From the Guidelines
The Apnea-Hypopnea Index (AHI) and Respiratory Disturbance Index (RDI) are distinct measurements used in polysomnography studies to assess sleep-disordered breathing, with RDI being a more comprehensive measurement that includes AHI plus respiratory effort-related arousals (RERAs). The main difference between AHI and RDI lies in their definitions and the parameters they measure. AHI specifically counts the number of complete airflow cessations (apneas) and partial reductions in airflow (hypopneas) per hour of sleep, as defined in studies such as 1 and 2. In contrast, RDI is a more comprehensive measurement that includes everything in the AHI plus RERAs, which are breathing disruptions that don't meet the criteria for apneas or hypopneas but still cause sleep fragmentation, as noted in 3 and 4.
Key Differences and Clinical Significance
- AHI is calculated based on the sum of apneas and hypopneas per hour of sleep.
- RDI includes AHI (apneas and hypopneas) plus RERAs per hour of sleep, making it a more inclusive measure of sleep-disordered breathing.
- The clinical significance of this difference is crucial for diagnosis and treatment decisions, as RDI may identify subtle breathing disorders that AHI might miss, such as upper airway resistance syndrome.
- Studies like 5 and 6 highlight the importance of considering both AHI and RDI in the diagnosis and management of obstructive sleep apnea (OSA).
Diagnostic and Treatment Implications
- Sleep specialists often consider both AHI and RDI when determining the severity of sleep-disordered breathing and appropriate treatment options.
- Treatment options may include CPAP therapy, oral appliances, or surgical interventions, depending on the severity of OSA and the presence of other sleep disorders.
- The American Academy of Sleep Medicine provides guidelines for the diagnosis and treatment of OSA, emphasizing the importance of polysomnography and the consideration of both AHI and RDI, as seen in 4.
Conclusion is not allowed, so the answer just ends here.
From the Research
Definition of AHI and RDI
- The Apnea-Hypopnea Index (AHI) is defined as the sum of apneas and hypopneas per hour of sleep 7.
- The Respiratory Disturbance Index (RDI) is defined as the sum of apneas, hypopneas, and abnormal respiratory events per hour of sleep 7.
- Often, the two terms are used interchangeably, but they measure slightly different aspects of sleep disturbances.
Difference between AHI and RDI
- AHI only accounts for apneas and hypopneas, while RDI includes additional abnormal respiratory events 7.
- The AHI is widely used to diagnose Obstructive Sleep Apnea (OSA), with different cut-off levels, although the basis for these cut-offs is often unclear or arbitrarily determined 7.
- RDI, on the other hand, provides a more comprehensive measure of respiratory disturbances during sleep, including events that may not meet the criteria for apneas or hypopneas.
Measurement of AHI and RDI
- Both AHI and RDI can be measured using polysomnography (PSG) in a sleep laboratory or with portable sleep study devices (PSSDs) 8, 9.
- Studies have shown that PSSDs can provide accurate measurements of AHI and RDI, with strong correlations between PSSD and PSG measurements 8, 9.
- However, the accuracy of AHI and RDI measurements can depend on the specific device and algorithm used, as well as the presence of other sleep disorders or comorbidities 10.
Clinical Significance of AHI and RDI
- Both AHI and RDI are important indicators of sleep quality and can be used to diagnose and monitor OSA 11, 7.
- Elevated AHI and RDI values are associated with increased risk of cardiovascular disease, diabetes, and other health problems 7.
- Accurate measurement of AHI and RDI is essential for effective management of OSA and related health conditions.