AHI Mystery

General Discussion on any topic relating to CPAP and/or Sleep Apnea.
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Darth Lady
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AHI Mystery

Post by Darth Lady » Tue Mar 31, 2015 7:54 pm

So I've been on therapy for about 2 full months now, and since I'm still feeling pretty dragged out and sleepy during the day, my sleep doc sent me home with an Itamar WatchPat to see how I was doing.

According to my machine, my AHI has always been below 1. Super-duper. According to the WatchPAT, which uses some combination of oximetry and arterial tonometry that is supposed to be pretty accurate, my AHI was over 12 and my RDI was about 22 .

What on earth is up with that? We've got the DME coming over in a couple of days to make sure darling Dartha is working properly, for what that's worth . If they determine that it's not Dartha's fault, it's back to the lab for a re-titration for me. Which is odd, because according to Dartha, I don't have a problem, but according to WatchPat, and how I'm feeling, I do....

The only theory I have is that I'm just not breathing enough at night, so that I desaturate, and WatchPAT picks up that, with the body's subsequent efforts to right things, and labels that as an event. How, with my machine, would I fix that?

The only notable change over the weeks has been that the PS, the pressure support (which is set to min 0, max 20 or thereabouts) started out for the first few days as at least 10 at all times. After three nights, it abruptly went down to a range of 0 to 10. Not sure why that happened. Right after it dropped, I had a severe asthma attack that put me in the ER. That has all cleared up now, but Dartha has never returned to those high PS levels. Does that have anything to do with anything? I know these machines are not meant to be ventilators, but perhaps more pressure support would generate more tidal volume, generating higher SpO2 values and a happier brain?

I'm kind of eager to avoid in-lab Sleep Study No. 4 if I possibly can, so any thoughts anyone has would be appreciated.

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Julie
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Re: AHI Mystery

Post by Julie » Tue Mar 31, 2015 9:12 pm

I don't quite understand the low pressure of 0... most machines bottom out at 4, 1-2 at 3, and most people cannot breathe properly at either. Have you tried a higher starting low setting, e.g. 6 or 7 to see how effective it might be? Even with good AHI #'s, if you don't feel good you should try tweaking the basics (one at a time of course).

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Pugsy
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Re: AHI Mystery

Post by Pugsy » Tue Mar 31, 2015 9:41 pm

Julie wrote:I don't quite understand the low pressure of 0...
She's talking about PS or pressure support which is of course the difference between inhale and exhale and with the ASV machines there is a wide range available and that does include 0...available on the PR S1 960 and the AutoSV ResMed machines.

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Uncle Flapp
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Re: AHI Mystery

Post by Uncle Flapp » Tue Mar 31, 2015 10:20 pm

I noticed my PRS1 960 ASV misses flagging events.

Here is what appears to be a CA episode last night that woke me pretty abruptly. No flags by the machine.
Image

Not sure if this helps but it reiterates that the machine ain't perfect at flagging them all.

- Flappy

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Darth Lady
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Re: AHI Mystery

Post by Darth Lady » Wed Apr 01, 2015 6:54 am

Machine-triggered or timed breaths seem (seem) to work pretty well for me in those situations - they exert enough pressure to get air into my lungs. In fact, the first three days I used the machine, most of the breaths were machine-triggered. Then that stopped, and now they are usually 20-30 per night. Honestly, I kind of missed them. I think the machine is better at breathing than I am .

I've also noticed that there is something about clear airway events that seems to cause a lot of them not to get flagged. But I've looked at that wave form over entire nights, and I don't seem to be having many of them - a timed breath seems to start me breathing again most of the time. Just not, apparently, deeply enough.

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winnie
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Re: AHI Mystery

Post by winnie » Wed Apr 01, 2015 10:04 am

Uncle Flapp wrote:I noticed my PRS1 960 ASV misses flagging events.

Here is what appears to be a CA episode last night that woke me pretty abruptly. No flags by the machine.
Image

Not sure if this helps but it reiterates that the machine ain't perfect at flagging them all.

- Flappy

I have similar types of things. How do you know it is a CA? Sometimes my Resmed Autoset 9 flags them as hypopneas, sometimes doesnt flag them. I seem to have dozens of these every night but they dont wake me. Here is a typical one:

Imagesleepyhead april 1 by pug_gramma, on Flickr

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Uncle Flapp
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Re: AHI Mystery

Post by Uncle Flapp » Wed Apr 01, 2015 1:44 pm

winnie wrote:How do you know it is a CA?
I don't know for certain. It could be a physical obstruction but with being diagnosed with CompSA, I assumed the former.

- Flappy

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SGearhart
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Re: AHI Mystery

Post by SGearhart » Wed Apr 01, 2015 2:53 pm

Darth,
The only thing I found about the WatchPAT was that it worked better on bus drivers over the age of 45. I'm not going to ask your age, but do you drive buses?

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Darth Lady
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Re: AHI Mystery

Post by Darth Lady » Wed Apr 01, 2015 5:26 pm

Darth Lady will confess to being on the heavenward side of 45, but she would never drive a bus. Darth Lady only drives a TIE fighter.

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Darth Lady
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Re: AHI Mystery-Apres DME Tech

Post by Darth Lady » Thu Apr 02, 2015 7:45 pm

So the DME's tech came today and told us that the machine is fine, by the highly scientific method of sticking his finger in the air output - yup, it's blowing!

Like we didn't know that.

So here I sit, with my little mystery - why I would be desatting and racking up an RDI of 22 and AHI of 12 according to the WatchPAT study, when according to dear Dartha, I'm not having obstructive (or clear-airway for that matter) events?

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Uncle Flapp
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Re: AHI Mystery

Post by Uncle Flapp » Fri Apr 03, 2015 9:16 am

Have you thought about purchasing a pulse oxymeter and importing the data into Sleepyhead? You should be able to compare any desats to your flow rate.
I bought this one on Amazon. I believe Pale Rider found it cheaper on AliExpress.

- Flappy

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Darth Lady
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Re: AHI Mystery

Post by Darth Lady » Fri Apr 03, 2015 11:07 am

I have had my eye on that oximeter for a while. Interesting to note that they used to claim that it did NOT work with SleepyHead, and now they only say they won't GUARANTEE it will work with SleepyHead . I may yet invest in it.

My frustration is that even if I got that, and correlated all the data, I just don't have enough flow limitations (either that the machine records, or that my eyes can see) to account for the number of events per hour the WatchPAT study claimed I was having. So I'm no closer to knowing what might cause the desats. So it looks like it's back to the lab for me....

I mean, I can think of a few things that could cause that, but they are all pretty nasty.

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Re: AHI Mystery

Post by palerider » Fri Apr 03, 2015 12:42 pm

Darth Lady wrote:I have had my eye on that oximeter for a while. Interesting to note that they used to claim that it did NOT work with SleepyHead, and now they only say they won't GUARANTEE it will work with SleepyHead .
no rolling needed, it didn't work with the OLDER versions of sleepyhead, it works with the 098-1 version, because Mark changed sleepyhead.

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Darth Lady
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Re: AHI Mystery

Post by Darth Lady » Fri Apr 03, 2015 1:32 pm

Good to know - thanks

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