AHI vs RDI?

[lvillanueva5]

LV, it could be that rather than a "pure" apnea, you're more in the upper airway resistive syndrome (UARS) category like me.

In my study, I only had an AHI of 6 which would have placed me in a very mild apnea category. My RDI, on the other hand, was over 50 and considered severe. The issue is that when my airway collapsed (i.e. for an apnea event), my brain was waking up too quickly for it to score the drop in blood oxygen saturation associated with a "real" apnea event....still felt like crap in the morning from not sleeping, but not getting the AHI numbers that would traditionally explain it.

UARS is a form of obstructive sleep breathing, like apneas, but not all docs will diagnose UARS....they just lump it all into OSA and be done with it. An RDI of 18 with an AHI of 1.5, to me at least, suggests moderate UARS, which is real and just as much an issue as OSA. Sure, you don't have an 18 AHI...but for what an RDI of 18 does to your sleep, you may as well have...at its most simple level, the differences are the length of events and what's happening to your blood O2 levels.

Thanks for such a thorough explanation! What you are describing sounds exactly like what I'm going through. Now I feel better knowing more and about making the decision to purchase the CPAP.

[vsheline]

I have an AHI of 1.5 and an RDI of 18.5 and my doctor has diagnosed me with moderate OSA for which I am now on a CPAP. All the information that I've been reading focuses on the AHI and that if it's below 5, it's normal.

Do cpap machines keep track of RDIs? Is that something that will transmit to sleepyhead? (I've been reading the forum post on it.)

I guess, am I really suffering from moderate OSA if my AHI is normal. I'm not 100% happy with the doctor that I'm seeing and I'm worried that maybe he is pushing the CPAP therapy on me when it doesn't need to be.

RDI is a better criterion than AHI to use to diagnose obstructive sleep apnea. Here is an article from the American Association of Sleep Medicine which on page 267 uses RDI rather than AHI to define the ranges for severity of Obstructive Sleep Apnea. Mild OSA is RDI 5 to 15, Moderate OSA is RDI 15 to 30, Severe OSA is RDI 30 and above:
http://www.aasmnet.org/Resources/clinica...Adults.pdf

In Table 2 of this article from Mayo Clinic Proceedings Jun 2011, it is explained that people with UARS are now given a diagnosis of Obstructive Sleep Apnea:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3104914/

The RERA detection algorithm used by Philips Respironics is described in brief by robysue in the post linked below (in the section near the beginning labeled "Other flagged events"). Personally, I think the Philips Respironics RERA detection criteria would be likely to score (count) only a minority of the total number of RERA events which are occurring, and I think it is not as likely to be fooled into falsely counting a RERA as having occurred when actually one had not occurred, so I think the number of RERA events reported would tend to underestimate the true number of RERA events.
http://www.apneaboard.com/forums/Thread-...A#pid73576