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General Discussion on any topic relating to CPAP and/or Sleep Apnea.
monica4patience
 
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Sudden increase in AHI?

Postby monica4patience on Fri Jan 07, 2011 9:24 am

My AHI had averaged 1.5 for 11 days. Wednesday night it increased to 3.4 and last night was 4.1. I have done nothing differently the past two nights. What would cause the AHI to increase so much?

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robysue
 
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Re: Sudden increase in AHI?

Postby robysue on Fri Jan 07, 2011 10:08 am

monica4patience wrote:My AHI had averaged 1.5 for 11 days. Wednesday night it increased to 3.4 and last night was 4.1. I have done nothing differently the past two nights. What would cause the AHI to increase so much?


Are these changes in the 7 day AHI averages on the PR System One's on-board LCD?

Or are they changes in the overnight numbers as seen in Encore Viewer?

It makes a HUGE difference whether this is a ONE day jump in the 7 day AHI on the PR System One's on-board LCD or just the overnight number in Encore Viewer...

Because if your 7 day average suddenly jumped from 1.5 to 3.4 overnight, that requires a huge overnight increase in AHI on Wednesday night. (Smaller, steadier increases should have started increasing the AHI from 1.5 before Wednesday night). To see why, we can analyze a very simplified example. For our simplified example, let's suppose you sleep 8 hours every single night with the PR S1 running. And you've had and AHI of 1.5 for at least 11 days. So we'll make a rough and simplified estimate that your actual AHI for the seven nights prior to the Wednesday in question are:


    Previous Wednesday: AHI = 1.5 (so you had a total of 1.5 * 8 = 12 events that night)
    Thursday: AHI = 1.5 (so you had a total of 1.5 * 8 = 12 events that night)
    Friday: AHI = 1.5 (so you had a total of 1.5 * 8 = 12 events that night)
    Saturday: AHI = 1.5 (so you had a total of 1.5 * 8 = 12 events that night)
    Sunday: AHI = 1.5 (so you had a total of 1.5 * 8 = 12 events that night)
    Monday: AHI = 1.5 (so you had a total of 1.5 * 8 = 12 events that night)
    Tuesday: AHI = 1.5 (so you had a total of 1.5 * 8 = 12 events that night)
    Tuesday Morning 7 day AHI is computed as (84 events)/(56 therapy hours) = 1.5

Now for the Wednesday 7 day AHI, the previous Wednesday's events and therapy hours are dropped out of the calculations and replaced by the current Wedneday night's numbers. We'll continue to assume that you slept for 8 hours with the machine running just to simplify how the numbers in our example calculation work. And I'll let n be the number of events you had that Wednesday night. Now what we know is this:

The number of events in the AHI calculation is 6*12 + n because you had 12 events on each the six nights Thursday through Tuesday and n events on Wednesday night.

The number of therapy hours is 7*8 = 56 because we're assuming that you slept 8 hours each night in order to simplify things.

The seven night AHI average is 3.4 as stated in your post.

So now we get the following equation and we have to solve for n:

(6*12 + n)/56 = 3.4

72 + n = 190.4 (multiply both sides by 56)

n = 118.4 (subtract 72 from both sides)

So n is most likely 118 or 119 because you can't have 4/10 of an apnea or a hypopnea. (Remember that n is the actual number of apneas and hypopneas you had on Wednesday night.) And that means that your Wednesday night AHI is a whopping huge 118/8 = 14.75 or so.

Note: This is why I personally think the 7 day average AHI numbers on the System One figures are so useless. I really wish that the System One machines would really provide the overnight numbers on board the way the ResMed S9's do. Just my two cents.

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monica4patience
 
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Re: Sudden increase in AHI?

Postby monica4patience on Fri Jan 07, 2011 11:43 am

Sorry I didn't make myself clearer! The 11 day average was just my computation of the previous 11 days. All the AHI data taken directly from Encore Viewer for each day, not an average. I went back 11 days only because all other factors were fairly similar: Remzz's mask liner, no hose cover.

But since increasing my pressure to 8 on 12/15 my AHI has averaged 1.4 with a low of.8 to a high of 2.3. I didn't include those numbers because I was still playing with the mask, adjusting for leaks, using/not using a hose cover, etc.

My health is the same: no congestion, no coughing. I can't see where it would start going up again.

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robysue
 
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Re: Sudden increase in AHI?

Postby robysue on Fri Jan 07, 2011 12:05 pm

May just be a random pair of bad nights. That happens occasionally.

I'd see if it goes back to normal in the next couple of days.

I've noticed in my own data that when I do have a bad day for no apparent reason, it's usually a string of 2 or 3 bad ones (sometimes with a couple of normal days in between the bad ones) and then all is back to normal.

Or the the 2 or 3 bad days in a row are the earliest symptoms I'm getting sick---even before the congestion sets in.

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monica4patience
 
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Re: Sudden increase in AHI?

Postby monica4patience on Fri Jan 07, 2011 2:32 pm

"Or the the 2 or 3 bad days in a row are the earliest symptoms I'm getting sick---even before the congestion sets in."

