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AHI and RDI
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graeme Offline

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Post: #1
AHI and RDI
It will be several months before I see my Sleep Doctor to get an answer to this subject that has been bugging me. My questions are...

What is the difference between RDI (Repiratory Distress Index) and AHI (Apnea Hypopnea Index) ?

Why are both used?

BOTH use the same criteria for determining severity, ie. 5-15 Mild, 15-30 Moderate and greater than 30 Severe.
HuhHuhsign
09-17-2014 04:17 AM
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zonk Offline

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Post: #2
RE: AHI and RDI
AHI http://www.apneaboard.com/wiki/index.php?title=AHI

RDI http://www.apneaboard.com/wiki/index.php?title=RDI
09-17-2014 04:45 AM
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PaulaO2 Offline
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Post: #3
RE: AHI and RDI
In other words, AHI is:

obstructive + central + hypopnea / # of hours slept

RDI is

respiratory-effort related arousals (RERA) + AHI / # of hours slept

RERA is where you aren't narrowed enough to have a true hypopnea but it is enough that it pulls you out of sleep or disturbs your sleep. RERA, I suppose, could only really be measured during a sleep study. A CPAP machine might give it a good guess based on breathing pattern but it is going on assumptions you were asleep to begin with.

RDI is useful in determining initial diagnosis and, I suppose, to determine if treatment is working if followed up by another sleep study.

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09-17-2014 04:49 PM
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Terry Offline

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Post: #4
RE: AHI and RDI
(09-17-2014 04:17 AM)graeme Wrote:  It will be several months before I see my Sleep Doctor to get an answer to this subject that has been bugging me. My questions are...

What is the difference between RDI (Repiratory Distress Index) and AHI (Apnea Hypopnea Index) ?

Why are both used?

BOTH use the same criteria for determining severity, ie. 5-15 Mild, 15-30 Moderate and greater than 30 Severe.

FWIW, RDI is a much better indicator of how I feel when I wake up. The RDI is a big component of me feeling awful.

Terry
09-17-2014 06:56 PM
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zonk Offline

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Post: #5
RE: AHI and RDI
From http://www.apneaboard.com/forums/Thread-...or-Useless

Probably the best indicator of SDB, however, is simply the response to continuous positive airway pressure (CPAP) treatment. "It really is a no-brainer," Dr. Sullivan remarked, pointing out that CPAP administration is especially easy with the newer devices that automatically set the appropriate amount of positive pressure.
09-17-2014 11:19 PM
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PsychoMike Offline

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Post: #6
RE: AHI and RDI
(09-17-2014 04:49 PM)PaulaO2 Wrote:  RDI is useful in determining initial diagnosis and, I suppose, to determine if treatment is working if followed up by another sleep study.

Yup, Paula, it's useful for figuring out if it something like UARS vs. "normal" sleep apnea. Smile

Graeme, AHI is a great measure of actual apnea events that you're experiencing, while RDI is more an overall quality of sleep measure. They use both as if you have a high RDI, but low AHI, you may have something like Upper Airway Resistive Syndrome (UARS) which is like mini-apneas...but your body is reacting too fast to let them progress to full on apneas (with the corresponding reduction in blood oxygenation)...a high RDI due to UARS still keeps you from good sleep, though.

In my case, my RDI was 50+ while my AHI was only 6 during my first sleep study...I was pinned as a solid UARS patient and put on CPAP to deal with it.

If you are a UARS patient, you'll likely want to get your machine recorded AHI as low as possible. In my case (YMMV) there was an approximate 10:1 relation between RDI and AHI events, so my DME's "anything less than AHI=5" approach wasn't ideal...my initial 0.5 machine scored AHI probably meant an RDI of 5, which is an improvement, but still not great. My recent numbers are more like AHI = 0.05, so an RDI~0.5...I'm definitely sleeping a heck of a lot better than I have in the past.
09-18-2014 11:48 AM
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