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Obstructive Event Question
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Dreams of Green Offline

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Post: #1
Obstructive Event Question
When I look at my Sleepyhead report and see that I experienced a 12-second obstructive event, that means that for 12 seconds the machine encountered a condition that it decided it was an obstructive event. Which is why you can see that the machine always immediately increased pressure right after an obstructive event.

What I am curious about is what qualifies an obstructive event? I'm not talking about the 10-second criteria, I'm talking about what condition needs to be met for 10 seconds? In other words there is a wide range between "airway fully open" and "airway full closed", so I assume an obstructive even is based on some explicit standard? For instance, an increase of x resistance for 10 seconds? What precisely is the machine measuring to determine that something qualifies as an obstructive event, does anyone know?

BTW, for the purposes of this discussion let's agree that some events interpreted as obstructive events by the machine might be false flags and ignore that. Let's assume we're talking about real ones that are not false flags.

Thanks!
02-01-2016 06:24 PM
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Possum Offline

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Post: #2
RE: Obstructive Event Question
Our machine, the Autoset differentiates between central (open airway) and obstructive (closed airway) apneas basically by sending a series of high frequency pressure waves during the apnea. These pulses detect the state of the airway - if they cause an increase in flow rate, then it must be an OA and thus pressure is increased; if not, then it is central and will not respond to a pressure increase.

For more technical details, google "central sleep apnea detection and enhanced autoset algorithm" and you will find a scholarly article that delves in deep.
(This post was last modified: 02-01-2016 07:44 PM by Possum.)
02-01-2016 07:41 PM
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Dreams of Green Offline

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Post: #3
RE: Obstructive Event Question
Thanks, can't wait to find/read the article, I love learning about this!
02-01-2016 08:31 PM
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PaytonA Offline
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Post: #4
RE: Obstructive Event Question
(02-01-2016 07:41 PM)Possum Wrote:  Our machine, the Autoset differentiates between central (open airway) and obstructive (closed airway) apneas basically by sending a series of high frequency pressure waves during the apnea. These pulses detect the state of the airway - if they cause an increase in flow rate, then it must be an OA and thus pressure is increased; if not, then it is central and will not respond to a pressure increase.

For more technical details, google "central sleep apnea detection and enhanced autoset algorithm" and you will find a scholarly article that delves in deep.

Possum,

Might you have switched the OA and CA results? I would think that with the pressure oscillation of the FOT, if you get a corresponding flow oscillation that would say that the airway is open. If you got no corresponding flow oscillation, it would seem to me to say that the airway was closed.

Best Regards,

PaytonA
02-02-2016 12:51 PM
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Possum Offline

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Post: #5
RE: Obstructive Event Question
(02-02-2016 12:51 PM)PaytonA Wrote:  Might you have switched the OA and CA results? I would think that with the pressure oscillation of the FOT, if you get a corresponding flow oscillation that would say that the airway is open. If you got no corresponding flow oscillation, it would seem to me to say that the airway was closed.

Best Regards,

PaytonA

Dangit, just when I thought I had an intelligent, well-informed response, I get it backwards. You're correct... if the pressure pulses increase flow rate, then the airway is open, thus it's a CA.

My apologies..
02-02-2016 01:06 PM
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AlanE Offline

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Post: #6
RE: Obstructive Event Question
I bought it possum. no worries. Smile



Using FlashAir W-03 SD card in machine. Access through wifi with FlashPAP or Sleep Master utilities.

I wanted to learn Binary so I enrolled in Binary 101. I seemed to have missed the first four courses. Big Grinnie
02-02-2016 02:28 PM
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PoolQ Offline

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Post: #7
RE: Obstructive Event Question
Well this will be fun. IMHO it does not matter, because it is not exact. Let me try and explain.

When you are asleep it is not O2 that is the main concern, it is the CO2 that triggers everything. You do not want CO2 to build up in your system while you are asleep. Because of this the people that set limits on what an apnea is are trying to decide on when a person is most likely not clearing the CO2 from their system and not really when the airway is fully closed. Of course if the airway is fully closed you are not clearing CO2, but it does not have to be fully closed to not clear CO2.

Now how the heck did they figure what level they are going to use? They could have put masks on people, monitor their blood gases, and restricted their air flow. I doubt that. They could have gotten a group or people with known breathing issues and tested them at different times to see what was happening when their CO2 levels rose.

And then someone looked at all the data they got and put a margin of error on top of that and said "when sleeping, a reduction of air flow of xx% or more needs to be addressed"

They don't at this point care if it's obstructive or central, just that the restriction has reached the target level. They then decide if it's obstructive or central to figure what to do about it if anything and depending on what kind of machine they have, CPAP, APCP, BiPAP, ASV.

HOW what kind of apnea detected is with the pulses or pressure spikes. This has to do with impedance or the air way. So you have two cases 1) a long tube that is closed at the end and 2) a long tube with a fairly large drum at the end. If you try and increase the pressure in both of these cases you have 1) very little air to compress so the pressure rises quickly and 2) LOTS of air to compress so the pressure rises slowly if at all.

1) is obstructive (passage to the lungs is closed off)
2) is central (passage to the lungs is open)
(This post was last modified: 02-02-2016 03:00 PM by PoolQ.)
02-02-2016 02:59 PM
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