What Is ODI? Oxygen Desaturation Index
ODI is how many times an hour your blood oxygen dipped and recovered. Here's what it counts, 3% versus 4%, and how to compare your nights.
ODI stands for oxygen desaturation index. It's the number of times per hour your blood oxygen (SpO2) dipped and then recovered. An ODI of 5 means about five dips for every hour you recorded.
How is it worked out?
Count the dips in the recording, then divide by the hours recorded. Dividing by hours is what lets you compare a six hour night with a nine hour one.
Not every wobble is a dip. A drop has to be deep enough and last long enough to count. The exact rules are in what counts as an oxygen dip.
What's the difference between 3% and 4%?
It's how far your oxygen has to fall before the drop is counted.
- ODI-3% counts drops of 3 points or more.
- ODI-4% counts drops of 4 points or more, so it's always the same or lower for the same night.
They're two different measurements. Only compare numbers that use the same threshold and come from the same app.
Where do 5, 15 and 30 come from?
You'll see these three numbers quoted a lot. They come from a 1999 American Academy of Sleep Medicine task force report, which set cut points at 5, 15 and 30 events per hour. Those cut points are for breathing events counted in a laboratory sleep study. ODI from a ring is a different measurement, and home oximetry is not a sleep study.
PulseOxTracker uses the same lines to label your index low, elevated, high or very high. The label describes the measurement. It says nothing about what caused the dips.
What can throw it off?
- A loose ring. Bad contact can add dips that didn't happen. See why your O2Ring data has gaps.
- One odd night. Your ODI changes from night to night. Here's how many nights to record before you compare.
ODI also misses long, shallow stretches of low oxygen. T90 covers those, so read the two together.
If you use CPAP, your machine's event count comes from airflow, not oxygen, so it won't match your ODI. There's more in tracking your oxygen alongside CPAP.
What can you do with it?
Record 5 ordinary nights first. Then change one thing, keep it up for two weeks, and compare. These posts walk through four things you can test:
PulseOxTracker works out ODI-3% and ODI-4% for every night and lets you tag what you changed. To check one recording without an account, open it in the free session viewer. Only have an event count and a recording length? The ODI and T90 calculator does the division.
When should you see a doctor?
Book an appointment if your ODI is elevated or higher on most nights. Do the same if you snore loudly, someone has heard you stop breathing or gasp, or you're exhausted during the day. A snoring app and an oximeter record different things, and this post compares them. Before you go, read how to share your oximeter data with your doctor.
Not a medical device. Does not diagnose, treat or prevent any condition. Discuss results and changes with a clinician.
References
- American Academy of Sleep Medicine Task Force. Sleep-related breathing disorders in adults: recommendations for syndrome definition and measurement techniques in clinical research. Sleep. 1999;22(5):667-689. doi:10.1093/sleep/22.5.667