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I have to ask.. Why the concern over low AHI's
#1
Question 
I am an unwilling CPAP participant that has somehow missed the first rung of the ladder as I find myself standing on the second rung. (Meaning, a run-down sleep condition brought me here and it becomes necessary to understand what I might expect to see improve)  I will be attending my second sleep study tomorrow and awaiting the Doctors prescription, not sure what it will be but it probably will be a sophisticated Bipap as LVEF < 45% apparently rules out ASV.  So as of this moment I have no CPAP of any kind in use.  That said;
 
Speaking in generalities I see here people with AHI’s from maybe the 80’s to low single digits.  It is obvious ‘why’ the high-rollers desire significant reductions, but ‘why’ are the low digits (next to Zero) concerned with trying to actually get to Zero? Does ZERO AHI really mean that much?  Or is it like a Bonneville speed car, just the challenge of competing; Or is there a definable purpose to the quest?
 
Why do people high and low both have issues if the purpose of CPAP therapy is to correct such issues? I am at ends to understand if there is a reasonable expectation to once again expect a restful night’s sleep.  If so, why are people with low AHI’s still purportedly having problems?
 
Would appreciate a definitive explanation, ..I am trying to better understand.
Thanks.
Counting SHEEP can be hazardous!
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#2
(10-12-2017, 12:18 PM)zzzZorro Wrote: Why do people high and low both have issues if the purpose of CPAP therapy is to correct such issues? I am at ends to understand if there is a reasonable expectation to once again expect a restful night’s sleep.  If so, why are people with low AHI’s still purportedly having problems?
 
Would appreciate a definitive explanation, ..I am trying to better understand.
Thanks.

While it is relatively obvious why individuals are worried about higher AHI's and continually improving their numbers, it is also true that you treat the patient and not the machine. That is, you can still feel crappy with low numbers -- especially if you are running low oxygenation numbers at night.

When I started  in 2008, I was told, don't worry about anything under AHI = 5.0 as that is "normal" and to be expected. But the AHI number is not the whole story as you can have other comorbidities (medical conditions) that affect your sleep and are not reflected in the machine-calculated AHI. There are a number of subclinical events which are present that do not show up in the AHI but can have a cumulative effect over time.

Example: My AHI for yesterday is 0.79 (2 Obstructive Events; 1 Clear Airway Central Event; 4 Hypopneas, 2 RERA Events; 183 Sp02 drops (oximetry); and 30 User Flag events -- 50% FLOW RESTRICTIONS FOR 8-SECONDS -- which are not in the AHI but can have a cumulative effect.)

It is not that I am chasing a zero AHI as some form of badge of honor, but trying to reduce all potentially cumulative adverse events (including those designated by the "user flags") to zero.

Hope this helps. Have a great sleep tonight for a better tomorrow.
"The object in life is not to be on the side of the majority, but to escape finding oneself in the ranks of the insane." -- Marcus Aurelius
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#3
Good question. 

In my case I had excellent AHI numbers about 6 months into treatment, but was battling to sleep with the mask on for more than 4 or 5 hours. I felt as if I was struggling against the machine all night, getting a work out rather than sleeping. I was on the path to becoming one of those patients who eventually stop using CPAP... I was concerned because I knew how important this is for my health. 

So despite the low AHI I started really checking out my data in SH. 

Turns out that my great sub 1 AHI was  not the whole picture, I still had quite awful lingering flow limitations and they needed to be eliminated through a combination of higher pressure and EPR 3 which for me made breathing comfortable, even pleasant actually. 

Now I'm sleeping all night with the mask on, good, deep sleep and feeling great during the day. 

AHI might even be a tad higher  due to a few centrals creeping in thanks to EPR ... but worth it for the great sleep. Rarely over 2 anyway. 

It  has to do with analyzing our data to get the best possible results for optimal treatment, sleep and long term health.
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#4
For myself, I can notice a large difference the next day between a night with AHI < 1 and a night with AHI > 2.  It is like being hungover.  That is why I try to get my number low.  It is 100% based on how I, personally, feel the next day.
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#5
(10-12-2017, 12:18 PM)zzzZorro Wrote: I am an unwilling CPAP participant that has somehow missed the first rung of the ladder as I find myself standing on the second rung. (Meaning, a run-down sleep condition brought me here and it becomes necessary to understand what I might expect to see improve)  I will be attending my second sleep study tomorrow and awaiting the Doctors prescription, not sure what it will be but it probably will be a sophisticated Bipap as LVEF < 45% apparently rules out ASV.  So as of this moment I have no CPAP of any kind in use.  That said;
 
Speaking in generalities I see here people with AHI’s from maybe the 80’s to low single digits.  It is obvious ‘why’ the high-rollers desire significant reductions, but ‘why’ are the low digits (next to Zero) concerned with trying to actually get to Zero? Does ZERO AHI really mean that much?  Or is it like a Bonneville speed car, just the challenge of competing; Or is there a definable purpose to the quest?
 
Why do people high and low both have issues if the purpose of CPAP therapy is to correct such issues? I am at ends to understand if there is a reasonable expectation to once again expect a restful night’s sleep.  If so, why are people with low AHI’s still purportedly having problems?
 
Would appreciate a definitive explanation, ..I am trying to better understand.
Thanks.

zzzZorro, you have a bigger challenge ahead of you, not only in sleep apnea, but other health issues.  Everyone comes here with their own personal expectations for CPAP.  You may have noticed that once they start therapy, EVERY problem is related to CPAP.  We do our best to get members comfortable with the therapy, and as low as possible in terms of AHI.  Those results vary from consistently less than 1 event per hour to somewhere under 10 events.  Above that threshold, we generally conclude a different therapy path is in order.   I would suggest that a few years ago you would have been prescribed ASV regardless of LVEF, and you would have greatly benefitted.  Nothing has changed except for the Resmed study that found a statistically higher rate of cardiac death in patients treated with ASV and that had LVEF<45%.   That finding is still under review and study.

