RDI (Respiratory Disturbance Index)
The total number of respiratory events per hour, including apneas, hypopneas, and RERAs. A more comprehensive measure than AHI alone.
What Is RDI (Respiratory Disturbance Index)?
The Respiratory Disturbance Index (RDI) is a comprehensive measure of breathing disruption that includes all respiratory events: apneas (complete airflow cessation), hypopneas (significant airflow reduction), and RERAs (effort-related arousals). By including RERAs, RDI captures a fuller picture of sleep-disordered breathing than AHI alone.
The difference between AHI and RDI can be dramatic. A person with an AHI of 3 (normal) might have an RDI of 20 (moderate-severe) if they have frequent RERAs. This distinction is especially important in Upper Airway Resistance Syndrome (UARS), where AHI looks normal but RERAs are fragmenting sleep.
AirwayLab estimates RDI by combining its RERA detection (flow-limited breath sequences terminated by recovery breaths) with hypopnea detection (sustained flow amplitude drops). This estimated RDI provides a more complete picture of breathing disruption than the machine-reported AHI alone, though a full clinical RDI also requires EEG-confirmed arousals.
Normal Ranges
How AirwayLab Measures This
AirwayLab estimates RDI by combining detected RERAs (NED engine) with detected hypopneas (flow amplitude drops sustained for 10+ seconds). Apneas cannot be reliably detected from flow data alone, so this estimate is a conservative lower bound. It is most accurate when apneas are rare, as is typical in UARS.
Try it with your dataFrequently Asked Questions
What is the difference between AHI and RDI?
AHI counts only apneas and hypopneas. RDI counts apneas, hypopneas, and RERAs (Respiratory Effort-Related Arousals). RDI is always equal to or higher than AHI. The gap between them reveals how many breathing disruptions are being missed by the standard AHI metric.
Why does my estimated RDI differ from my in-lab RDI?
AirwayLab estimates RDI from flow data alone. In-lab RDI uses EEG to confirm arousals and has access to additional signals. AirwayLab's estimate is a conservative lower bound because it cannot detect apneas from flow data and relies on respiratory patterns to estimate arousals that normally require EEG confirmation.
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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.