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Advise on (to me) strange AHI pattern
#1
Can anybody please tell me if I'm reading the attached sample night correctly in thinking that the leak is quite low and unlikely to be responsible for the spike in AHI up to 40+ AHI over the course of an hour.

I understand you're not doctors but if anybody can tell me if I'm reading that aspect correctly or suggest anythings I should be investigating I'd really appreciate it. Fairly tired.

Weirdly, my nights tend to be like that one, with AHIs of <8 for an hour or two, followed by massive AHIs for an hour, without, as far as I can tell, leak being excessive.

The only thing I can think of is that it could be positional and that maybe I change position and in one I have an AHI of 7 or 8, and in the other I have an AHI of 30 or 40+.

APAP is set to 10.5-20 currently with a prescription of 11, but the APAP raising pressure doesn't seem to do much to stop the apneas.
This sample night had a larger than typical CA component, but it's typically about 3.0 CA (as guessed by the APAP).

I've been on CPAP for 2 years and APAP now for 25 days, with an average AHI of around 8.5 on the APAP and no CPAP AHI details other than being very comparably tired.


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#2
quozl, I am not very adept at reading graphs. When I tried AUTO I found the pressure kept going up and my AHI did too. I did better on a CPAP machine at a steady pressure. I also have been unable after 4+ years to ever get my AHI under five. In March I switched to ASV and my 30 day average AHI is 13.8 (my six month average before ASV was 28). Sometimes your leak does run slightly high. It's not unusual to have a cluster of events when going to sleep and during REM sleep. I assume you're in touch with your doctor and he put you on AUTO. I would give it two months and then see him with your results. After two years I wonder if you're tired because you're not getting good quality sleep. If your sleep is fragmented, or you have restless leg syndrome, or chronic pain you are probably not getting good sleep. Positional apnea certainly can be a factor. Wish I could be of more help. Also if you haven't had a physical I would explore other reasons for fatigue with your primary physcian. Good luck.
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#3
Heh, I told you I was tired - I didn't include the leak graph in the image I uploaded Smile

Here it is:

And @Zimlich, thank you for the suggestions. I did get a pretty comprehensive medical check-up when I got prescribed for the CPAP 2 years ago. Blood work, ECG and some other random stuff I can't recall. I see the doctor once a year and not scheduled to again until January - last time I saw them they offered me strong stimulants as I was still so tired. I've only found out that my AHI is still somewhat high because I stumped up for the APAP myself. The stimulants had some very rare but seriously scary potential side-effects and I figured they'd only at best mask the underlying issue.

[edit]And edit to attach the image. Again, I told you I was tired Smile) [/edit]

[attachment]
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#4
I suggest see your sleep doc. CPAP doesn't treat CA
Were there any CA in your sleep study
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#5
It looks like something real to me.

Zoom in and look at the airflow waveforms of some of the apneas you're having. Are they long, close together, full or partial airflow restrictions, etc.?

Is there any chance you're awake during the bad period?

By the way, everywhere but SleepyHead, "AHI" means average apneas for a whole night's sleep, not just over a one hour period.
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
quozl, my reading of your data agrees with what you see there. It does not appear that your AHI numbers are being compromised by a too high leak rate. However, like Zonk and archangle indicated, that CA seems to be calling for attention. It's just as high as the AHI number in the data you attached. Even if it's more like a 3 most nights, that still appears to be large enough to warrant some attention when you next see the doc. One other thought to share. If your AHI averages around 8 over time, it's possible that you're getting the best therapy you can. I offer that in light of my sleep doc telling me early on that although <5 AHI is the goal, I may not be able to reach that. He told me this along with the report that my apnea has proven challenging to control. It's possible that your apnea may also be difficult to get under that "magic" number of 5.
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#7
Thanks for the replies, it's really appreciated.

@Zonk - no mention of CA in my sleep study but I only got about a literal 30 minutes sleep during the hospital study (too uncomfortable) and they had to titrate me at home with what I assume was an APAP machine. So it probably didn't even measure CAs and considering the grouped pattern of my CAs if you were to look at a random 30 minutes of my sleep during the night you'd either see loads or none Smile

@archangle - from looking at the apneas they bunch together in trains of apnea followed by high flow rate breathing (i.e. hyperventilating I guess) followed by another apnea. The apneas are (from looking at the waveform) anything between 20 seconds and 80+ seconds. With a reasonably even distribution between those two values.
To be honest, looking at the waveforms creeps me out somewhat Smile
I'm 99% positive I'm not awake during these times - they go on for some time and I'm sure I'd remember them, plus there's no way I'm holding my breath for 80 seconds while awake!

@Dawei - thanks for the info. I'm definitely going to mention these CAs next time I see them. I bought the APAP to try and get a better idea of what is going on so that maybe the doctor's can help as currently they just check compliance data and then go 'see you in a year'. Which is helpful Wink
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#8
I have noticed with my Resmed s9 Autoset that the CA's are generally me opening my mouth during my sleep. I had no central apneas in my sleeps study and now my autoset tells me it is between 0.1 and 1.2 a night. Hope this information is of some help.
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#9
Check to see when those CA's are occurring. I would bet they are occurring during wakefulness, and they probably aren't of any significance. That can be proven by measuring your O2 saturation simultaneously. You probably won't see any signficant desaturation during these "centrals".

Here's my take on these so called central events. I had them, too, when I attempted to up my starting lower pressure limit. When awake and tryhing to fall asleep, we are initially uncomfortable breathing out against this too high initial pressure. We just aren't used to it. We begin to hyperventillate to overcome the pressure, and then try taking "breathing breaks" where we don't breath for several seconds, which becomes easy to do after hyperventillating. The machine records a central, though there probably isn't any desaturation. Though it doesn't need fixing since it isn't hurting you (it is only hurting your AHI), you can get rid of these "centrals" by lowering the starting pressure, or by ramping up the starting pressure from a lower pressure.

Longer periods of before falling asleep are seen with new cpap users getting used to higher starting pressures, or new masks, or both. You can also see these "centrals" when you awaken and are just laying there in bed thinking about your breathing. We tend to hyperventillate and then take "breathing breaks", since it is much easier to breath out with a deeper exhalation and then inspiration, or just not breath at all.
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#10
Is it possible that the period of time your AHI shoots up is when you are in REM sleep? Maybe you need a higher pressure for a portion of the night?
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