Everyone wants to do as well as possible, and the data can cause some obsession with the numbers vs results.  Personally, I only check the data once a month, and rarely think about making any changes.  So all of us are different, and as the years go on, we tend to be less concerned with the numbers, and respond more to our sense of well-being.  If you read the forum, that is not the message, since many of the more prolific posters asking advise are in their first month or two of therapy.  Those of us that have done this a while have a different perspective.
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#6
My perspective as a new poster with a low AHI under treatment who fits your description (others' perspectives and reasons may vary):
  • I'm not concerned with getting to zero - I expect there will always be some number of events and attempting to eliminate all of them is probably not possible due to the tradeoffs involved, not to mention having different sleep conditions from night to night, a temporarily poor mask fit, imbibing or ingesting various sleep-affecting substances, and so on...
  • AHI and how you feel don't necessarily have a linear relationship; plus AHI is a composite of multiple different types of events, which are going to have a different effect on you.
  • Someone might have a low AHI, but may still not be getting the quantity of sleep they need, or have more interruptions/awakenings/times knocked out of restorative sleep at night than is desirable.

Now that I'm using SleepyHead, I'm also trying to track how I feel qualitatively each night. I am doing much, much better than before my diagnosis, but if there are further easy improvements I can make to my therapy, I want to make them, and then get into a sort of "steady state" where I don't need to worry about it unless I notice things start to backslide.
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#7
I agree with those who point out that AHI and "restedness" the next day are very imperfectly correlated. There have been more than a few days when I've had AHI<1 and felt lousy the next day, as well as days with AHI>3 and I felt great.

My sleep study showed a significant number of spontaneous arousals and PLMs. These definitely affect sleep quality and are not closely related to breathing issues, although in my case the SAs did cluster strongly around a particular EPAPmin setting for some reason. In any event, I've had some zero nights too and they're nothing special.
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#8
I don't think I need to add much to this as most has been said, the first explanation is as good as it gets.

I had a CPAP with a pressure of 18 and now have a APAP and it gets up to almost 12.

I did have on CPAP
Ahi of 2 sometimes 3 at worst.
However I felt as if I had a good sleep and felt as bright as a button in the morning.

Now with the APAP:
Ahi 0.07
I don't feel quite so bright in the mornings.
May be not so well ventilated, I don't know as I have not got round to setting up Sleepyhead yet.
How can I have 0,07 of an AHI?

So low numbers are not always what is required.

What my partner noticed is that I used to breathe deeply with the CPAP machine and with the APAP I take a lot shallower breaths, but more of them.
So it is not quite as simple as low numbers, though you would think it was listening to sleep doctors.
I am told people have apneas during the night naturally, it is just when it increases it becomes a problem.
Some people can have a few every night, but with a sleep apnea patient, they last longer and there are many more of them, this is what causes up a problem.
There may be people out there that have CPAP/APAP machines that would be better with a more complicated machine.
Depends how good the sleep doctor was or how much importance the doctor placed on events during the study.
When done at home there is even less chance of something being picked up.
Don't worry about low numbers, if you get somewhere below 5, I wouldn't worry to much, as long as the tiredness and fatigue has gone.
It can sometimes be worth getting an oximeter, my next purchase, just to see if the oxygen levels are still fine.
But that is just my choice. 

Just checked the readings on my machine:
145.3 hrs
Ahi 0.4
Central 0.1
Total 0.1
Pressure 11.5
Leak 37ltr per minute, this was due to me getting the hose caught in my arms and pulling of the mask a few times the first two nights Rolleyes 
Anyway, it is improved readings on what it used to be.  The only thing is I feel tired a bit earlier at night, I have to go to bed at 12am instead of 2am Rolleyes  Not quite as sharp in the mornings, but then I have other problems that might be influencing things.
However I love my new machine, they are NOT getting it back!!!   like 
So as you can see, low numbers are not always what you need, I think some get obsessed with it.
A lot of people are carrying extra weight as well and have other medical problems as well, so a low number might still leave them feeling like crap in the morning, even though they may have got their Ahi down.

Clear as mud is it?   Rolleyes
Being blown in the CPAP/APAP wind in   Undiscovered Bonnie Scotland
CPAP/APAP is a breath of fresh air!
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#9
Thanks  To all of you. It appears this 'numbers' thing is a bit of a conundrum to just not me.  Appreciate the help with getting a grip on it.

Sleeprider:  Your reply, " I would suggest that a few years ago you would have been prescribed ASV regardless of LVEF, and you would have greatly benefitted.  Nothing has changed except for the Resmed study that found a statistically higher rate of cardiac death in patients treated with ASV and that had LVEF<45%.   That finding is still under review and study" is something I have been concerned over.  It appears an ASV is the real ticket to what is needed to get a handle my apnea issue, but it seems all the Doctors are going to align behind a study that still has the 'jury out' for fear of litigation..
I suspect tonight at the sleep study they are geared-up for studying the BIPAP ST mentioned earlier and will not even be giving an ASV a test ride.
Counting SHEEP can be hazardous!
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#10
Interesting article September, 2015.  Notice where in the last nine paragraphs on CSA and CHF (chronic heart failure) it suggests, "One possible explanation for this is that central sleep apnoea may actually be a compensatory mechanism in some heart failure patients".
Counting SHEEP can be hazardous!
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