ODI-4 (Oxygen Desaturation Index, 4%)
The number of times per hour blood oxygen drops by 4% or more. Uses a stricter threshold than ODI-3, capturing only more significant oxygen desaturations.
What Is ODI-4 (Oxygen Desaturation Index, 4%)?
The Oxygen Desaturation Index at 4% threshold (ODI-4) counts the number of times per hour that blood oxygen (SpO2) drops by 4% or more from a 2-minute rolling baseline. The 4% threshold is the criterion most commonly used in clinical sleep studies and aligns with the AASM (American Academy of Sleep Medicine) hypopnea scoring criteria.
ODI-4 is typically lower than ODI-3 because it requires a larger oxygen drop. This makes it more specific to clinically significant events but less sensitive to subtle desaturations. When ODI-3 is significantly higher than ODI-4, it suggests many events are causing moderate (3-4%) but not severe (4%+) oxygen drops.
In the context of PAP therapy, an elevated ODI-4 while on treatment warrants clinical attention, as it suggests the current therapy settings are not adequately preventing oxygen desaturation events. AirwayLab reports both ODI-3 and ODI-4 to give a complete picture of desaturation severity.
Normal Ranges
How AirwayLab Measures This
The Oximetry Pipeline computes ODI-4 from Viatom/Checkme O2 Max CSV data using a 2-minute rolling SpO2 baseline. Each drop of 4% or more is counted as a desaturation event. Reported alongside ODI-3 on the Oximetry tab for comparison.
Try it with your dataFrequently Asked Questions
Which is more important, ODI-3 or ODI-4?
ODI-4 aligns with standard clinical scoring criteria and is the more commonly cited index. ODI-3 is more sensitive and captures subtler desaturations. Both are useful: ODI-4 for comparison with clinical reports, ODI-3 for a more complete picture of breathing disruption.
Related Terms
Medical Disclaimer
AirwayLab is not a medical device and is not FDA-cleared or CE-marked. It is provided for educational and informational purposes only. The analysis results should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always consult qualified healthcare providers regarding your sleep therapy and any changes to PAP settings.