AHI or RDI?

I recently had my first time sleep study for Sleep Apnea. So they did the first night where I stay at the sleep center overnight. They were supposed to put me with a CPAP during the middle of the night if I had enough signs of sleep apnea within my very first hours. However, the didn't. In the morning they told me that I have sleep apnea. And asked me to comeback in another day to do the whole overnight study with the CPAP machine. After my second night study they set me up with the machine I should be prescribed to use etc. But when I went over in the test results...

On the first night-sleep study: I had a RDI overall index of 23.5 On the second night-sleep study with the CPAP machine: I came up with an overall index RDI of 17.3

However, on the the second study results they framed on the history as AHI of 23.5, not RDI. I understood always that the RDI score differs from the AHI score. What would be the case in this assessment?

AHI is the sum of all central events, obstructive events, and hypopnea events divided by the number of hours of sleep. RDI is the same thing but RERA (respiratory-effort related arousals) events are also added in. RDI is always equal or greater than the AHI. Not all health care organizations accept the significance of the RDI number. Sleep apnea is diagnosed based on a minimum AHI of 5. You cannot compare an AHI or RDI taken while using a CPAP to one taken during a sleep test. The treatment pressure of the CPAP will change the AHI (down hopefully). No pressure is used during a standard sleep test.

Correct, thanks for the reply. Why do you think they placed the test result as AHI when the actual study results shows it as RDI? From your standpoint and experience

Well I was processing a physical for warrant helicopter pilot with the Army. They use the AHI score for considering medical waiver if needed based of the AHI score. But then, the Civilian doctor put on the remarks for the second part of the sleep study that my AHI score was the one I had for the RDI on the first night study I did without CPAP. The reason I'm researching on my own is to understand if there was a discrepancy or inaccuracy in the testing process for them to make the diagnosis. Thanks again.

I guess some are now, cause my sleep study results is all in RDI numbers. But I was assuming that they placed the RDI number as AHI for the same reason you mentioned before without knowing how affects me career wise.

Can you get them to restate the diagnostic study in AHI, since that is the metric used by the licensing authority? And is this in the US?

Correct, but they did place the same RDI score I got in the first sleep study equal on the second result as ASI. Which is questionable of them making comments on my medical records with a score from a different equation.