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At-home sleep test results - questions about central apnea
At-home sleep test results - questions about central apnea
So I took an at-home sleep test a few weeks ago and I had a few questions about the results. I'm new to this board and still absorbing all the information (started using my cpap machine yesterday but I'll save those questions for a later time Wink but it's been a great resource so far.   

The machine was called a "zMachine". It consisted of a chest belt and sensors (to measure respiratory effort), a nasal cannula (breathing), EEG (sleep state), and pulse oximeter (HR & SPO2).

The issue that prompted my visit to a sleep doctor is the following: lately, upon initiation of sleep, I would get these "jolts" that would awaken me just on the verge of sleep. At first I thought they were "hypnic jerks", but at some point, I put a pulse oximeter on my finger and saw that along with these jolts my O2 level would drop to the low 80s. I wasn't waking gasping for breath or anything, so I suspected it was sleep-onset central apnea.

The sleep test was 2 nights. The first night was ironically one of the rare nights that I slept well (subjectively speaking) and did not experience these "jolts" upon falling asleep. Still I have some questions about my results for the first night:
  • I had about 24 obstructive apneas per hour (I know that's a lot, but my focus in this post is on the centrals) and 1.5 central apneas per hour for most of the night. I remember that I slept on my left side for the majority of the night, then on my right side. The last hour of sleep I spent on my back, and my sleep was very light, and it was almost like "extra" sleep since I usually do not sleep that long. During this one hour I had 15 central apneas.
  • I have read in places here about "sleep-wake junk", that central apneas during light sleep should not be taken too seriously or something like that? Is this true? Does sleeping lightly "cause" central apneas? Or could it be that the central apneas caused the sensation of sleeping lightly?

On the second night, I had those "jolts" and I was unable to sleep at all. I wrote down the timestamps of most of the jolts and the doctor drilled into the data, and sure enough my O2 was dropping and there looked to be no respiratory effort. However the software (whatever the "zMachine" uses) scored it as an Obstructive apnea, but the doctor told me they were Central.
  • Is there a reason why the software or the doctor would've been wrong? Without going into detail, the doctor doesn't seem like a very good doctor. And it would seem an easy algorithm for the software to distinguish Obstructive versus Central: there was no breath and I believe no respiratory effort. Could the software have been seeing something the doctor was not? Unfortunately I was not able to take the data with me or even a printout of it.
  • If they were indeed central apneas, how serious are those in the transition from sleep to wake and vice versa?

Thanks for any insight you can provide!
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RE: At-home sleep test results - questions about central apnea
In the in-between wake and sleep periods, we have a tendency to hold our breath, this breath holding which occurs when we toss and turn is frequently mis-classified as centrals and is considered SWJ. I always trust a manual reading over an automated one. A key distinction is 10 seconds. It is not uncommon to see events lasting less than 10 seconds. Are they significant? It depends.

Post a copy of your dailies from SleepyHead and we can help you. If you want to know if an event is central or obstructive post a detailed 2 minute zoom of the flow rate.

1.5 CAI is a watch, but don't worry flag, 15 central events in an hour maybe, not if it's only one night. Consistently, much more likely to be significant.
Fred Bonjour - Project Manager and Lead Tester for OSCAR - Open Source CPAP Analysis Reporter 

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RE: At-home sleep test results - questions about central apnea
Thanks for the timely reply. I definitely wasn't tossing and turning during the time on my back, but I had already been asleep 8 hours and was heading into hour 9, and I normally only sleep 7 hours. I read somewhere on here about a correlation between light sleep and central apnea though I can't seem to find the thread.

The apneas on day 2 were definitely longer than 10 seconds, the doctor said some were 30 seconds. The arousal due to them kept me from sleeping at all, and this has been happening quite a bit.

Another question, a bit tangential and perhaps off-topic: the EEG showed that during my 9-hour sleep the first night, I was only in REM for 42 minutes, so about 8% of sleep time. I read that normal values are 20-25%. So that seems drastically low. Anyone have any ideas what could cause that? Google seems remarkably unhelpful about this.
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RE: At-home sleep test results - questions about central apnea
chances are you didn't sleep long enough without arousals from apnea and/or other things to reach REM stage.
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RE: At-home sleep test results - questions about central apnea
First REM cycle is somewhere near the 90 minute mark...IF we stay asleep.  Subsequent ones happen somewhat more frequently, but they also last longer, even up to 45 minutes in some cases. So, if your sleep is disjointed, so-to-speak, you may never get to REM, but your total near the five-six hour mark might be enough to help you feel reasonably well-rested.  That is, you may still feel foggy, even tired or sleepy, but you know you've 'had it' for the night, and you arise to move about and to start the day.  If so, say good-bye to those longer and healthy longer REM cycles.

I feel that tension, unresolved issues that cause 'rumination' (thinking over and over about the events or problems), and even sleeping position can lead to those leg or body jerks.  As we fall asleep, our bodies lose their tone and we might begin to fall over, or sag, or slump...and our vestibular systems react to protect us from falling.  BOOM...we're awake...AGAIN!!!

If it's positional, I know to find another position, but also to force myself into a relaxed state, particularly the upper arms, shoulders, and neck.  If my head tilts as I drift off, I'm likely to awaken and startle.
Serial Tapist
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