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Oximetry results explainer

Overnight oximetry reports are a page of numbers with no explanation. Type in what yours shows, from a clinic, a ring, a watch or a finger oximeter app, and see each figure against published reference ranges. Nothing you enter is sent anywhere.

Enter whatever your report gives you

Leave anything it does not show blank. Each figure is interpreted on its own, and the overall message comes from the most concerning one.

Called ODI, oxygen desaturation index, or sometimes "drops per hour". Choose 3% or 4% to match the report.

Also called the nadir or minimum SpO2.

The mean across the whole recording.

Often written T90 or "time under 90%". If the report gives minutes, divide by the length of the night in minutes.

Optional context. It never changes the overall verdict on its own.

Optional. Indices from under 4 hours of sleep are unreliable, and this will say so.

Where to find the numbers

  • Desaturation index. Written ODI, ODI3, ODI4 or “drops per hour”. Wellue’s ViHealth app calls it “O2 drops”.
  • Lowest SpO2. Labelled minimum, nadir or lowest.
  • Time below 90%. Enter a percentage. If your report gives minutes, divide by the recording length in minutes and multiply by 100.
  • A clinic report also carries an event index from the sleep study itself. No oximeter can produce it and this page does not interpret it.

Why the bands are what they are

  • Desaturation index. The lines at 5, 15 and 30 events an hour come from the cut points the American Academy of Sleep Medicine publishes for a sleep study’s event index. An ODI tends to run a little under that index. Home oximetry is not a sleep study.
  • Lowest SpO2. Blood oxygen falls away faster below 90%, which is why 90 is the line.
  • Average SpO2 and time below 90%. These describe the whole night, not single events.
  • Average pulse. Context only. It never changes the overall result.

If you have the recording, not just the report

Our free session viewer reads a Wellue CSV or pulls a night off the device, charts it and adds figures most apps leave out, such as the longest event. The blog post on ODI covers what it counts and the published bands.

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

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