Do you grade severity of OSA by AHI or RDI?

We recently changed, per AASM guidelines, to reporting both AHI3a and AHI4. Since most sleep-disordered breathing events will qualify with the 3a decision, as it includes arousals, we have stopped reporting an RDI. If there are events that don't meet the 3a hypopnea definition, we might comment on it in the interpretation but currently are not quantitating as RERA's.

Let's first agree on the basic definitions:

AHI: Apnea hypopnea Index:

• Apneas: Complete cessations (>90%) of airflow lasting for at least 10 seconds.
• Hypopneas: Partial reductions (>30-50%) in airflow leading to a decrease in oxygen saturation (by at least 3% or 4%) or arousal from sleep.
• AHI = (number of apneas and hypopneas)/total sleep time in hours.

RDI: Respiratory disturbance index:

• Includes Respiratory effort-related arousals (RERAs): episodes of increased respiratory effort leading to arousal from sleep but do not meet the criteria for apneas or hypopneas.
• RDI = (number apneas, hypopneas, and RERAs)/total sleep time in hours

So this question comes down to, do you "believe in RERAs"?

While there is physiologic evidence that RERAs...

While 3% and 4% hypopnea and apneas as well as RERA are useful they are flawed in patients with long apneas. For instance, someone who has one-minute apneas can have an AHI of 60/hr while someone with 30-second apneas can calculate to 120/hr. Clearly, the 1-minute apneas are more severe and the AHI suggests otherwise. What we need additional parameters to record to rectify this problem. I suggest Total Apnea Time (time spent with no airflow) over Total sleep time.

AASM goes by AHI.

AHI.