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[CPAP] AHI = 1.0 – too good to be true?
#1
Question 
Hi,

I am a bit suspicious about unusually low AHI that my brand new ResMed S9 reports. Hope somebody can provide some advice.

I have been diagnosed in 2006 with OSA with AHI =10. I was titrated at the lab for CPAP pressure 9.

Since then I’ve been using APAP/CPAP machines every single night. I had 3 machines:
1. Respironics REMstar Auto 2006 to 2009
2. ResMed S8 AutoVantage 2009 to June 2013
3. I’ve just got a few days ago ResMed S9 Autoset

On #1 and #2 machines I really could not use APAP mode over long time. I was setting APAP pressure to min 6 and max 11.5. I was frequently awaken up by high pressure close to max blowing into my nose. So for the most of the 7 years I was using the machines in CPAP mode with pressure set to 9. And all these years my AHI index was around 5.


With the new ResMed S9 in auto mode, the machine shows AHI=1 or less. Can it really be that machine provides that level of improvement, or something is different in how S9 calculates and reports AHI? I.e. do I really get a better treatment or this is a gimmick from ResMed.
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#2
No its not a gimmick, for an apnea to get scored have to last 10 seconds or more, obstructions less than 10 seconds are not scored as an apnea. To get technical you need to look at waveform and flow limitations graphs

Prolong leaks above 24 L/min can affect the accuracy of data reporting
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#3
It is very possible indeed!

The only time to be concerned that your machine is possessed by aliens is if the S9 shows zero AHI for more than a day. It is some kind of quirk (aliens!). To fix it, just unplug it for about 30 seconds and plug back in.

Your machine is data capable. All you need is a card reader. You can get a real cheap one for just a few bucks if your computer does not have one. Both ResScan and SleepyHead work with your machine. Try using both of them for a few weeks to decide which one you like.

Looking at the data would let you know how often you bump up against your upper limit, if you do at all.
PaulaO2
Apnea Board Moderator
www.ApneaBoard.com


Breathe deeply and count to zen.

INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.




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#4
Hi Mark Opti!

Welcome

You are in the right place.

Since I got everything with my sleep tuned up I am doing about 0.4 to 1.5 with an occasional 0.0!

This is good for you, because it means your machine is kicking some OA butt!
You will need to be always vigilent though so get the SleepyHead going and you'll be monitoring
your own therapy so you can take corrective action when the time comes.

Good Luck, Cheers & Sleep-well






"With ordinary talent and extraordinary perseverance, all things are attainable." - Thomas Foxwell Buxton

Cool
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#5
I THINK:

1) The S9 AutoSet does a better job of finding the right pressure and treatment in general than the S8.

2) The S9 scores fewer apneas vs. the S8 for many people due to changes in the detection algorithms. There are some things that fall in the "gray area." I don't think this is "marketing," and that the newer algorithm is more in line with what the medical professionals think in terms of scoring apneas.

Even if everything is "right," there's still some "judgment" in apnea diagnosis and treatment. Sometimes, one thing works better than another, and you have no real explanation why.

If your AutoSet ever starts showing 0 AHI night after night, unplug the power for a few minutes. A number of people have reported their machines getting "confused" and needing a reboot. Unplug the power, don't just turn it off. It doesn't seem to affect treatment, just data recording. Also, it's a "stuck on 0.0" problem, not a "record low values" problem.
Get the free SleepyHead software here.
Useful links.
Click here for information on the main alternative to CPAP.
If it's midnight and a DME tells you it's dark outside, go and check it yourself.
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#6
Another point is to not be automatically afraid of what seem to be high AHI values. From personal experience, if I have my CPAP on but am futzing with my pillows or something, I will often end up periodically (consciously) holding my breath for long enough to register as an obstructive apnea. Look at your collected data. If all (most) of the apnea events are right at the start or end of a session, they will contribute to the overall AHI for the session, but aren't really "real". Look at what is happening while you are asleep to see if there really is a problem.

This is why most people tell you to run away from "brick" (non data-logging) machines. Just the summary can be misleading.
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#7
S9 AutoSet nuke apnea events before occurring as it respond to snoring and flow limitation which are precursors to apnea events. Also differentiate between obstructive and central apnea through FOT, take no action if open airways is detected but deal with it if closed airways is detected. For this reason the S9 enhanced algorithm is more efficient than its predecessors

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#8
Thumbsup 
Thanks a lot to all for the input!

As I said, my main concern was that for 7 years on 3 other machines (REMstar Auto and two S8 Vantage) I was hovering around AHI 5. So I was looking for a possible explanation about why that much difference with S9.

I think, like Archangel pointed, S9 does both:
1. Does better job with different algorithm
2. Interprets data differently.


I did check SleepyHead reports – everything looks good. I do feel that S9 has better Auto mode. Other machines were going to Max pressure often and that woke me up. So I used most of the time CPAP mode.

S9 seems has very nice Auto algorithm and applying Max pressure more intelligently (not as often).
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#9
(06-16-2013, 09:14 PM)Mark Opti Wrote: I do feel that S9 has better Auto mode. Other machines were going to Max pressure often and that woke me up. So I used most of the time CPAP mode.

S9 seems has very nice Auto algorithm and applying Max pressure more intelligently (not as often).

This used to be common in older APAP machines. It's why even today, many sleep doctors are prejudiced against APAPs, thinking that the pressure can "run away" and go to the max too soon, as you described.

But with today's newer machines, this just doesn't happen much any more, making APAPs the machine of choice for many OSA patients.



SuperSleeper
Apnea Board Administrator
www.ApneaBoard.com


INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.



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#10
Congrats for the Low AHI

We all aim for below 5

But the Main thing is How are you Feeling if you Feel great with a AHI of Say 3
Does worrying about getting it any lower really help
If its not broke don't Fix it
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