Yikes, I hope that's not the case!!! I feel like I'm finally getting back into a routine of cooking and cleaning after the kids are back to school. I really, really do not want to have a set-back by getting sick.

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jbn3boys
 
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Re: Sudden increase in AHI?

Postby jbn3boys on Fri Jan 07, 2011 2:43 pm

How long have you been using your mask? I know over time they can start to wear down, and not be as effective. Nasal pillows, for example, are usually replaced every 2-6 weeks. With your nasal mask, it should be considerably long than that, but at some point most masks need to be replaced (or at least the seal needs to be replaced) I think the Medicare coverage is for a new mask every 3 months (and most insurance companies follow Medicare guidelines).

Another thought, since you said you feel like you are just getting back into cooking and cleaning, is that you are just plain old tired! Sometimes, if we are over-tired, I think numbers can be effected.

Or, what about mouth breathing? Have you possibly started mouth breathing and losing your therapy air that way?

Just trying to think of different things that could influence your numbers....

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Additional Comments: titration 11
Sleep study (Aug 2010): AHI 16 (On mask AHI 0.2) <-- Now, if I could just attain that "0.2" again!
aPAP for 4 months, Switched to BiPap, 2nd sleep study Feb 2011 Possible PLMD
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Jersey Girl
 
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Re: Sudden increase in AHI?

Postby Jersey Girl on Fri Jan 07, 2011 4:17 pm

I also experienced a sudden increase in AHI - 3 nights in a row! I have been ill with a GI tract infection and so, I raised my pressure by .2 the first night, checked my numbers and then raised it another .2. Now, at 8.4 my AHI is back to 1.9. I am checking each day to see how the numbers are going. I only increased the pressure this time around, because my numbers were running 4.7 to 5.5 with 0.00 to 0.04 leak rate, which meant that I had a really good fit with my mask, but due to illness needed a slight increase of pressure to keep the AHI down.

I have also noted that I tend to have slight higher numbers the first night I change to a different mask.

For me, at least 2 things affect my AHI: Illness and mask change.

Let us know how things continue to go for you.

Best regards,

Jersey Girl

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monica4patience
 
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Re: Sudden increase in AHI?

Postby monica4patience on Sat Jan 08, 2011 11:22 am

jbn3boys wrote:How long have you been using your mask?

Another thought, since you said you feel like you are just getting back into cooking and cleaning, is that you are just plain old tired! Sometimes, if we are over-tired, I think numbers can be effected.

Or, what about mouth breathing? Have you possibly started mouth breathing and losing your therapy air that way?

....


This is only Week #5 on the CPAP and first mask.

How do I know if I'm mouth breathing? Wouldn't that affect the leak rate? During the sleep study they didn't use a chin strap and didn't mention that I may be mouth breathing. DME gave me a chin strap, but I really didn't think I needed it. Maybe I do.

Well....last night the AHI dropped down to 1.8 with no other changes on my part. If it goes up again I may try to make some changes. I know that since using the Remzz's there's not as good a seal....I can easily talk with the mask on. Whereas, when I was using silicone ear plugs along the bridge of my nose, I got a really good seal (when I was sitting up!) and had a really hard time trying to talk with the mask on.....you know the kids or DH always need to talk to me as soon as I'm all settled in bed (or in the bathroom, LOL, they could go for hours without talking to me, but let me get in bed and they just have to ask me something or tell me some great story!!! Anyway, that great seal would disappear once I laid on my side and would blow into my eye. I don't get that effect with the Remzz's.

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chunkyfrog
 
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Re: Sudden increase in AHI?

Postby chunkyfrog on Sat Jan 08, 2011 12:13 pm

I just had the same thing happen; I had run out of Aciphex and am experiencing a dull stomach pain most of the time.
I'm expecting my refill in Monday's mail--then my numbers should come back down. (crossing fingers)
You might check for other symptoms--it all works together.

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jbn3boys
 
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Re: Sudden increase in AHI?

Postby jbn3boys on Sat Jan 08, 2011 2:27 pm

monica4patience wrote:How do I know if I'm mouth breathing? Wouldn't that affect the leak rate? During the sleep study they didn't use a chin strap and didn't mention that I may be mouth breathing. DME gave me a chin strap, but I really didn't think I needed it. Maybe I do.

I don't have any experience with mouth breathing, so I'm not the best person to ask. If you wake up with a dry mouth, that's a good sign of mouth breathing, but I'm sure there are others. I'd suggest doing a search of the forums for mouth breathing. sorry I can't be more help.

Glad you had lower numbers last night! Maybe it was just a couple rough nights.

_________________
Mask: Swift™ FX For Her Nasal Pillow CPAP Mask with Headgear
Humidifier: PR System One Heated Humidifier
Additional Comments: titration 11
Sleep study (Aug 2010): AHI 16 (On mask AHI 0.2) <-- Now, if I could just attain that "0.2" again!
aPAP for 4 months, Switched to BiPap, 2nd sleep study Feb 2011 Possible PLMD
to quote Madalot..."I'm an enigma"


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