What is a 'Clear Airway' Event?

[dreamstream]

Can't seem to find a clear definition of a what a Clear Airway event is in SleepyHead? I've looked through the help browser in SleepyHead but it isn't defined there and google searches seem to produce conflicting definitions of what that is depending on the source. It appears from my layman's review of the data that clear air happens at the end of some kind of disruption but what kind? Central apnea? Or is that even close a definition?

[Gideon]

Clear Airway is a Central Apnea, but not monitoring effort or brainwaves ResMed decided to call it a "Clear" or "non-obstructed" Apnea

[Sleepster]

Central apnea and clear airway apnea can be considered, more or less, to be synonymous. A true central apnea can be detected during a sleep study, a chest belt reveals no effort to breathe. A CPAP machine is not sophisticated enough to do what is done in a sleep study. A CPAP machine can, when an apnea occurs, attempt to determine if the airway is open. It does this by sending pressure pulses into your airway and looking at how it responds.

[dreamstream]

Ah, okay. Thank you. See now that when you hover over the charts on the left side there are descriptions that explain each element in the graph. Clear Airway = An apnea where the airways is clear or translated for me: An apnea that is not caused by obstruction but rather the possibility that it could be a Central Apnea event.

[mesenteria]

Further, the CA's are often spurious for most of us if they are both infrequent and of short duration, say under 14 seconds.  The machine senses no effort to breathe, and eventually it registers the 'neglect' as a CA incident, but what really happened in all likelihood is that you simply began to awaken, then to turn your body, you relaxed, and fell asleep again, but you held your breath while doing all this...something exceedingly common across PAP users and most people.

[dreamstream]

Thank you. That really helps clarify things. RT did tell me that CPAP can induce CA's so was becoming a bit concerned that while I didn't have any CA's during sleep study that they were somehow showing up here. It does appear like this is some kind of mild disruption around the CA events, had 5 of them last night but they are all 12 or 10 seconds long and I feel great today so am going to assume they are some kind sleep event as you've described and not the onset of central apnea, or that's what I'll do as long as they continue to just be infrequent and AHI is is low. Thanks!

[dreamstream]

Is it possible that a 'Clear Airway' - CA event could also be open mouth breathing? Is there a way to tell if I'm using a nasal mask but breath through my mouth? Would that register in the SleepyHead data in any kind of why that I might be able to see a pattern? I'm waking up with a dry mouth in the middle of the night once in a while and I think I might breathing with my mouth open occasionally in the night.

[mesenteria]

No.  Open mouth breathing forces the machine to up its volume to compensate for the leak, which is not at all what happens when you stop breathing.  That is why the machine records leaks; it is a form of useful, rather important, feedback to help you to get the best delivery of the pressure parameters you need.  Open mouth = large leak.  And arousals....unwanted by all but the most hardy of us. 

[Sleepster]

Is it possible that a 'Clear Airway' - CA event could also be open mouth breathing?

No. But mouth-leaking is far more serious than the registering of a CA event. If air is leaking out your mouth your airway collapses and you can't breathe. You are receiving no effective CPAP therapy.

Is there a way to tell if I'm using a nasal mask but breath through my mouth?

Yes. You look at your leak rate graph. If you see extended periods of time (say 10 to 30 or more minutes) where the leak rate is elevated far above the baseline that could indicate mouth-leaking. Try a chin strap. If that doesn't work, a full face mask.

Mouth leaks can also wake you up, and if enough of that happens your night's sleep is ruined.

[Gideon]

Look at the Mouth Breathing segment of the Mask Primer.