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False Positive on CA while Awake
#1
False Positive on CA while Awake
Reading comments on this forum about learning to read Oscar, what is False positive on CA  (Clear Airway) while CPAP user could be in awake state. Attached is my expanded Oscar reading for last night. I woke up at 5am to use the bathroom and got back to bed, but could not fall asleep & eventually got out of bed half an hour later. 
Question 1. Why is Oscar picking up all these CA while I am wake lying in bed.
Question 2. On some previous night, I got up at 4am with AHI 3.0. I went back & slept another 3 hrs. My AHI reads 6.0 in the morning.  Is this an accurate AHI? Should I be better off not going back to bed at 4am or 5 am since the sleep period loaded with CA/OA maybe doing me more harm than good?


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#2
RE: False Positive on CA while Awake
1. OSCAR reports whatever your CPAP machine reports. Your CPAP machine does not know if you are awake or sleeping; it just watches your breathing. You can easily create a CA event by holding your breath for more than 10 seconds. That often happens when you are turning over or moving around. Any events recorded while you are awake are "false" in the sense that the only events of therapeutic interest are those that occur while you are asleep.

2. AHI should accurately represent what the machine reported. If you had an AHI of 3.0 after three hours of sleep and 6.0 after an additional three hours, that suggests you had more apneas and hypopneas in the second three-hour block. And the OSCAR event chart shows exactly that.

You should get the amount of sleep you need -- don't chase the numbers. AHI is a report of your sleep quality. If you are not sleepy, then sleep hygiene suggests that you should get up. If I can't sleep, I get up.

All those CAs at the end of the night are while you were awake are sometimes referred to as "sleep-wake junk" (or SWJ) since the do not reflect your sleep. But they are counted in the AHI calculation just as if they occurred while you were sleeping. Again, your machine doesn't know if you were asleep or awake.

When posting charts, it is always best to included a full chart for the night, not just a zoomed in region. The full night's view provides a perspective lacking in a zoomed-in view.
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#3
RE: False Positive on CA while Awake
Thank you for answering my questions.

How does the machine tell the difference between OA and CA?   The flow rates chart looks similar.

I noticed from Oscar data for last few nights that majority of my apnea falls on the second half of my sleeping time. Could this be due to the circadian behavior?  Would it help though breathing exercise or meditation at 3am , before I go back to second half of my sleep?

I do back exercise with styrofoam roller on the floor before going to bed and at 3am in the morning before going back to 2nd half of my sleep. Besides helping my back, it also clears my stuffing nose.


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#4
RE: False Positive on CA while Awake
If you look at the line coming up on an apnea you will see there is a 4 hz "buzz" in it. That is the FOT, think of it as a kind of sonar that detects blockages. Blockage found means an Obstructive label, no blockage a Central label on the apnea.

Central Apnea (CA) is a term used by Resmed to flag an apnea event where an open airway is detected by the Forced Oscillation Technique (FOT), which is a 1-cm pressure oscillation at 4-times per second.
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#5
RE: False Positive on CA while Awake
Pay attention to your flow limits which I'm sure are causing you much more trouble than your central apnea, all of which I would classify as SWJ based on proximity to the start or end of a session.  

Not seeing when your flow limits are occurring, you have not shown us your flow limit chart especially in relation to your pressure changes and events so suggesting a change would be a guess.  I very much prefer to suggest changes based on data and not assumptions.
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#6
RE: False Positive on CA while Awake
Not seeing when your flow limits are occurring, you have not shown us your flow limit chart especially in relation to your pressure changes and events

Is flow limits the same as flow rate?  I don't understand the significance of the statistics on the left panel w/ Min, Med, 95% , 99.5%.

You mentioned flow limit chart in relation to pressure changes & events:   Does the attached expanded section show the detail for you?  Thanks for being patience with me.


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#7
RE: False Positive on CA while Awake
The Flow Limitation graph is a different graph than the Flow Rate.

To start, the graphs we like to see are: Events, Flow Rate, Pressure, Flow Limitation and Leak rate. Actually, when taking a Screenshot, use the F12 key and those graphs will show up.
High Flow Limitation can cause the pressure to rise. We can see that when comparing those graphs.
OpalRose
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#8
RE: False Positive on CA while Awake
This is SLEEP apnea. By definition, anything happening while you are awake does not count. if you ABSOLUTELY CERTAINLY know that something happened, you can ignore it. Having periods of time when we don't breathe while awake is pretty normal. Maybe when reading. Maybe when watching TV in a suspenseful scene. Also know that the machine cannot tell whether you are awake or asleep; it is simply reporting that it noticed a time when there was no breathing. In order to tell whether you are awake or asleep, you would need to have electrodes attached as in a sleep lab situation.
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#9
RE: False Positive on CA while Awake
Looks like there is a round button on the bottom rt corner & clicking that showed that Flow Limitation was not clicked.

Here is the screenshot. Not sure what you mean F12 will show all charts... F12 only takes screen shot for whatever is on my screen.


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#10
RE: False Positive on CA while Awake
your breathing in the zoomed image prior to the CA is about 15 bpm, fairly normal, but irregular, which implies awake breathing. Your breathing on both sides of the CA event is not a waxing/waning pattern meaning it is likely not the most common form of central apnea, complex or treatment-emergent central apnea, and its CO2-driven nature.
Do note that a bit after the CA event you seem to be panting, very rapid breathing 2-4 times the "normal" of earlier. I see no specific cause for this. Also, you have irregular "tops" on your inhalation of many of your breaths which are a sign of flow-limited breathing. one isolated area such as this is not an issue of any kind, but repeating often throughout the night is.

In OSCAR click on View / Reset Graphs / Standard to reset charts to show what we find generally to be the most informative. By default this is the order OSCAR uses unless you have changed it. If we need more, like the zooms I asked for we will ask.
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