2Ring, if the size fits.
• The ring won't fit your fingers: SleepU.
• You'll record several nights away from a charger: Checkme O2 Max.

To rank them against your own priorities, try the free overnight oximeter picker.

Whichever you pick, one night won't tell you much. How many nights to record explains how many you need before you compare anything.

Not a medical device. Does not diagnose, treat or prevent any condition. Discuss results and changes with a clinician.